chapter 1 biological transitions

8/11/2019 Chapter 1 Biological Transitions

1/39

Chapter 1 Biological Transitions

Chapter 2 Cognitive Transitions

Chapter 3 Social Transitions

ITheFundamentalChanges of

Adolescence


2/39


3/39

Chapter

Puberty:An Overview

The Endocrine System

What Tr iggers Puberty?

Somatic Development

Changes in Stature and the Dimensions of the Body

Sexual Maturation

The Timing and Tempo of Puberty

Indivi dual Di fferences in Pubertal Maturation

Group Di fferences in Pubertal M aturation

The Psychological and Social Impact of Puberty

The Immediate Impact of Pubert y

The Impact of Specific Pubertal Events

The Impact of Early or Late Maturation

The Scientific Study of Adolescence: EarlyMaturation and Girls Problem BehaviorActivation or Accentuation?

The Sexes: The Effects of Early MaturationEating Disorders

Physical Health and Health Care in Adolescence

1BiologicalTransitions


4/39

old joke, thereare only two

things in life that one can be sure ofdeath and taxes.Tothis brief list one might add pubertythe physicalchanges of adolescencefor, of all the developments that

take place during the second decade of li fe,the only trulyinevitable one is physical maturation. Not all adolescentsexperience identity crises, rebel against their parents, orfall head over heels in love, but virtually all undergo thebiological transitions associated with maturation intoadult reproductive capabil ity.

Puberty, however, is considerably affected by thecontext in which it occurs. Physical development i s in-fluenced by a host of environmental factors, and thetiming and rate of pubertal growth vary across regionsof the world, socioeconomic classes, ethnic groups, andhistori cal eras. In contemporary Ameri ca, the aver-agegir l reachesmenarchethe time of first menstru-ationbetween her twelfth and thirteenth birthdays.

However, among the Lumi people of New Guinea, thetypical girl does not reach menarche until after 18 yearsof age (Eveleth & Tanner, 1990). Imagine how great adifference those five years make in transforming the na-ture of adolescence. Picture how different Ameri canhigh schools would be if sexual maturation did not oc-cur unti l after graduation.

Physical and sexual maturation profoundly affect theway in which adolescents view themselves and the way inwhich they are viewed and treated by others. Yet the so-

Part I The Fundamental Changes of Adolescence22

cial environment exerts a tremendous impact on themeaning of puberty and on its psychological and socialconsequences; indeed,as you will read in this chapter, thesocial environment even affects the timingof puberty(i .e.,whether a person matures early or late). In some so-

cieties, pubertal maturation brings with i t a series ofcomplex ini tiation ri tes that mark the passage of theyoung person into adulthood socially as well as physi-cally. In other societies, recognition of the physical trans-formation from child into adult takes more subtle forms.Parents may merely remark,Our little boy has become aman, when they discover that he needs to shave.Early orlate maturation may be cause for celebration or cause forconcern, depending on what is admired or derogated ina given peer group at a given point in time. In the fifthgrade,developing breasts may be a source of embarrass-ment;but in the ninth grade, it may be just as embarrass-ing notto have developed breasts.

In sum, even the most universal aspect of adoles-

cence

puberty

is hardly universal in its impact onthe young person. In this chapter,we will examine justhow and why the environment in which adolescents de-velop exerts its influence even on something as funda-mental as puberty.

PUBERTY: AN OVERVIEW

Pubertyderives from the Latin word pubertas, whichmeans adult. Technically, the term refers to the period

during which an individual becomes ca-pable of sexual reproduction; that is, itdenotes the series of biological changes

leading up to reproductive capability.More broadly speaking, however, pu-berty encompasses all the physicalchanges that occur in the growing girl orboy as the individual passes from child-hood into adulthood.

The following are the five chief phys-ical manifestations of puberty (Mar-shall , 1978):

1. A rapid accelerati on in growth, re-sulting in dramatic increases inboth height and weight

2. Thedevelopment of primary sexcharacteristics, including the furtherdevelopment of the gonads,or sexglands,which are the testes in malesand the ovaries in females

According to an

Although pubert y is a uni versal feature of adolescence, individuals developphysically at dif ferent ages and at dif ferent rates. (David Young Wolff/PhotoEdit)


5/39

Hormonal levels are set at a certain point, just as youmight set a thermostat at a certain temperature.By sett ingyour rooms thermostat at 60F, you are instructing yourheating system to go into action when the temperaturefalls below this level. Similarly, when a part icular hor-

monal level in your body dips below the endocrine sys-tems set point for that hormone, secretion of the hor-mone increases; when the level reaches the set point,secretion temporari ly stops. And, as is the case with athermostat, the setting level, or set point, for a part icularhormone can be adjusted up or down, depending on en-vironmental or internal bodily conditions.

Such afeedback loopbecomes increasingly importantat the onset of puberty.Long before early adolescencein fact,during infancya feedback loop develops involv-ing thepituitary gland(which controls hormone levels ingeneral), the hypothalamus (the part of the brain thatcontrols the pituitary gland), and thegonads(in males,the testes; in females, the ovaries), a feedback loop known

as the HPG axis (for hypothalamus, pituitary, gonads).The gonads release the sex hormonesandrogensandestrogens (see figure 1.1). Although one typicall ythinks of androgens as male hormones and estrogensas female hormones,both types of hormones are pro-duced by each sex,and both are present in males and fe-males at bir th. During adolescence, however, the aver-age male produces more androgens than estrogens,and the average female produces more estrogens thanandrogens (Petersen & Taylor, 1980).

The hypothalamus responds to the levels of sex hor-mones circulating in the body.Your HPG axis is set tomaintain certain levels of androgens and estrogens.

When these levels fall below the set points, the hypo-thalamus no longer inhibits the pitui tary, thus permi t-ting it to stimulate the release of sex hormones by thegonads and other, puberty-related hormones by the ad-renal gland. When sex-hormone levels reach the setpoint, the hypothalamus responds by inhibi ting itsstimulation of the pituitary gland.

Hormones play two very different roles in adolescentdevelopment; they perform both an organizational roleand an activational role(Coe, Hayashi, & Levine, 1988;Collaer & Hines, 1995). Long before adolescenceinfact, prenatallyhormones shape, or organize, thebrain in ways that may not be manifested in behavioruntil childhood or even adolescence. Generally speak-

ing,until about eight weeks after conception, the humanbrain i s feminine unless and until it is exposed to cer-tain masculinizing hormones, such as testosterone.Because levels of testosterone are higher among males

3. The development of secondary sex characteri stics,which involves changes in the genitals and breasts;the growth of pubic, facial, and body hair ; and thefurther development of the sex organs.

4. Changes in body composit ionspecifically, in the

quanti ty and distr ibution of fat and muscle5. Changes in the circulatory and respiratory systems,

which lead to increased strength and tolerance forexercise

Each of these sets of changes is the result of develop-ments in the endocrine and central nervous systems,many of which begin years before the external signs ofpuberty are evidentsome occur even before birth.

The Endocr ine System

Theendocrine systemproduces,circulates,and regulateslevels of hormones in the body. Hormones are highlyspecialized substances secreted by one or more endocrineglands.Glandsare organs that stimulate particular parts

of the body to respond in specific ways.Just as specializedhormones carry messages to particular cells in the body,so are the bodys cells designed to receive hormonal mes-sages selectively. For example,one of the many effects ofthe hormone adrenaline,secreted by the adrenal gland, isto stimulate the heart to increase its activity.The heart re-sponds to adrenaline but not to all other hormones.

Puberty may appear to be rather sudden, judgingfrom its external signs, but, in fact, it is part of a gradualprocess that begins at conception (Petersen & Taylor,1980). You may be surprised to learn that no new hor-mones are produced and no new bodily systems developat puberty.Rather,some hormones that have been pres-ent since before bir th increase, and others decrease.

The endocrine system receives its instructions to in-crease or decrease circulating levels of particular hor-mones from the central nervous systemchiefly, thebrain. The system works somewhat like a thermostat.

RECAP

The termpuberty refers to the physical changes that oc-cur in the growing gir l or boy as the indi vidual passes

from childhood into adulthood. The chief physical man-ifestat ions are the growth spurt, the further developmentof the gonads, the development of secondary sex charac-teristi cs, changes in body composit ion, and changes incirculation and respirati on.

Chapter 1 Biological Transiti ons 23


6/39

than females while the brain is developing, males, ingeneral, end up with a more masculinized brain thanfemales.This sex difference in brain organization prede-termines certain patterns of behavior, many of whichmay not actually appear until much later (Collaer &Hines,1995).Studies of sex di fferences in aggression, forexample, show that, even though some of these differ-ences may not appear until adolescence, they likely re-sult from the impact of prenatal hormones, rather thanfrom hormonal changes at puberty.

In other words, the presence or absence of certainhormones early in life may program the brain andnervous system to develop in certain ways later on. Be-cause we may not see the resulting changes in behavioruntil adolescence, it is easy to conclude mistakenly thatthe behaviors result from hormonal changes specific topuberty. In reali ty, however, exposure to certain hor-mones before bir th may set a sort of alarm clock,whichdoes not go off until adolescence. Just because the

alarm clock rings at the same time that puberty beginsdoes not mean that puberty caused the alarm to go off.


Other changes in behavior at adolescence occur,however, because of changes in hormone levels at pu-berty; these hormonal changes are said to activatethechanges in behavior. For instance, the increase in cer-tain hormones at puberty is thought to stimulate thedevelopment of secondary sex characteristi cs, such asthe growth of pubic hair. Other hormonal changes atadolescence, controlled by the adrenal gland,may stim-ulate an increase in indivi duals sex drive (McClintock& Herdt, 1996).

Still other changes during puberty are likely to be re-sults of an interactionbetween the organizational andactivational effects of hormones (Collaer & Hines,1995). Hormones that are present during the develop-ment of the fetus may organize a certain set of behav-iors (for example, the brain may be set up to have uslater engage in sexual behavior), but certain changes inthose hormones at puberty may be needed to activatethe pattern; that is, indivi duals may not become moti -

vated to engage in sex until puberty.

What Triggers Puber ty?

Although the HPG axis is active long beforeadolescencebefore birth, in factit is relatively quietduring much of childhood. Something happens duringmiddle childhood, though, that reawakens the HPGaxis and signals it that the body is ready for puberty.

The timing of pubert y is affacted by experience as well asheredity.Exercise can affect the onset of pubert y. (Li-Hua Lan/The Image Works)

Hypothalamus

Pituitarygland

Gonads

Androgens

Estrogens

LH-RF (luteinizinghormone-releasingfactor) and FSH-RF(follicle-stimulatinghormone-releasingfactor) stimulatepituitary gland.

LH (luteinizinghormone) and FSH(follicle-stimulatinghormone) stimulategonads.

Hypothalamusmonitors levelsof androgensand estrogens.

(Testes inmales, ovariesin females)

Figur e 1.1 Levels of sex hormones are regulated by a feedbacksystem composed of the hypothalamus, pitu itary gland,andgonads. (Grumbach,Roth, Kaplan,& Kelch,1974)


7/39

SOMATIC DEVELOP MENT

The effects of the endrocrinological changes of pubertyon the adolescents body are remarkable. Consider the

dramatic changes in physical appearance that occurduring the short span of early adolescence. One enterspuberty looking like a child but within four years or sohas the physical appearance of a young adult . Duringthis relatively brief period of time, the average individ-ual grows nearly 12 inches taller, matures sexually,anddevelops an adult-proportioned body.

Changes in Stature and the D imensions

of the Body

The simultaneous release of growth hormone, thyroidhormones, and androgens stimulates rapid accelera-tion in height and weight. This dramatic increase in

stature is referred to as the adolescent growth spurt.What is most incredible about the adolescent growthspurt i s not so much the absolute gain of height andweight that typically occurs but the speed with whichthe increases take place. Think for a moment of howquickly very young children grow.At the time ofpeakheight velocitythe time at which the adolescent isgrowing most rapidlyhe or she is growing at thesame rate as a toddler. For boys, peak height velocityaverages about 4.1 inches (10.5 centimeters) per year;for girls, it averages about 3.5 inches (9.0 centimeters)(J. Tanner, 1972).

Figure 1.2 shows just how remarkable the growth

spurt is in terms of height. The graph on the left pres-ents information on absolute height and indicatesthat, as you would expect, the average indivi dual in-creases in height throughout infancy, childhood, andadolescence. As you can see, there is li tt le gain in


RECAP

The onset of puberty is regulated by a feedback loop inthe endocrine system, called the HPG axis, involving thehypothalamus, the pituit ary, and the gonadsovariesin females, testes in males. Increases in some hormonesand decreases in others, as a result of acti vi ty along theHPG axis, result in the internal and external changesassociated wit h puberty. Sex hormones play two roles inadolescent development: organizational and acti va-ti onal. Long before pubert y, they organize the brain inways that are not mani fested unt il adolescence. And at

puberty, they acti vate new patterns of behavior. There isincreasing evidence that ri sing levels of a protein pro-duced by fat cells, leptin , may signal the hypothalamusto set the hormonal changes of pubert y in motion.

Food for Thought

In a study of monkeys that was donesome years ago, it was found that malemonkeys who had been castrated ( i.e.,

had their testes removed) shortly after bir th sti llshowed the onset of many of the changes in sexualbehavior at adolescence normal ly observed amongmales of thi s species (Coe et al., 1988). How doesthe distinction between the organizational and ac-ti vati onal effects of hormones help account for this?

Although scientists are not entirely certain, there is in-creasing evidence that rising levels of a protein producedby fat cells, leptin, may be the most important signal(Spear, 2000). This idea is consistent wi th observationsthat individuals may not go through puberty until theyhave accumulated a certain amount of body fat and isconsistent with research showing that stress, il lness, nu-triti onal deficiencies, excessive exercise, and excessivethinness can all delay the onset of puberty (Frisch,1983;McClintock, 1980). The signal carr ied by rising levels ofleptin instructs the hypothalamus both to stop doingthings that have been inhibit ing puberty and to start do-ing things that set i t i n motion (Spear, 2000). As a resultof both of these processes, the hypothalamus initiates acascade of hormonal events that ul timately result in thesexual maturation of the individual.

During and just before puberty, the pitui tary alsosecretes hormones that act on the thyroid and on theadrenal cortex, as well as hormones that stimulate

overall bodily growth. The release of these substancesis also under the control of the hypothalamus. Thethyroid and adrenal cortex, in turn, secrete hormonesthat cause various physical (somatic) changes to takeplace at puberty. Research also indi cates that earlyfeelings of sexual attraction to othersmost i ndivid-uals report that their first sexual att racti on took placearound age 10, before they went through pubertymay be stimulated by maturation of the adrenalglands, called adrenarche (McClintock & Herdt,1996). Changes at puberty in the brain system thatregulates the adrenal gland are also impor tant becausethis is the brain system that controls how we respondto stress (Spear, 2000).


8/39

height after the age of 18. But look at the ri ght-handgraph, which shows the average increase in height peryear(i .e., the rateof change) over the same age span.Here you can see the acceleration in height at the timeof peak height velocity.

Figure 1.2 also indicates quite clearly that thegrowth spurt occurs, on the average, about two yearsearl ier among gir ls than among boys. In general, asyou can see by comparing the two graphs,boys tend tobe somewhat taller than gir ls before age 11; then girl stend to be taller than boys between ages 11 and 13; fi-nally, boys tend to be taller than gir ls from about age14 on. You may remember what this was li ke duringfifth and sixth grades. Sex di fferences in height can bea concern for many young adolescents when they be-gin socializing with members of the opposite sex, es-pecially if they are tall , early-maturing girls or short,late-maturing boys.

Duri ng puberty, the composit ion of the skeletalstructure also changes; bones become harder, moredense, and more bri tt le. One marker of the conclusionof puberty is the closing of the ends of the long bones in

the body, which terminates growth in height. Interest-ingly, there are ethnic differences in some of these skele-tal changes, with bone density increasing significantlymore during puberty among African American thanamong whi te youngsters.Some experts beli eve that this


ethnic difference in adolescence may account for thefact that, during adulthood, Afri can American womenare less likely than white women to develop osteoporo-sis, and they have fewer bone fractures (Gilsanz, Roe,Mora,Costin, & Goodman, 1991).

Much of the height gain dur ing puberty results froman increase in torso length rather than in leg length. Thesequence in which various parts of the body grow isfairl y regular. Extremiti esthe head, hands, andfeet

are the first to accelerate in growth.Then acceler-ated growth occurs in the arms and legs, fol lowed bytorso and shoulder growth. In concrete terms, a boystops growing out of his trousers (at least in length) ayear before he stops growing out of his jackets (J.Tanner, 1972, p.5).

Young adolescents often appear to be out of propor-tion physicallyas though their noses or legs weregrowing faster than the rest of them. Its not an opti calil lusion. The parts of the body do not all grow at thesame rate or at the same time during puberty. Thisasynchronicity in growthcan lead to an appearance ofawkwardness or gawkiness in the young adolescent,

who may be embarrassed by the unmatched acceleratedgrowth of various parts of the body. It is probably lit tleconsolation for the young adolescent to be told that anaesthetic balance probably will be restored within a fewyears; nevertheless, this is what usually happens.

Height(cm)

Heightgain(cm/yr)

190

180

170

160150

140

130

120

110

100

90

80

70

60

50

1 3 5 7 9 11 13 15 17 19

24232221201918

1716151413121110987654321

1 3 5 7 9 11 13 15 17 19Age (years)Age (years)

Boy

Girl

Boy

Girl

Figur e 1.2 Left: height ( in cent imeters) at di fferent ages for the average male and female youngster. Right: gain in height per year(i n centimeters) for the average male and female youngster. Note the adolescent growth spurt. (Adapted from Marshall, 1978)


9/39

Although most girl s diet unnecessari ly dur ing this timein response to the increase in body fat, the youngwomen who are most susceptible to feelings of dissatis-faction with their bodies duri ng this phase of develop-ment are those who mature early, begin dating early,and come from relatively more affluent famil ies (Dorn-busch et al., 1981; Smolak, Levine, & Gralen, 1993).African American females seem less vulnerable to thesefeelings of body dissati sfaction than other gir ls, and

consequently they are less likely to diet, presumably be-cause of ethni c differences in conceptions of the idealbody type. Even among African American youngsters,however, dieti ng is common in early adolescence(Halpern & Udry, 1994). Many studies point to adoles-cence as the period of greatest risk for the developmentof eati ng disorders,such as anorexia and bulimia.

Accompanying the gains in strength that occur dur-ing early adolescence are increases in the size and ca-pacity of the heart and lungs and, consequently, in exer-cise tolerance. In all these areas, the rate and magnitudeof the gains favor males over females. By the end of pu-berty, boys are stronger, have larger hearts and lungsrelative to their size, a higher systolic blood pressure,a

lower resting heart rate, a greater capacity for carr yingoxygen to the blood, . . . a greater power for neutraliz-ing the chemical products of muscular exercise, such aslactic acid, higher blood hemoglobin, and more redblood cell s (Petersen & Taylor, 1980,p. 129).

The spurt in height during adolescence is accompa-nied by an increase in weight, which results from an in-crease in both muscle and fat.However, there are impor-tant sex differences along these latter two dimensions.Inboth sexes, muscular development i s rapid and closelyparallels skeletal growth, but muscle tissue grows fasterin boys than in girls (see figure 1.3). Body fat increasesfor both sexes during puberty, but more so for femalesthan for males and at a somewhat faster rate for girls,es-pecially during the years just before puberty. For boys,there is actually a slight decline in body fat just before pu-berty.The result of these sex differences in growth is thatboys finish adolescence with a muscle-to-fat ratio ofabout 3:1,but the comparable ratio for gir ls is approxi-mately 5:4. This has important implications for under-standing why sex differences in strength and athletic abil-ity often appear for the first time during adolescence.According to one estimate, about half of the sex differ-ence in physical performance during early adolescenceresults simply from the difference in body fat (Smoll &Schutz, 1990). Before puberty,there are relatively few sexdifferences in muscle development and only slight sexdifferences in body fat.

The rapid increase in body fat that occurs among fe-males in early adolescence frequently prompts younggirls to become overly concerned about their weighteven when their weight is within the normal range fortheir height and age (Smolak, Levine, & Gralen, 1993).


25

20

15

10

5

4 6 8 10 12 14 16 18

16

14

12

10

8

6

4

2

4 6 8 10 12 14 16 18Age (years) Age (years)

Musclemass(kg)

Bodyfat(kg)

Male

Female

Male

Female

Figur e 1.3 Dur ing preadolescence, important sex differences emerge in body composition that cont inue through adolescence. These

graphs reflect muscle and body fat for indi viduals of average height at each age. Note the changes in muscle mass(left) and body fat(right). (Adapted from Gumbach et al., 1974)


10/39

Food for Thought

How are the somati c changes of pu-bert y di fferent for males and females?Why might some of these changes make

adolescents feel awkward about or unhappy wi ththeir body? Why might body dissati sfaction begreater among adolescent gir ls than boys? Is this

biological, cultu ral, or a combinati on of the two?

It is tempting to attribute these sex differences purelyto hormonal factors, because androgens,which are pres-ent at higher levels in the prenatal environments of malesversus females, and which increase during puberty inmales at a much faster rate than in females, are closelylinked to growth along these physical dimensions.In ad-dit ion, with age, such environmental factors as diet andexercise become increasingly important influences on sexdifferences in physical performance (Smoll & Schutz,1990). As Petersen and Taylor (1980) point out, there arestrong social pressures on girls to curtail masculine ac-tivitiesincluding some forms of exerciseat adoles-cence, and studies show that girls are more likely thanboys to markedly reduce their physical activity in preado-lescence, with a very large proportion of adolescent girlsfailing to meet national guidelines for physical activity(Goran et al., 1998;Savage & Scott,1998).Moreover,ado-lescent girls diets, especially those of African Americangirls,are generally less adequate nutritionally than the di-

ets of boys, particularly in important minerals, such asiron (Johnson, Johnson, Wang, Smiciklas-Wright, &Guthrie,1994). Both factors could result in sex differencesin muscular development and exercise tolerance. Thus,sex differences in physical abili ty are influenced by a vari-ety of factors, of which hormonal differences are but onepart of an extremely complicated picture. Along withmany other of the bodys organs, the brain changes insize, structure,and function at puberty, a series of devel-opments that we will discuss in chapter 2.

28

Sexual Matur ation

Puberty brings with i t a series of developments associ-ated with sexual maturation. In both boys and girls,the development of thesecondary sex characteristicsis typicall y divided into five stages,often calledTanner

Table 1.1 The sequence of physical changes at pubert y

Source: Goldstein, B. (1976). Int roduction to human sexuali ty. Belmont, CA: Star.

Boys Girls

Age of First Appearance Age of First AppearanceCharacteristic (Years) Characteristic (Years)

1. Growth of testes, 101312 1. Growth of breasts 713scrotal sac

2. Growth of pubic hair 1015 2. Growth of pubic hair 714

3. Body growth 101216 3. Body growth 91214

12

4. Growth of penis 111412 4. Menarche 101612

5. Change in voice About the same time as 5. Underarm hair About two years after(growth of larynx) penis growth pubic hair

6. Facial and underarm About two years after 6. Oil- and sweat- About the same timehair pubic hair appears producing glands underarm hair

(acne occurs when

glands are clogged)

7. Oil - and sweat-producing About the same time asglands, acne underarm hair

RECAP

The dramatic increase in stature that occurs during pu-berty is referred to as the adolescent growth spurt . On av-erage, girls experience the growth spurt about two yearsearl ier than boys. Important changes also take place in the

relati ve proport ions of body fat and muscle, and thesechanges leave boys relat ively more muscular and with alower proportion of body fat. Many gir ls react to the in-crease in body fat at puberty by dieting unnecessari ly.

Part I The Fundamental Changes of Adolescence


11/39

spurt in height begins, accompanied by growth of thepenis and further development of pubic hairnow ofa coarser texture and darker color. The five Tannerstages of penis and pubic hair growth i n boys are

shown in figure 1.4.The emergence of facial hairfirst at the corners of

the upper l ip, next across the upper l ip, then at the up-per parts of the cheeks and in the midline below thelower lip, and finally along the sides of the face and the

stages, after the British pediatrician who devised thecategori zati on system.

Sexual Maturation in Boys The sequence of de-

velopments in secondary sex characteristics amongboys is fair ly orderly (see table 1.1). Generally, the firststages of puberty involve growth of the testes andscrotum, accompanied by the first appearance of pu-bic hair. Approximately one year l ater, the growth


1. 2. 3. 4. 5.

PenisScrotumGlans (Head)

Testes

Penis and Scrotum

Stage 1: There is no true pubic hair, although there may be a fine velus over the pubes similarto that over other parts of the abdomen.Stage 2: Sparse growth of lightly pigmented hair, which is usually straight or only slightlycurled. This usually begins at either side of the base of the penis.Stage 3: The hair spreads over the pubic symphysis and is considerably darker and coarser andusually more curled.Stage 4: The hair is now adult in character but covers an area considerably smaller than in

most adults. There is no spread to the medial surface of the thighs.Stage 5: The hair is distributed in an inverse triangle as in the female. It has spread to themedial surface of the thighs but not up the linea alba or elsewhere above the base of thetriangle.

Pubic Hair

Stage 1: The infantile state that persists from birth until puberty begins. During this timethe genitalia increase slightly in overall size but there is li ttle change in generalappearance.Stage 2: The scrotum has begun to enlarge, and there is some reddening and change intexture of the scrotal skin.Stage 3: The penis has increased in length and there is a smaller increase in breadth.

There has been further growth of the scrotum.Stage 4: The length and breadth of the penis have increased further and the glans hasdeveloped. The scrotum is further enlarged and the scrotal skin has become darker.Stage 5: The genitalia are adult in size and shape. The appearance of the genitalia maysatisfy the criteria for one of these stages for a considerable time before the penis andscrotum are sufficiently developed to be classified as belonging to the next stage.

1. 2. 3. 4. 5.

Figur e 1.4 The five pubertal stages of peni le and pubic hair growth. (Morris & Udry,1980)


12/39

RECAP

One of the most important physical changes of pubert yis the development of secondary sex characteri sticsthe changes in outward appearance that signal the onsetof reproductive matur it y. These changes include thegrowth of pubic hair, changes in the appearance of thesex organs, and breast development.

Food for Thought

Think about the changes in secondarysex characteristi cs that take place dur -

ing pubert y. Why might humans haveevolved so that puberty occurs on the outside ofthe body as well as internall y?

lower border of the chinand body hair are relativelylate developments in the pubertal process. The same istrue for the deepening of the voice, which is gradualand generally does not occur until very late adoles-cence. Dur ing puberty, there are changes in the skin as

well ; the skin becomes rougher, especially around theupper arms and thighs, and there is increased develop-ment of the sweat glands,which often gives rise to acne,skin eruptions, and increased oili ness of the skin.

Dur ing puberty, there are sli ght changes in themale breastto the consternation and embarrass-ment of many boys. Breast development is largely in-fluenced by the estrogen hormones. Both estrogensand androgens are present in both sexes and increasein both sexes at puberty, although in di fferi ngamounts. In the male adolescent, the areola (the areaaround the nipple) increases in size, and the nipplebecomes more prominent. Some boys show a slightenlargement of the breast, although in most cases this

development is temporary.Other, internal changes occur that are impor tant el-

ements of sexual maturation.At the time that the penisdevelops, the seminal vesicles, the prostate, and thebilbo-urethral glands also enlarge and develop. Thefirst ejaculation of seminal fluid generally occurs aboutone year after the beginning of accelerated penisgrowth, although this is often determined culturally,rather than biologicall y,since for many boys first ejacu-lation occurs as a result of masturbation (J. Tanner,1972). One interesting observation about the timingand sequence of pubertal changes in boys is that boysare generally fert il e (i .e., capable of fatheri ng a child)

before they have developed an adultlike appearance.The opposite is true for gir ls.

Sexual Maturation in Girls The sequence of devel-opment of secondary sex characteristi cs among girls(shown in Table 1.1) is somewhat less regular than it isamong boys. Generally, the first sign of sexual matura-tion is the elevation of the breastthe emergence ofthe so-called breast bud. In about one-third of all ado-lescent girl s, however, the appearance of pubic hair pre-cedes breast development. The development of pubichair follows a sequence similar to that in malesgen-erally from sparse, downy, light-colored hair to moredense, curled, coarse, darker hair. Breast development

often occurs concurrently and generally proceedsthrough several stages. In the bud stage, the areolawidens,and the breast and nipple are elevated as a smallmound. In the middle stages, the areola and nipple be-


come distinct from the breast and project beyond thebreast contour. In the final stages, the areola is recessedto the contour of the breast, and only the nipple is ele-vated. The female breast undergoes these changes atpuberty regardless of changes in breast size. Changes in

the shape and definition of the areola and nipple are farbetter indicators of sexual maturation among adoles-cent girls than is breast growth alone. The five Tannerstages of breast and pubic hair growth in gir ls areshown in figure 1.5.

As is the case among boys, puberty brings importantinternal changes for adolescent girl that are associatedwith the development of reproductive capacity. In gir ls,these changes involve the development and growth of theuterus,vagina,and other aspects of the reproductive sys-tem. In addition, the labia and clitoris enlarge.

As is apparent in table 1.1, the growth spurt is li kelyto occur during the early and middle stages of breastand pubic hair development. Menarche, the beginning

of menstruation, is a relati vely late development,which reflects the culmination of a long seri es of hor-monal changes (Dorn et al., 1999). Hence, it i s incor-rect to use menarche as a marker for the onset of pu-berty among girl s. A great deal of pubertaldevelopment has taken place long before the adoles-cent girl begins to menstruate. Generally, ful l repro-ductive function does not occur unt il several years af-ter menarche, and regular ovulati on follows menarcheby about two years (Hafetz, 1976). Unl ike boys, there-fore, girls generally appear physicall y mature beforethey are capable of becoming pregnant.


13/39


Stage 1. No breast development.

Stage 2. The first sign of breast developmenthas appeared. This stage is sometimesreferred to as the breast budding stage.Some palpable breast tissue under thenipple, the flat area of the nipple(areola) may be somewhat enlarged.

Stage 3. The breast is more distinct althoughthere is no separation between contoursof the two breasts.

Stage 4. The breast is further enlarged andthere is greater contour distinction.

The nipple including the areola formsa secondary mound on the breast.

Stage 5. Size may vary in the mature stage.The breast is fully developed. Thecontours are distinct and the areola

has receded into the general contour of the breast.

Pubic Hair

Breasts

Stage 1. No pubic hair.

Stage 2. There is a small amount of long

pubic hair chiefly along vaginal lips.

Stage 3. Hair is darker, coarser, and curlierand spreads sparsely over skin around

vaginal lips.

Stage 4. Hair is now adult in type, but area covered is smaller than in most adults. There is no pubic hair on the inside of the thighs.

Stage 5. Hair is adult in type, distributed asan inverse triangle. There may be hairon the inside of the thighs.

1.

2.

3.

4.

5.

2.1. 3.

5.4.

Figur e 1.5 The five pubert al stages for breast and pubic hair growth. (Marshall & Tanner, 1969.Reprinted by permission of

BMJ publishing Group)


14/39

THE TIMING AND TEMP O

OF PUBERTY

You may have noted that, thus far,no mention has beenmade about the normal ages at which various puber-tal changes are likely to take place. The truth is that thevariations in the timing of puberty (the age at whichpuberty begins) and in the tempo of puberty (the rateat which maturation occurs) are so great that it is mis-leading to talk even about average ages.

The onset of puberty can occur as early as age 7 yearsin girls and 91/2 in boys, or as late as 13 in girls and 13

1/2in boys. In gir ls, the interval between the first sign ofpuberty and complete physical maturation can be asshort as a year and a half or as long as six years.In boys,the comparable interval ranges from about two years tofive years (J. Tanner, 1972). Within a totall y normalpopulation of young adolescents,some individuals wil lhave completed the entire sequence of pubertal changes

before others have even begun. In more concrete terms,it is possible for an early-maturing, fast-matur ingyoungster to complete pubertal maturation by the ageof 10 or 11two years before a late-maturing young-ster has even begun puberty and seven years before alate-maturi ng, slow-maturing youngster has maturedcompletely.

There is no relation between the age at which pu-berty begins and the rate at which pubertal develop-ment proceeds.The timing of puberty may have a small


effect on the ultimate adult stature or bodily dimen-sions of the individual, with late maturers, on average,being taller than early maturers as adults,and early ma-turers, on average, being somewhat heavierat leastamong females (St. George, Williams, & Silva, 1994).Adult height and weight are far more strongly corre-lated with height and weight before childhood thanwith the timing of puberty, however.

Many people believe that there are ethnic differencesin the timing and rate of pubertal maturation, althoughthe results of studies in this area have been inconclu-sive. One large-scale study of U.S. youngsters doesindicate, however, that African American females maymature significantly earlier than their white counter-parts (the study did not include enough youngstersfrom other ethnic groups to make statistical compar-isons). For example, whereas the average age of menar-che among white U.S. girl s is closer to 13, amongAfri can American girl s, it is closer to 12. And,as figure

1.6 shows, more than 27 percent of African Americangirl s, but less than 7 percent of white girls,have enteredpuberty by age 7 (Herman-Giddens et al., 1997). Al-though the reasons for this ethnic difference are notknown, one possibi li ty i s that African-American girlsare more frequently exposed to chemicals in the envi-ronment, such as synthetic hormones,which may stim-ulate earlier puberty.

What factors underlie the tremendous variationsin the timing and tempo of pubert y? Why do some

0

10

20

30

40

50

60

70

80

90

100

%

3 4 5 6

Age (years)

7 8 9 10 11 12

1.0 3.1 0.9

7.6

1.9

5.73.7

14.3

6.7

27.2

14.7

48.3

38.2

77.4

67.9

94.688.0

98.496.6

100.0

White

African American

Figur e 1.6 Prevalence of Afr ican Ameri can and white gir ls at different ages who show signs of eit her breast development or pubichair. (Herman-Giddens et al., 1997)


15/39

For example, girls in ballet companies or i n other ri g-orous traini ng programs often mature later than theirpeers (Fri sch, 1983). Generally speaking, then, aftergenetic factors, an important determinant of the on-set of puberty is the overall physical well-being of the

individual from conception through preadolescence(Marshall , 1978).Interestingly, a number of studies suggest that so-

cial as well as physical factors in the environment in-fluence the onset of maturati on, especiall y in girls.Several studies, for example, have found that pubertymay occur somewhat earlier among girls who havegrown up in less cohesive, or more confli ct-r idden,family environments or in households in which astepfather i s present (e.g., Ell is & Garber, 2000; Ell is,McFadyen-Ketchum, Dodge, Pett it , & Bates, 1999;Graber, Brooks-Gunn, & Warren, 1995; Moffit t, Caspi,Belsky, & Silva, 1992; Steinberg, 1988; Surbey, 1990).One explanation for the finding that distant family re-

lations may accelerate pubertal maturati on is that dis-tance in the family may induce a very small amount ofstress, which, in turn, may affect hormonal secreti ons

individuals mature relatively early and others rela-ti vely late?

Researchers who study variability in the onset andtiming of puberty approach the issue in two ways. Onestrategy involves the study of differences among indi-

viduals (that is, studying why one individual maturesearl ier or faster than another) . The other involves thestudy of differences among groups of adolescents (thatis, studying why puberty occurs earl ier or more rapidlyin certain populations than in others). Both sets ofstudies point to both genetic and environmental influ-ences on the timing and tempo of puberty.

I ndividual D if ferences

in Pubertal Maturation

Differences in the timing and rate of puberty amongindividuals growing up in the same general environ-ment result chiefly, but not exclusively, from genetic

factors. Comparisons between pairs individuals whoare genetically identi cal (i denti cal twins) and pairs whoare not reveal patterns of similari ty in pubertal matura-tion indicating that the timing and tempo of an indi-viduals pubertal maturation are largely inherited(Marshall , 1978).

Despite this powerful i nfluence of genetic factors,the environment plays an important role. In all likeli -hood, every individual inheri ts a predisposit ion to de-velop at a certain rate and to begin pubertal maturationat a certain time. But this predisposition is best thoughtof as upper and lower age limits, not a fixed absolute.Whether the genetic predisposition that each person

has to mature around a given age is actually realized,and the time within the predisposed age boundaries atwhich he or she actually goes through puberty,are sub-ject to the influence of the environment. In this respect,the timing and rate of pubertal maturation are theproduct of an interaction between nature and nurture,between ones genetic makeup and the environmentalcondit ions under which one has developed.

By far the two most important environmental in-fluences on pubertal maturation are nutrition andhealth. Puberty occurs earl ier among indivi duals whoare better nourished throughout their prenatal, in-fant,and childhood years.Not surpr isingly, then,girlswho are taller or heavier than their peers mature ear-li er (St. George et al., 1994). In contrast, delayed pu-berty is more likely to occur among individuals witha history of protein and/or caloric deficiency.Chronicillness during childhood and adolescence is also asso-ciated with delayed puberty, as is excessive exercise.


The age at which adolescents mature physically varies aroundthe world. On average, teenagers in highly industr ial ized coun-tr ies, such as Japan,mature earl ier than their counterpar ts in de-veloping nati ons, where health and nutr it ional problems slowphysical growth. (R.M. Collins, II I/ Image Works)


16/39

in the adolescent (Graber et al., 1995). Puberty may besped up by smallamounts of stress; a great deal ofstress, however, is likely to slow maturation (Ell is &

Garber, 2000). In addition, the presence of a stepfathermay expose the adolescent gir l topheromones(chem-icals secreted by animals that stimulate certain behav-iors in other members of the species) that stimulatepubertal maturation. In general, among humans andother mammals,li ving in proximity to ones close bio-logical relatives appears to slow the process of puber-tal maturati on, whereas exposure to unrelated mem-bers of the opposite sex may accelerate it (I zard, 1990;Surbey, 1990).

Although it may seem surpr ising that something asbiological as puberty can be influenced by factors inour social environment, scientists have long knownthat our social relati onships can indeed affect our bio-logical functioning. One of the best-known examplesof this is that women who l ive togethersuch as dor-mitory roommatesfind that their menstrual peri-ods begin to synchronize over t ime (Graham, 1991;McClintock, 1980).


Group D if ferences in Puber tal Maturati on

Researchers typically study group differences in pu-

berty by comparing average ages of menarche in differ-ent regions. Most of these studies have indicated thatgenetic factors play an extremely small role in deter-mining group differences in pubertal maturation(Eveleth & Tanner, 1990). Di fferences among countriesin the average rate and timing of puberty are morelikely to reflect differences in their environments thandif ferences in their populations gene pools (Morabia,Costanza, & World Health Organization, 1998).

The influence of the broader environment on the tim-ing and tempo of puberty can be seen in more concreteterms by looking at three sorts of group comparisons: (1)comparisons of the average age of menarche across coun-tr ies, (2) comparisons among socioeconomic groupswithin a country, and (3) comparisons within a popula-tion during different eras. (Although menarche does notsignal the onset of puberty,researchers often use the aver-age age of menarche when comparing the timing of pu-berty across different groups or regions.)

1 Main ly A fri can descent

1 Main ly Asiati c descent

1 Native inhabitant s of Australi a(Aborigines), Near East, India,N. Afri ca, and S. Ameri ca

1 Mainly European descent

12.8 13.0-

12.8

13.8

13.1

12.812.5

14.1

12.9

13.3

15.1

12.5

13.0

12.3

14.1

14.6

13.416.5

17.014.9

15.4

15.0

14.9

13.4 14.0-

13.0

15.2

13.0

13.213.2

12.9

13.2

13.0

13.3

14.4 15.2-

13.6 14.0-

12.3 13.2-

13.4

13.0

12.8 12.6

13.2

13.2

14.3

14.213.2

12.8-1.44

12.9

13.2

13.2

13.2

12.5

13.3

13.0

12.7

Figur e 1.7 The average menarcheal age of adolescent girl s varies in di fferent regions of the world. (Adapted from Eveleth &Tanner, 1976)


17/39

of these regions range from about 6 months to about18 months.

Finally, we can examine environmental influences

on the timing of puberty by looking at changes in theaverage age of menarche over the past two centuries.Because nutritional conditions have improved duringthe past 150 years, we would expect to find a decline inthe average age at menarche over time. Thi s is indeedthe case, as can be seen in figure 1.8. Generally, chil -dren have been getting larger and growing to maturitymore rapidly (Eveleth & Tanner, 1990, p. 205). Thispattern, referred to as the secular trend, is attributablenot only to improved nutrition but also to better sani-tation and better control of infectious diseases. In mostEuropean countries, maturation has become earli er byabout three to four months per decade.For example, inNorway 150 years ago,the average age of menarche mayhave been about 17 years. Today, it i s between 12 and13 years. Similar declines have been observed over thesame time period in other industrialized nations and,more recently, in developing countr ies. The seculartrend is less well documented among boys, in part be-


17.0

16.0

15.0

14.0

13.0

12.0

1840 1860 1880 1900 1920 1940 1960 1980

Year of menarche

14.0

13.5

13.0

1950 1960 1970

Ageatm

enarche(yr)

Germ any

Norway

Sweden

Denm ark

Un i ted States

Fin land

Figur e 1.8 The age at menarche has declined considerably over t he past 150 years. This decline is known as the secular trend.(Adapted from Eveleth & Tanner, 1976)

First, consider variations in the age of menarche acrossdifferent regions of the world.Figure 1.7 presents medianmenarcheal ages throughout the world, across regions

that vary considerably in typical dietary intake and healthconditions. As you can see, the average age at menarchegenerally is lower in those countries where individuals areless likely to be malnourished or to suffer from chronicdisease. For example, in Western Europe and in theUni ted States, the median menarcheal age ranges fromabout 12.5 years to 13.5 years. In Africa,however, the me-dian menarcheal age ranges from about 14 years to about17 years.The range is much wider across the African con-tinent because of the much greater variation in environ-mental conditions there.

When we look withina specifi c region, we fi ndthat, almost wi thout exception, gir ls from affl uenthomes reach menarche before economically disad-vantaged gir ls. In compari sons of affluent and pooryoungsters from the Uni ted States,Hong Kong,Tunis,Baghdad, and South Afr ica, for example, differencesin the average menarcheal ages of economically ad-vantaged and disadvantaged youngsters within each


18/39

cause there is no easily measured indicator of puberty,such as menarche, in boys and in part because repro-ductive development is less sensitive to environmentalstimul i among males than females.Although some datasuggest that the secular trend in pubertal maturation

appears to be leveli ng off in most industriali zed na-tions, other studies indicate that the onset of pubertyhas continued to occur earli er, at least among girl s.Today, a significant minority of American girl s showone or more signs of puberty by age 7 (Herman-Giddens et al., 1997), and the average child reports firstfeeling sexually attracted to others at around age 10(McClintock & Herdt, 1996).


THE P SYCHOLOGICAL AND

SOCIAL IMPACT OF P UBERTY

Puberty can affect the adolescents behavior and psycho-logical functioning in a number of ways (Brooks-Gunn,Graber, & Paikoff, 1994). First, pubertys biologicalchanges can have a direct effect on behavior. Increases intestosterone at puberty are directly linked, for example, toan increase in sex drive and sexual activity among adoles-cent boys (Halpern,Udry,& Suchindran,1996). (The im-pact of hormonal change on girls sex drive and sexual ac-tivity is more complicated,as you wil l read in chapter 11.)

Second, the biological changes of puberty causechanges in the adolescents self- image, which in turnmay affect how he or she behaves. For example, a boywho has recently gone through puberty may seek moreprivacy at home when he is dressing or bathing. Hecloses his door more often and is more modest aroundhis parents than he used to be. If they are responsive to

his discomfort, his parents will change their routinesaround the house. Before entering his room, they willknock and wait to see if he is dressedsomething theydid not have to do before.

Finally, biological change at puberty t ransforms theadolescents appearance, which in turn may eli citchanges on how othersreact to the teenager. Thesechanges in reactions may provoke changes in the ado-lescents behavior. An adolescent girl who has recentlymatured physically may find herself suddenly receivingthe attenti on of older boys, who had not previouslypaid her much heed. She may feel nervous about all theextra attention and may be confused about how sheshould respond to it. Moreover, she must now make de-cisions about how much time she wishes to devote todating and how she should behave when out on a date.

Hormonalchanges

Changes inadolescent'sbehavior

Hormonalchanges

Changes inadolescent'sappearance

Changes inadolescent'sself-image


Hormonalchanges

Changes inadolescent'sappearance

Changes inreactions ofothers


Figur e 1.9 The biologicalchanges of puberty can affectthe adolescent 's behavior inat least three ways.

RECAP

There is considerable vari ati on in the timing and tempoof puberty.As a result , a group of adolescents of thesame chronological age wi ll contain youngsters whose

physical matur it y varies considerably. The most impor-tant influence on the timing of maturati on is genetic.But, in addit ion, adolescents who have been well nour-ished and healthy dur ing chi ldhood go through pubert yearl ier than their peers. Because of improvements innut ri ti on and health care, young people mature earl iertoday than they did centuri es ago, a phenomenonknown as the secular tr end.

Food for Thought

Data seem to indi cate that the trendtoward earl ier pubert y has been muchgreater among females than males.

Can you speculate on why thi s might be?


19/39

puberty.One approach is to look at individuals who areat various stages of puberty, either in across-sectionalstudy(i n which groups of individuals are compared atdifferent stages of puberty) or i n a longitudinal study(in which the same individuals are tracked over time asthey move through the stages of puberty). Studies of

this sort examine the immediate impact of puberty onyoung peoples psychological development and socialrelations. Researchers might ask, for example, whetheryoungsters self-esteem is higher or lower dur ing pu-berty than before or after.

A second approach compares the psychological de-velopment of early and late maturers. The focus ofthese studies is not so much on the absolute impact ofpuberty but on the effects of differential timing of thechanges. Here, a typical questi on might be whetherearly maturers are more popular in the peer group thanlate maturers are.

The Immediate Impact of Puberty

Studies of the psychological and social impact of pu-berty indicate that physical maturati on, regardless ofwhether it occurs early or late, affects the adolescents

Young peoples reactions to the changes brought onby puberty, and others reactions to them, are influencedby the broader social environment, where messagesabout physical attractiveness,sexuali ty,and sexual matu-ration change,often markedly, from era to era.Althoughit i s difficult to imagine an era in which adolescents, es-

pecially girls, did not obsess about their shape, size, andsexual allure, adolescent females preoccupation wi ththeir body is a relatively recent phenomenon, createdlargely by marketers of clothing, undergarments, cos-metics, weight-loss programs, and feminine products(Brumberg, 1997). Contemporary societys views of pu-berty and physical maturation are expressed through tel-evision commercials, newspaper and magazine adver-ti sements, and depictions of young adolescents in filmsand other media. People cannot help but be influencedby these images,and the expectations they associate withpuberty as well as the meaning they give it determine thereactions puberty brings out in them. Consider, for ex-ample,the treatment of menstruation in each of the ad-vertisements on page 000.What sorts of reactions mighteach of the ads foster?

Researchers have generally taken two approaches tostudying the psychological and social consequences of


One sign that at ti tudes toward menstr uati on have changedin the past 50 years is that advert isements for t ampons andsanit ary napkins have become far more expli cit and far myste-rious.As a consequence, today' s adolescent gir ls receive mes-

sages about the meaning of maturat ion that are very dif ferentfrom those of 40 or 50 years ago. Here are two excerpts frommagazine advert isments for sani tary napkinsone from the1950s, the other fr om the 1990s. (KOTEX is a registered trade-mark of Kimberly-Clark Corporation. These advert isementsreprinted by permission. All rights reserved)


20/39


self-image, mood, and relationships with parents. Asyou will read,however, the short- term consequences ofpuberty may be more taxing on the adolescents familythan on the adolescent.

Puberty and Self-Esteem Research suggests that

puberty is a potential stressor with temporary adversepsychological consequences for girls (but not boys),but only when it is coupled with other changes thatnecessitate adjustment (Simmons & Blyth, 1987). In-deed, studi es suggest that the impact of puberty onadolescents psychological functioning is, to a greatextent, shaped by the social context in which pubertytakes place (Brooks-Gunn & Reiter, 1990; Susman,1997). Accordingly, the impact of puberty on mentalhealth varies by gender and across ethnic groups,with girls more adversely affected than boys and withwhite girl s, in particular, at greatest risk for develop-ing a poor body image (Rosenblum & Lewis, 1999;

Siegel, Yancey, Aneshensel, & Schuler, 1999). Giventhe premium placed in contemporary society onthinness, the increase in body dissatisfaction amongwhite girls that takes place at puberty i s, not surpri s-ingly, li nked to specific concerns gir ls have abouttheir hips, thighs, waist, and weight (Rosenblum &Lewis, 1999). Interesti ngly, the way adolescents feelabout their physical appearance when they beginadolescence remains remarkably stable over time, re-gardless of whether their actual att racti venesschanges (Rosenblum & Lewis, 1999).

Adolescent Moodiness Although an adolescentsself-image could be expected to be changed during atime of dramati c physical development, it could alsobe the case that self-esteem or self-image is a reason-ably stable characteri sti c, with long and sturdy rootsreaching back to childhood. For thi s reason, some re-searchers have turned their attention to the impact ofpubert y on more tr ansient states, such as mood. Onereason for this focus is that adolescents are thought tobe moodier, on average, than either children oradults. One study, in which adolescents moods weremoni tored repeatedly by electronic pagers, for exam-ple, showed that adolescents moods fluctuate duri ngthe course of the day more than the moods of adultsdo (Csikszentmihalyi & Larson, 1984) (see figure

1.10).Many adults assume that adolescent moodiness is

directly related to the hormonal changes of puberty(Petersen,1985). Is there any scienti fic evidence that the

hormonal changes of puberty cause adolescents to bemoody or, for that matter, that these hormonal changesaffect the adolescents psychological functioning or be-havior at all?

According to several comprehensive reviews of re-search on hormones and adolescent mood and be-havior, the direct connection between hormones andmood, although apparent, is not very strong(Buchanan, Eccles, & Becker, 1992; Flannery,Torquati, & Lindemeier, 1994). When studi es do finda connection between hormonal changes at pubertyand adolescent mood or behavior, the effects arestrongest earl y in puberty, when the system is being turned on and when hormonal levels are highlyvari able. For example, studies indicate that rapid in-creases in many of the hormones associated with pu-bertysuch as testosterone, estrogen, and variousadrenal androgensespecially when the increasestake place very early in adolescence, may be associ-

ated with increased irr itabil it y, impulsivi ty, aggres-sion ( in boys), and depression ( in gir ls). One inter-pretati on of these findings is that i t i s not so much theabsolute increases in these hormones during pubertybut their rapid fluctuation early in puberty that mayaffect adolescents moods. Once the hormone levelsstabil ize at hi gher levels, later in puberty, their nega-ti ve effects appear to wane (Buchanan et al., 1992).There is also evidence, which is discussed in chapter2, that impor tant changes take place in early adoles-cence in the regions of the brain that play major rolesin the processing of emoti on (Spear, 2000).

Even sti ll, most researchers agree that the impact

of hormonal change on mood and behavior in ado-lescence is greatly influenced by environmental fac-tors (Susman, 1997). An excellent i ll ustration of theway in which hormones and environment interact atpuberty comes from the work of psychologist JeanneBrooks-Gunn and her colleagues (Brooks-Gunn,1987, 1989; Brooks-Gunn, Graber, & Paikoff, 1994;Brooks-Gunn & Warren, 1989), who have been study-ing the development of psychological problems, suchas depression and aggression, in young girls aroundthe time of pubert y. Although rapid increases in hor-mones early in puberty are associated with depressedmood in gir ls, it turns out that stressful li fe events,such as problems in the family, in school, or wi th

fr iends, play a far greater role in the development ofdepression than do hormonal changes. Moreover, asshe and others point out, it i s possible that changes inthe environmentin levels of stress, for i nstance


21/39


moodiness. In one study of adolescents, for example,five distinct patterns of mood change were identified(Bence, 1992) (see table 1.2). One group showed con-siderable fluctuati on in mood over the course of aweek, but members typically were in a positive mood(these youngsters bounced back up to positi ve moodsquickly after being in a bad mood). A second group

was, on average, equall y positi ve as the fi rst butshowed much less mood fluctuation. The third groupwas similar to the second, in that members showedli tt le fluctuation in mood;however, in contrast to thesecond group, the third group was generally in aslightly bad mood. The fourth group, li ke the fi rst,showed considerable fluctuation in mood but wasgenerally in a bad mood (that is, members droppedback down to negative moods quickly after being in apositi ve mood). Finally, the fifth group was composedof youngsters whose mood did not fluctuate greatl ybut who were in an extremely negative mood most ofthe time.

Changes in Sleep Patterns One fascinating find-ing on hormones and behavior in adolescence con-cerns adolescents sleep preferences. Many parentscomplain that their teenage children go to bed toolate in the evening and sleep too late in the morning.It now appears that the emergence of this patterncalled a delayed phase preferenceis directly re-lated to the biological changes of pubert y(Carskadon, Acebo,Richardson, Tate,& Seifer, 1997).Thus, physically mature teenagers who are forced tomaintain a sleep schedule similar to that of prepuber-tal individuals have biological reasons to feel ener-getic when it is time to go to bed and lethargic in the

morning. When allowed to regulate their own sleepschedules (as on weekends), most teenagers wi ll stayup until around 1 A.M. and sleep until about 10 A.M.It is therefore ironic that many school districts ask

affect hormonal activi ty, which in turn may affectadolescents mood.

Interestingly, not only is there li tt le evidence thatadolescents moodiness results from the storm andstress of raging hormones, but there is also researchthat questions the very idea that adolescents are inher-entl y moodier than children. Psychologists Mihaly

Csikszentmihalyi and Reed Larson (1984; Larson &Lampman-Petraitis, 1989) had teenagers carry elec-tronic pagers similar to the ones physicians carry, andthe researchers paged them periodically throughout theday. When the adolescents were paged, they filled outforms noting how they were feeling,what they were do-ing, where they were, and whom they were with. Bylooking at changes in mood across activities and set-tings, the researchers were able to determine the corre-lates of adolescent moodiness.

Their findings suggest that adolescent moodswings parallel their changes in activiti es. Over thecourse of a day, a teenager may shift from elati on to

boredom, back again to happiness, and then to anger.But this shift ing appears to have more to do wi th shiftsin activitieselated when seeing a girlf riend, boredin social studies class, happy when having lunch withfr iends, and angry when assigned extra work at thefast-food restaurantthan with internal, biologicalchanges. More important, compari sons of youngstersbetween the ages of 9 and 15 did not show increases inmoodiness during the transiti on into adolescence. Al-though adolescents may be moodier than adults, it i sprobably because they change activities and contextsmore often than adults do.

How can we reconcile these scientific studies,which provide li tt le support for the notion that ado-

lescents are especially prone to mood swings, with thepopular por tr ayals of teenagers as exceedinglymoody? One suggestion is that there is a great deal ofvariability within the adolescent population in

Source: Bence, 1992.

Pattern Size ofMood Change Rate ofMood Change Typical Mood Intensity ofMood

I Very large Very fast Positive Very high

II Small Average Positive Low

III Small Slow Negative Very lowIV Very large Average Negative High

V Average Slow Very negative High

Table 1.2 Five patterns of adolescent moodiness


22/39


(A) The Week of Katherine Tennison

Negative Positive

Eatin g lunch, talkin g to friends about Malnoti 's pizza

Walki ng home alone, think in g "How I was going to do my homework and rehearse toni ght."

Gettin g ready to leave for rehearsal, worry in g/ With fam il y

Putting th e car i n th e garage, tryi ng to get the steeri ng wheel unl ocked

Reading hi story assignm ent in music room; thi nki ng "whether or not to drop the atomic bomb."In gym , talki ng with fr iend, and listeni ng to teacher

Pract ic ing viol i n in her room/ Alone

Doin g history assignm ent; "think in g about other things"/ Alone

Gettin g ready for school, worryi ng how late she will be/Al one

In Music class, taking notes and listening to the teacher

In English, readin g paper th at was just return ed; "panicki ng"In Orchestra, playing the violi n

Walki ng hom e,"botheri ng Lonn ie and Suzanne"

Watching the n ews; eatin g dinn er wi th sister

Playing viol in solo for Carmen; "the show is terrif ic!"

In music room, reading Hi story; li stenin g to rehearsalIn Ameri can history, listeni ng to lecture on the Korean War

Eatin g dinn er and watchi ng TV wit h sister

Playing a jazz piece on the piano/ Alon e at home

In H istory, talki ng about the beeper with a fr iend; worryi ng about a quizIn th e hall ; talki ng with fr iends about the maltr eatment of the music depart ment by the student newspaper

Walki ng hom e, talki ng to Suzanne

Gettin g ready for Carmen; talki ng on the phon e

Leaving for the show; talking with family; worrying about being late

In church, having di scussion with youth cl ass; "daydreamin g"In church; plannin g act iv i t i es; talk ing with f r iends and relaxing

Sleeping; tryi ng to get homework done/ Alon e

Gettin g ready for school; worry in g about being on ti me

In Music Literature, listenin g to a Charl es Ives recording; "daydreamin g about what I had done the day before"Eatin g lunch i n the cafeteria; daydreami ng and talkin g;"What a gorgeous day! 80 fi nal ly ! Everyon e is spaced."

2:57

Mon day 12:44 P.M.

Wednesday 7:32 A.M .

6:42 P.M.

10:28

10:58

5:24 P.M.

7:04

10:25

12:16 P.M. 1:35

3:00

6:02

8:58

9:38

5:58 P.M.

7:02

11:32

3:15 P.M.

4:58

7:00

Tuesday 8:42 A.M .

Thu rsday 8:50 A.M.

Fri day 9:06 A.M.

Sun day 9:45 A.M.

Mon day 7:20 A.M.

10:15

7:25 P.M.

10:32

12:40 P.M.

Mood ( raw score)

24 16 8 0 8 16 24What she was doin g and thin ki ng about

Figur e 1.10 Fluctuat ions in two adolescents moods over the course of week. (Csikszentmihalyi & Larson,1984)


23/39


Negati ve Posi t i ve

2:52

Mon day 12:45 P.M.

Wednesday 7:30 A.M .

10:25

11:00

12:35 P.M.

10:30

12:15 P.M.

1:30 3:00

6:00

8:55

12:30 P.M.

11:30

12:15 P.M.

3:15

Tuesday 8:44 A.M .

Thu rsday 8:50 A.M.

Fri day 9:05 A.M.

Sun day 1:20 P.M.

Monday 7:20 A.M.

6:15

8:30

10:30

6:40

8:30

2:05

5:15

7:05

4:25

2:10 P.M.

6:00

7:05

10:00

1:20

4:55

6:45

8:15

10:20

Mood ( raw score)

24 16 8 0 8 16 24What he was doin g and thi nk in g about

(B) The Week of Gregory Stone

Walki ng down the hall at school with a fr iend

Walki ng to work wi th a gir lOn a dinn er break at work, headin g for Arby's; "I 'm hungry "

At work, r earran ging women's personal products; "I was hopin g I wouldn't get beeped right now"

Lyin g in bed, daydreami ng about the Prom; li stenin g to music

In English Li t. discussing Lord Tennyson's "Memoriam"; thi nki ng about "the Creeds in th e poem"

In Chemi stry, watchi ng movie; complain in g to teacher th at the sound is too loud; "This movie is terr ibl e"Outside at school; "rappin g to a fri end"

In Sociology, listeni ng to teacher talk about "livi ng together"

At work, cleaning shelves; just dropped wristwatch

Getti ng off work; rushin g to catch the el train ; "I want to get hom e and eat"

In ki tchen, pulli ng toast from the toaster, talki ng to sister

In Chemi stry, takin g notes on the reactions of hydrogen and oxygen

"Rapping to fri ends" on the school mall ; admi ri ng graffit i

In typi ng class; typi ng a letter; being bored

Walki ng to work alone; starin g at a squir rel

At work; pri cing and stocking Q-tips

At work; maki ng room for n ew products; listening to the radio

Doin g homework i n room ; listenin g to new wave music

In English Li t. studyi ng the poem "Prospice"

In th e cafeteri a with fri ends; looking at girls with blon d hair

In Sociology, daydreamin g and wonderin g "Should I call my gir l f r i end tonight?"

Eating dinner and talking with brother; watching TV

In ni ght school English class; "Ponderin g if I would li ke to be an author of chi ldren's books"

Talkin g to brother in bedroom; li stenin g to stereo

Walki ng to Gym class; "Will thi s be another Drugland weekend?"

In Chemi stry ; "Spacing off"

At home watching "Bozo's Circus," heating a sandwich for lunchIn Sociology, handi ng i n a t est

Taking out the garbage at work; "Checking out a girl"

At work, bri ngin g stock out from the back room

Moppin g the bathroom at work; thin kin g about "a lecture on th e E.R.A. I atten ded a few weeks ago"

At girl fri end's, watchin g a game of backgamm on; dri nki ng beer

At gir l f r iend's, takin g a hit of f a join t ; talk i ng and remi ni scin g; "We're wasted!"

Startin g on a bike ri de; talkin g with a girl

At home, watching a "60 Minutes" presentation on Ar thu r Ashe; "I never kn ew he was black"

In bedroom, resting and l istening to m usic; "Should I call my gir l f r i end?"

Talkin g to mother i n ki tchen; "Should I eat pi zza with m y mother toni ght?"

In Chemistry; daydreamin g about the gir l and the bike ri de


24/39

adolescents to report to school even earlierthanyounger children, since thi s demand clearl y conflictswith the natural sleep preferences of adolescents. In-deed, one study found that adolescents were leastalert between the hours of 8 and 9 A.M. (when mostschools start) and were most alert after 3 P.M., whenthe school day is over (Al len & M irabell , 1990).

Although individuals preferred bedtime gets later asthey move from childhood into adolescence, theamount of sleep they need each night remains constant,at around nine hours. Yet in one study of more than3,000 Rhode Island high school students, it was foundthat only one-fifth of the students got at least eighthours of sleep on an average school ni ght and thatnearly half got seven hours or less (Wolfson &Carskadon, 1998). There is now a clear consensusamong scientists that most American teenagers are notgetting enough sleep,and that inadequate sleep is asso-ciated in adolescence with poorer mental health (moredepression and anxiety) and lowered school perfor-mance. In the Rhode Island study, for example, the stu-

dents who were earning grades ofCor lower were goingto bed 40 minutes later and sleeping about 25 minutesless each night than their classmates whose grade-pointaverages were Bor better. The students with poorer


grades also reported staying up considerably later onweekends than they did on school nights.Despite manyadolescents belief that catching up on their sleep onweekends makes up for sleep deprivation during theweek, research indicates that having markedly di fferentbedtimes on weekend versus weekday evenings con-tributes to further sleep-related problems (Wolfson &Carskadon, 1998).

Puberty and Family Relationships Research i ntothe impact of pubert y on family relati onships haspointed to a fairly consistent patternnamely, thatpuberty appears to increase conflict and distance be-tween parents and children. The distancing effect ofpuberty on adolescent-parent relationships is not asstrong in single-parent homes (Anderson,Hethering-ton, & Clingempeel, 1989) and not as consistently ob-served in ethnic minori ty famil ies, however (Molina& Chassin, 1996; Sagrestano, McCormick, Paikoff, &Holmbeck, 1999). Among white famili es, though,

several studies show that, as youngsters mature fromchildhood toward the middle of puberty, distance be-tween them and their parents increases, and conflictintensifies, especiall y between the adolescent and his

Studies indicate that parent-adolescent conflict may increase during puberty. (Stewart Cohen/Tony Stone Images)


25/39

or her mother (Laursen, Coy, & Collins, 1998; Paikoff& Brooks-Gunn, 1991). The change that takes place isreflected in an increase in negati ves (e.g., conflict,complaints, anger) and, to a lesser extent, a decreasein posit ives (e.g., support , smiles, laughter) (e.g.,

Flannery et al., 1994; Holmbeck & Hil l, 1991). Al-though negative interchanges may diminish after theadolescent growth spurt, adolescents and their par-ents do not immediately become as close as they werebefore the adolescents entered puberty. Interestingly,puberty increases distance between children and theirparents in most species of monkeys and apes, andsome writers have suggested that the pattern seen inhuman adolescents has some evolutionary basis(Steinberg,1987a).

Because this connection between pubertal matu-ration and parent-child distance is not affected by theage at which the adolescent goes through pubertyin other words, the pattern i s seen among early as well

as late maturers

it suggests that something aboutpuberty in particular transforms the parent-childbond. To date, it is unknown whether this effect re-sult s from the hormonal changes of pubert y, fromchanges in the adolescents physical appearance, orfrom changes in adolescent psychological function-ing, which in turn affect family relationships. More-over, because few studies of famil y relati onships atpuberty have examined mul tiple aspects of adoles-cent development simultaneously, it is difficult to saywhether the patterns of change in family relati on-ships that many studies have found do, in fact, resultfrom puberty and not from another change taking

place at the same time in the adolescent or in the par-ent (Paikoff & Brooks-Gunn, 1991).Whatever underlying mechanism that is involved,

one interpretation of these studi es is that develop-ments occurring around the time of pubert y can up-set the interpersonal balances established duringchildhood, causing temporary peri ods of disruptionin the family system. Dur ing a sons or daughterschildhood, famil ies develop patterns of relati onshipsthat are comfor table and workable,but they may findthat puberty disrupts the patterns to which they havegrown accustomed. They have developed a certainway of discussing things and a certain way of includ-ing the chil dren in discussions. However, as the chil-

dren go through puberty, they may want to be treatedmore like adults and may want to have greater say infamily decisions. Consequently, famil ies may experi -ence a temporary period of conflict or tension when


sons and daughters enter early adolescence. It maytake some time for the individual and the family toachieve a new equilibrium that takes into account thechanges brought on by puberty.

Puberty may have an effect on relationships in the

peer group, too. One study of adolescents social net-worksthe people they are most likely to see andspend time withfound that adolescents who werephysically mature were less likely than their less devel-oped peers to name adults as people who were impor-tant to them, and they were more likely to name otheradolescents (Garbari no, Burston, Raber, Russell , &Crouter, 1978).This finding suggests that pubertal mat-urati on may influence adolescents interests and ener-gies toward the peer group. Boys and girls who arephysically mature are more likely than less mature age-mates to be involved in cross-sex activi ties, such as hav-ing a boyfriend or girlfriend and going out on dates(Crockett & Dorn, 1987), although this depends on the

social norm of the adolescents peer group and the pre-vailing expectations about the age at which teenagersshould begin dating (Dornbush et al., 1981; Gargiulo,Attie, Brooks-Gunn,& Warren, 1987).

The Impact of Specific Puberta l Events

Several studies have focused specifically on adolescentsattitudes toward and reactions to particular events atpuberty, such as girls reactions to menarche or breastdevelopment, and boys reactions to their first ejacula-tion. In general, most adolescents react positively to thebiological changes associated with puberty, especially

those associated with the development of secondary sexcharacteristi cs. One study of adolescent girls att itudestowards breast development, for example, found thatmost of the girls greeted this change positi vely (Brooks-Gunn,Newman,Holderness, & Warren, 1994).

Girls reactions to menarche are more varied, how-ever, in part because the onset of menstruation is notjust one of a series of physiological events during pu-berty, but is also a sociocultural event . . . imbued withspecial meaning (Brooks-Gunn & Ruble, 1979, p. 1).Cultural beliefs concerning menarche and the specificinformation that a young woman receives from parents,teachers, fr iends, and health practi ti oners all influencehow she greets and experiences menarche (Brooks-

Gunn & Ruble,1982).Adolescent girls att itudes toward menarche are less

negative today than they appear to have been in the past(Grief & Ulman,1982; Ruble & Brooks-Gunn,1982), a


26/39

change that may be att ributable to the more open pres-entation of information about menstruation in schoolsand in the media in recent years (Merskin, 1999). Ingeneral, among todays adolescent gir ls, menarche istypically accompanied by gains in social maturity,

peer prestige, and self-esteem

as well as by height-ened self-consciousness (Brooks-Gunn & Reiter,1990). Nevertheless, many young women have devel-oped a negative image of menstruation before reach-ing adolescence, and they enter puberty with ambiva-lent attitudes about menarchea mixture ofexcitement and fear (Moore, 1995; Ruble & Brooks-Gunn, 1982).

Interesti ngly, one set of studi es indicates that astrong negative bias toward menstruation beforemenarche may actually be associated with greatermenstrual discomfor t. Menstrual symptoms are re-ported to be more severe among women who expectmenstruation to be uncomfortable, among gir lswhose mothers lead them to believe that menstrua-tion will be an unpleasant or uncomfortable experi-ence, and in cultures that label menstruation as animportant event. In addition, gir ls who experi encemenarche early, relati ve to their peers, or who areotherwise unprepared for puberty report more nega-ti ve reactions to the event (Koff & Rierdan, 1996;Rierdan, Kobb, & Stubbs, 1989).

Far less is known about boys reactions to their fi rstejaculati on, an experience that we might consider anal-ogous to menarche in gir ls.Although most boys are notvery well prepared for this event by their parents orother adults, first ejaculation does not appear to cause

undue anxiety, embarrassment, or fear. It is interestingto note,however, that, in contrast to gir ls,who generallytell their mothers shortly after they have begun men-struating and tell their girlfri ends soon thereafter, boys,at least in the Uni ted States, do not discuss their firstejaculation with either parents or friends (Gaddis &Brooks-Gunn, 1985; Stein & Reiser, 1994). In other cul-tures, the event may be experienced somewhat di ffer-ently.For example,one study of first ejaculation amongadolescent boys in Nigeria found not only that the boyswere not upset by the event but also that they told theirfr iends about the experience very soon after it occurred(Adegoke,1993). Cultural dif ferences in boys responsesto their first ejaculation are likely related to differencesin how different cultures view masturbation. As is thecase with gir ls and menarche, boys reactions to theirfirst ejaculation are more positive when they have beenprepared for the event (Stein & Reiser, 1994).

44

The Impact of Earl y or L ate Maturation

Adolescents who mature relatively early or relatively latestand apart from their peers physically and may,as a con-sequence, elicit different sorts of reactions and expecta-tions from those around them.Moreover, individual ado-lescents may be all too aware of whether they are early orlate relative to their agemates, and their feelings aboutthemselves are likely to be influenced by their compar-

isons. Indeed,adolescentsperceptionsof whether they arean early or a late maturer are more strongly related totheir feelings about their physical maturation thanwhether they actually are early or late (Dubas, Graber, &Petersen, 1991), and adolescents behavior is related tohow old they feel, not simply to how physically maturethey actually are (Galambos, Kolaric, Sears, & Maggs,1999). Nevertheless, early and late maturers are oftentreated differently by others and view themselves differ-ently; as a result , they may behave differently. As we willsee, however, early and late maturation have differentconsequences in the immediate present and the long run;different consequences in different contexts; and, mostimportant,different consequences for boys and girls.

Early Versus Late Maturation Among Boys Thefirst studies to compare early- and late-maturing boyssuggested that it is an advantage to mature earlier than

RECAP

Although pubert y may cause temporary disrupti on inthe adolescent 's social relat ionships and changes in sleeppatterns, research has not shown that puberty is inher-

ently str essful or associated wi th dramat ic changes inmood or behavior. Pubert y may be associated wi th i n-creases in negati ve moods, but only duri ng the very earl ystages of hormonal change, when hormone levels arefluctuating widely. More important than puberty itself ishow pubert y is viewed withi n the context in which theadolescent matures, as well as the extent to which theadolescent has been prepared psychologically for thebiological changes of the era.

Food for Thought

Examine the two mood diagrams thatwere presented in figure 1.10. Can you

draw any generalizations about the roleof context in mood fluctuation?

Part I The Fundamental Changes of Adolescence


27/39

for late-maturi ng boys,despite their initi ally lower pop-ulari ty with peers.Although early and late maturers ex-hibit similar psychological profiles before they enter

adolescence, during the time of pubertal onset, aswell as one year later, late maturers show significantlyhigher ratings on measures of intellectual curiosity, ex-ploratory behavior, and social ini tiative. Interestingly,early maturers experience more frequent and moreintense temper tantrums during puberty (Livson &Peskin, 1980).

Why might this be?One explanation is that late ma-turers have the advantage of a longer preadolescent pe-ri od,giving them more time to prepare psychologicallyfor the onset of puberty (Peskin, 1967). This prepara-tion may be important i f rapid increases in hormonesat puberty provoke changes in mood. Many theoristsbelieve that the middle childhood and preadolescent

years are extremely important periods for the develop-ment of coping skil lsskills that prove valuable duringadolescence and adulthood. Although puberty by nomeans marks the end of the growth of coping abil it ies,

ones peers. Drawing on data collected as part of theOakland Growth Study (a lon

chapter 1 biological transitions

Documents