DIVERSITY

Gender Similarities inMathematics and ScienceJanet Shibley Hyde'· and Marcia C.linn2

Boys and girls have similar psychological traits and cognitive abilities; thus, a focus on factors otherthan gender is needed to help girls persist in mathematical and scientific career tracks.

The role of gender in mathematics andscience education is hotly contested (1).Some advocate single-sex schooling as

a way to let girls' talents blossom, freed fromboys' domination in the classroom and

from sexual harass-ment by boys (2, 3).

Others emphasizegender differences

in learning styles,citing evidence that

girls perform best under cooperative learningconditions and boys perform best in competitivelearning environments (4). These argumentsrest on the assumption that pSYChological gen-der differences are large and exist in numerousQQmains. Should gender be the major factor {;;'deciding which school a child attends or whichcurriculum a child receives? The GenderSimilarities Hypothesis (5) provides an alterna-

.rive view, stating instead that males and femalesare very similar on most, but not all, psycholog-ical variables.

Enhanced online at

'NWW sciencemaq org/cgl/come nt/I u11/314/5 799/,99

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Evidence for Gender SimilaritiesA review of meta-analyses of research onpsychological gender differences identified46 reports, addressing a variety of psycho-logical characteristics, including mathemati-cal, verbal, and spatial abilities; aggression:leadership effectiveness; self-esteem; andcomputer use (5). These research synthesessummarize more than 5000 individual stud-ies, based on the testing of approximately 7million people. The findings are representedon a common scale based on the standarddeviation. The magnitude of each gender dif-fercnce was measured using the d statistic(6). d= (MM -MF)!sw' where MM is the meanscore for males, MF is the mean score forfemales, and Sw is the pooled within-sex stan-dard deviation. The d statistic measures the

'Department of Psychology, University of Wisconsin.Madison. WI 53706, USA. lEducation in Mathematics,SCIence, and Technology, University 01California. Berkeley,CA94720, USA.

'To whom correspondence should be addressed. E·mail:jshyde@wisc.edu

distance between maleand female means, instandard deviationunits. In each individ-ual meta-analysis, thevalues of d from multi-ple investigations ofthe same outcome wereweighted by samplesize and combined.

A total of 124 syn-thesized effect sizesresulting from meta-analysis were extractedfrom the reports. Fol-lowing convention, dvalues in the range 0.11 to 0.35 were classi-fied as small, 0.36 to 0.65 as moderate. and0.66 to 1.00 as large (6). Values greater than1.0 were categorized as very large and valuesbetween 0 and 0.10 were considered trivial.

Of the effects for gender differences,30% were trivial and an additional 48% weresmall. That is. 78% of the effects for psycho-logical gender differences were smaIl ornear zero. For example, for mathematics

Iproblem-solving. d = 0.08 (7): for leadershipeffectiveness. d = -0.02 (8); and for negotia-tor competitiveness, d = 0.07 (9).

An essential implication of these findingsis that the overlap of distributions for malesand females is substantial for most out-comes. For example, the chart above shows'the distribution of male and female perform-ance for a small effect size of 0.20. Assumingthat performance fits a normal distribution(supporting online material text). for meansthat are 0.20 standard deviations apart (d =0.20). the population show 85.3% overlap.O!}ly 54% of members of.one gender exceed~ ,?Q!hpercentile for the other gender. For d=O. IO. there is 91.3% overlap in the distribu-tions of the two groups. a'2<lJ2~_0t:.those ofone g!!nder ~xceed the 50th percentile for theother. Even for a moderate effect size (d =0.50),60% of members of one gender exceedthe 50th percentile for the other gender.

Most relevant here is the meta-analysis ofresearch on gender differences in mathematics

Effect size of 0.20. When the effect sizebetween twogroups is 0.20, 85.3% of the dis-tributions overlap.

70 85

performance, which wasbased on I00 studies andthe testing of more than 3million people (7). Patternsemerged as a function of theage of test takers and thecognitive level of the test.Girls outperformed boys oncomputation in elementaryschool and middle school (d= -0.20). There was no gen-der difference in highschool. There was no gen-~f[e;;nce in deeperunderstandin!L9LJ1lathe-rnati.cal concepts_at any age.

For complex problem solving, a skill that ishighly relevant for science, technology, engi-neering, and mathematics careers, there was nogender difference in elementary or middleschool; a small difference favoring boysemerged in high school (d = 0.29). Consistentwith these findings of gender similarities inmathematics performance, in 200 I womenearned 48% of the bachelor's degrees in mathe-matics in the United States (/0), demonstratingthat substantial numbers of women do have theability to engage mathematics successfully atthe advanced levels required of a mathematicsmajor.

A few exceptions to the pattern of gendersimilarities were identified in the review ofmeta-analyses. Most relevant to educational

• settings are the gender differences in activitylevel and physical aggressiQD., with effect sizesfor aggression ranging between 0.40 and 0.60(males more aggressive) across several meta-analyses (11-/4). Males display a higher activ-ity level than females, d=0.49 (/5). It is widelybelieved that there are substantial gender differ-ences in interests in fields such as psychologycompared with physics, although ~ found no 7ru£..ta-analysis of this research literature. '

100Scores

115 130

Gender Similarities in ScienceThe National Assessment of EducationalProgress (NAEP), the Nation's Report Card.tests thousands of students across the UnitedStates on achievement in mathematics and

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science. The conclusions from 2005 statedthat males outperformed females at all threegrades tested in science (16). ., 15

Another look at the data leads to a different ~ 10=:conclusion. For fourth-graders, the average '"::;:science score was 152.53 (SD = 32) for boysand 148.66 (SD =30) for girls. That is, the dif-ference is less than 4 points on a scale thatranges from 0 to 300. As NAEP reports, thisgender difference is statistically significant,given the large sample size (roughly 100,000students per grade). However. the effect size,d, for this gender difference is 0.12, reflectinga s~all difference. Increasingly large samples only 16% in physical science and 17% in engi-can detect increasingly small differences, but neering (20). Too often, small differences in Referencesand Notesan assessment of the effect size, d, gives a performance in the NAEP and other studies 1. S. Ceraulo,j. Chern. Edue. 76, 615 (1999).

2. J. l. Streitmatter, For Girls Only: Making a Case formore accurate reflection of the importance of receive extensive publicity, reinforcing subtle, Single-Sex Schooling (SUNY Press, Albany, NY, 1999).

the difference. Emphasis on statistical signifi- persistent, biases (20, 21). Indeed, the magni- 3. M. Warrington, M. Younger, Oxford Rev. Edue. 27,339

cance, while ignoring the magnitude of the Itude of the attitudinal association between sci- (2001).. ... . 4. M. Gunan, A. Ballew, The Boys and Giris Learn Differently

effect, risks exaggerating the importance of ence and males IS large, d =0.72 (22, 23). These .~ Action Guide for Teachers (lossey-Bass, San Francisco,

the differences (J 7). biases can have an impact on decisions about >' CA,2003).The magnitude of the gender gap in sci- admissions, hiring, and promotion J24, 25). f 5. J. S. Hyde, Am. Psych. 60, 5B1 (2005).

ence achievement remains similar from fourth These biases may contribute l.115OOufarbelie s 6. J. Cohen, Statistical Power Analysis for the BehavioralSciences (Erlbaurn, Hillsdale, NJ, ed. 2, 19BB).

to 12th grade. NAEP reports average scores of about same-sex education and learning s es, 7. J. S. Hyde, E. Fennema, S. lamon, Psych. Bull. 107, 139

149.01 for boys (SD =35) and 145.15 for girls and dissuade some individuals from persisting (1990).

(SD = 33) in 12th grade, for an effect size of d in science (26). B. A. H. Eagly, S. Karau, M. Makhijani, Psych. Bull. 117,125(1995).

= 0.11, a small difference that is no larger than For example, advocates of same-sex edu- 9. A. E. Walters, A. Stuhlmacher, l. Meyer, Org. Behav. Hum.

the difference in fourth grade. The NAEP data cation claim advantages for both boys and Dee. Proe. 76, 1 (1998).c· that bovs+zreat acti . 10 National Science Foundation, Women, Minorities, and

pro~v~i~d~e.J.b~e:i!tt~er!..el<.YXJi""d""e•.•=t=girls (2). Some argue " boy,' great activity . ',O.M witb 0""",,",,;. Science and inqineerinqinscience achievement than they do for gen- level and aggressiveness make it difficult for (NSF, Arlington, VA, 2004); available online

d~r differences. girls to learn and participate actively, and at (www.nsf.gov/statistics/wmpd/underdeg.htm).I\ th time.b d 1 that tal 11. J. S. Hyde, Dev. Psych. 20, 722 (1984).c.or-~ e same une, oys nee a c assroom - 12. J. S. Hyde, M. C. linn,The Psychology of Gender: I

Cross-National Comparisons erates their active style. Activity level and Advances Through Meta-Analysis (Johns Hopkins Univ.

Cross-national data provide another way to physical aggression are two exceptions to the Press, Baltimore, MO, 19B6).evaluate the magnitude of gender differences gender similarities ruJe, with effect sizes 13. A. H. Eagly, V. Steffen. Psych. Bull. 100,309 (1986).

14. J. Archer, Rev. Gen. Psychol. 8, 291 (2004).in mathematics and science performance. around 0.50 for each. Yet even a gender differ- 15. W. O. Eaton, l. R. Enns. Psych. Bull. 100, 19 (1986).

Research on fifth-graders' performance on ence of that magnitude means that 40% of 16. The Nation's Report Cardmathematical word problems in the United one group (in this case, girls) score higher (http://nationsreportcard.gov/science_2005).

. 17. l. Wilkinson, Am. Psych. 54, 594 (1999).States, Taiwan, and Japan reveals a slight male than the average for the other group (boys). If 18. M. lummis, H. W. Stevenson, Dev. Psych. 26, 254advantage in each culture. but a larger differ- the idea is to separate children into c1ass- (1990).

ence between culhlres (see chart above) (J 8). rooms for the more active and aggressive and 19. H. W. Stevenson, C Chen, S.-Y. Lee, Science 259, S3

Whereas the effect size for the gender differ- the less active and aggressive, gender is not 20. :l::~~elsman et 01., Science 309,1190 (2005).ence in the United States is d = 0.18, the effect the best indicator. A teacher's rating of activ- 21. J. A. 8argh, T. l. Chartrand, Am. Psych. 54,462 (1999),

size for the difference between U.S. boys and ity level would be far more accurate. 22. B. Nosek, M. Banaji, A. Greenwald, Group Dyn. Theory

Japanese boys is d = 1.42. These cultural dif- The phenomenon of gender similarities Res; Proct., 6 101 (2002).23. B. Nosek, M. Banaji, A. Greenwald,}. Pers. Soe. Psych.

ferences reflect many factors, including differ- has implications for schooling. Emphasis on 83,44 (2002).

ences in curriculum, time spent in homework, gender differences in the popular literature 24. B. Bergmann, In Defense of Affirmative Action

and parents' beliefs in the importance of effort reinforces stereotypes that girls la~.k mathe- (Basic Books, New York, 1996),25. M. C. linn, Educ. Res. 27, 15 (1998).

in school performance (19). Even within the matical and scientific aptitude. However, gen- 26. E. Seymour, N. Hewitt, Talking About Leaving (Westview

United States, the gender difference in mjlthe- der is a poor indicator of whether one will Press, Boulder, (0,1997).matics perform-aDce IS larger in some ethnic major in mathematics or the biological sci- 27. R. H. Tai, C. Q. liu, A V. Maltese, X. Fan, Science 312,

- - 1143 (2006).groups than others. For whites, d = 0.13; ences as an undergraduate. A better predictor 28. This study was funded in part through grants from NSF,whereas for blacks, d = -0.02; for Hispanics, d would be actual mathematics achievement REC 0635444, 0207109, 9980620, and 0233649, and

=0.00; and for AsianAmericans, d= -0.09 (7). scores in middle school or high school (27). A ESI-0242701, 9720384, and 0334199. Any opinions,findings, and conclusions or recommendations expressed

cultural overemphasis on gender differences in this material are those of the authors and do not nec-may mask critical predictive variables and manly reflect the views of the National Science

lead to decision-making that is empirically Foundation.

unsupported. To help teachers succeed, we Supporting Online Materialmay need to address variability in aggression www.sciencemag.org/cgi/contentifuIV314/5799/599/DCland activity level for all learners. To neutralizetraditional stereotypes about girls' lack of

11 EDUCATION FORUM

20I !iI Boys f 1I Girls

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U.S. Taiwan Japan

Cross-national and gender differences in math.Differences in fifth-graders' performance on wordproblems are larger between countries than betweengenders (18). Boys' scores are shown in blue; girls'scores are shown in red.

Implications

I Women earn 46% of the Ph.D.'s in biology but,'> despite evidence for gender similarities, they

~\.. earn only 25% of the Ph.D.'s in physical science~ ~'Ii" and 15% in engineering. Women comprise

('-0 30% of the assistant professors in biology but

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ability and interest in mathematics and sci-ence, we need to increase awareness of gendersimilarities. Such awareness WIll help mentorsa~isers avoid discouraging girls fromentering these fields. Continued monitoringof the relative progress of boys and girls isessential so that neither group falls behind.

Rather than focusing on gender differ-ences, mathematics and science educatorsand researchers could more profitablyexamine ways to increase awareness of thesimilarities in performance and in ability to~ed.

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