handedness for grasping objects and declarative pointing: a longitudinal study

Handedness for GraspingObjects and DeclarativePointing: A Longitudinal Study

ABSTRACT: It is still unclear whether infants become right-handed because oftheir left-hemisphere specialization for language (through gestural communica-tion for instance), whether they speak predominantly with their left hemispherebecause of this hemisphere’s superiority in controlling sequential actions whichfirst results in right-handedness, or whether the two lateralization processes de-velop independently. To tackle this question, we followed 26 human infantsfrom 8 to 20 months to evaluate the temporal relationship between the emergenceof hand preference for grasping objects and for declarative pointing (communica-tive gesture). Our results show that when grasping and pointing are comparedin similar conditions, with objects presented in several spatial positions, thetendency to use the right hand is significantly larger for pointing than for grasp-ing, and both hand preferences are loosely correlated. This suggests that, atleast at the age studied here, hand preferences for grasping and for declarativepointing develop relatively independently. � 2011 Wiley Periodicals, Inc. DevPsychobiol

Keywords: handedness; grasping; pointing; development

INTRODUCTION

Given the fact that across all human societies for which

the question has been studied, almost 90%

of individuals have a preference for using their left-

hemisphere-controlled right hand, and over 90% of

them show asymmetrical language representation in

favor of the left hemisphere, the question of a possible

relationship between the emergence of these two asym-

metries has long been and is still largely debated

(Corballis, 2003, 2009). Did humans start to speak pre-

dominantly with their left hemisphere because of their

right-handedness? Alternately, did they predominantly

use their right hand after developing linguistic or

prelinguistic skills that are mainly controlled by the left

hemisphere and may have involved the hands? Of

course, other possibilities are that the emergence of

language lateralization and manual asymmetries could

be either unrelated or very indirectly related.

At a different scale, it is still unclear whether infants

become right-handed because of their left-hemisphere

specialization for language (through gestural communi-

cation for instance), whether they speak predominantly

with their left hemisphere because of this hemisphere’s

capacity for processing sequential events with high res-

olution, which would become evident in manipulation

prior to language, or whether the two lateralization pro-

cesses are independent. While from an evolutionary

perspective, the possibility of a gestural origin for

language (as opposed to a vocal origin) is still hotly

debated (Arbib, 2005, 2008; MacNeilage, 1998; Vauclair,

2004), from a developmental point of view there is

some consensus that communicative manual gestures

are related to later verbal language development

(Iverson & Goldin-Meadow, 2005; Rowe & Goldin-

Meadow, 2009a; Tomasello, Carpenter, & Liszkowski,

2007). The goal of the current study was to follow

Developmental Psychobiology

Anne-Yvonne Jacquet

Rana Esseily

Delphine Rider

Jacqueline Fagard

Laboratoire Psychologie de la PerceptionUniversite Paris Descartes

CNRS UMR 815845 rue des Sts Peres75006 Paris, France

E-mail: [email protected]

Received 28 October 2010; Accepted 3 May 2011Correspondence to: J. FagardContract grant sponsor: CNRS (ANR Programme)Contract grant numbers: Contract no. 08-3_311472 ANR-08-

BLAN-011_01Published online in Wiley Online Library

(wileyonlinelibrary.com). DOI 10.1002/dev.20572

� 2011 Wiley Periodicals, Inc.

the development of hand preference in human infants

when they start using their hands either to grasp and

manipulate objects or to communicate with adults. The

question posed concerns the temporal relationship be-

tween the emergence of hand preference for grasping

objects and for communicative gesture. In other words,

which of the two, if either, influences the development

of the other?

Infants are first observed to reach for objects around

3 months of age (Hofsten, 1979; Thelen, 1993; White,

Castle, & Held, 1964), and by 5–6 months of age

infants are skilful at reaching for and grasping objects

(Hofsten, 1983). Already in utero—and thus before be-

ing able to grasp objects voluntarily—infants use the

right hand more than the left, for instance for thumb

sucking or for spontaneous movements (Hepper,

McCartney, & Shannon, 1998; McCartney & Hepper,

1999). In addition, hand preference for thumb sucking

in utero or for spontaneous movements at birth are

good predictor of future handedness (Hepper, Wells, &

Lynch, 2005; Michel, 1984). However, despite these

early precursor signs of hand preference, there is some

disagreement about when handedness can be consid-

ered as established: whether it is during the first year of

life, as soon as grasping and manipulating gradually

emerges, or not before the age of three, or even later

(Connolly & Elliott, 1972; Provins, 1997). Although it

is becoming more widely recognized that hand prefer-

ence for grasping emerges during the first year of life

(Kotwica, Ferre, & Michel, 2008; Michel, Tyler, Ferre,

& Sheu, 2006), some researchers have described huge

fluctuations in the pattern of handedness during this pe-

riod of life (Corbetta & Thelen, 1999; Fagard, 1998;

Ferre, Babik, & Michel, 2010).

Infants start using their hands for communicative

gestures later than for grasping objects, but before they

can speak (Butterworth & Morissette, 1996). Early use

of gestures predicts language learning (Rowe &

Goldin-Meadow, 2009b). Some of these gestures in-

volve both hands, such as stretching out arms toward

the mother, while others are more often unimanual, like

pointing at something. Pointing’s communicative func-

tion and pre-linguistic nature are supported by the facts

that infants can point in reference to absent entities,

and that they do not point to objects when nobody

can see them. In addition, pointing often accompanies

spoken words in the early phases of language (Capirci,

Iverson, Pizzuto, & Volterra, 1996; see Capirci &

Volterra, 2008, for a review).

Two kinds of pointing are usually distinguished: im-

perative pointing, by which infants use adults to obtain

out-of-reach objects (sometimes called ‘‘interrogative’’

pointing, Southgate, van Maanen, & Csibra, 2007) and

declarative pointing, by which infants use objects to

attract adults’ attention (Franco & Butterworth, 1996;

Liszkowski, Carpenter, Henning, Striano, & Tomasello,

2004; Cochet & Vauclair, 2010a). Infants’ hand move-

ments during proto-conversation with the mother can

be observed very early, during the first months of life

(Trevarthen, 1996). True declarative pointing can be oc-

casionally observed before the end of the first year, of-

ten with the whole hand, but declarative pointing

with the index finger clearly emerges during the second

year of life and becomes quite frequent at 14 months

(Capirci & Volterra, 2008; Franco & Butterworth,

1996; Iverson, Capirci, & Caselli, 1994). Pointing

has been shown to be mostly right-handed (Franco &

Butterworth, 1996) and communicative gestures in gen-

eral to be more right-biased than object grasping (Bates

& Dick, 2002). However, since handedness for grasping

objects fluctuates at the time of the emergence of

grasping, it would be useful to see whether or not the

choice of a hand for pointing is more stable, and what

influence it has on hand choice for grasping, if any.

Relationships between the two kinds of laterality

(object-related action and gestural communication)

have been the object of two recent studies. In one study

(Vauclair & Imbault, 2009), the same children were

compared at three different ages representing steps in

language development. The authors found that children

who demonstrated a preference for either right or left

hand use in grasping pointed predominantly with the

right hand. In another study, 14-month-old infants were

compared for handedness for grasping objects and

pointing, as well as language development (Esseily,

Jacquet, & Fagard, in press). The authors found no

strong relationship between the hand used for grasping

and the hand used for pointing and a stronger right bias

for pointing than for grasping. However, in none of

these studies were pointing and grasping studied in the

way infants usually grasp and point, namely throughout

space. In ecological conditions, infants grasp the

objects around them, and they point to wherever in

space something interesting happens. Spatial param-

eters are known to influence hand choice. As concerns

grasping, it has been shown in adults and children that

the stronger the hand preference, the further into the

contralateral hemifield individuals will use their pre-

ferred hand (Calvert & Bishop, 1998; Leconte &

Fagard, 2004). To test the effect of spatial parameters

on hand choice, Bishop and colleagues developed a

quantifying hand preference test (QHP) in which

objects to be grasped (cards) are presented in a half-

circle around the subject, who is asked to pick up one

of the cards named by its category and to place it in

front of him/her (Bishop, Ross, Daniels, & Bright,

1996). Given that reaching to a side-presented object

with the contralateral hand is biomechanically much

2 Jacquet et al. Developmental Psychobiology

more difficult than with the ipsilateral hand, the left-

ward limit of the infant’s use of his right hand is a

good index of the strength of hand preference for right

handers (and vice versa for left-handers). To our knowl-

edge, the QHP has never been used with infants to test

object-related hand preference.

In order to compare the order of emergence of hand-

edness for object-related action and for gestural com-

munication, and their possible interaction, we tested

infants when reaching to grasp an object situated at one

of several possible places around him/her (QHP) and

when pointing to a puppet shown far away also at one

of several positions around him/her, in a longitudinal

design. We decided to use declarative pointing to a

faraway object in our comparison between handedness

for communicative gesture and for grasping objects

because, in contrast to imperative pointing, declarative

pointing is not expected to be influenced by the inten-

tion to grasp the coveted object.

METHODS

Participants

Thirty-one families out of 300 on a local list of families who

were contacted participated in the longitudinal study. They

agreed to bring their infants to the laboratory at the ages of

8, 11, 14, 17, and 20 months (more or less 1 week). Due to

moving, new pregnancy of the mother or other family events,

five families dropped out of the study before its end. Four

infants who missed one of the five sessions were kept in the

study, and 22 infants were seen for all five sessions. Thus,

most of the results bear on 26 infants, while some of the anal-

yses with repeated measures were carried out only on the 22

infants who did not miss one session. Parental consent was

granted before observing the infants.

Procedure and Materials

Tests of Handedness. All children were given two tests of

handedness for grasping objects, a classical baby test with

objects presented in the middle (Esseily et al., in press;

Fagard & Lockman, 2005; Sacco, Moutard, & Fagard, 2006),

and an adaptation of the QHP test (Bishop et al., 1996). They

also received a test of handedness for pointing.

Handedness for Grasping. The baby handedness test

(BbHtest) comprises five items to test simple grasping and

two items to test precision grasping. Objects for testing sim-

ple grasping were small baby toys: three Playmobil1 figur-

ines, one hand-shake toy (maracas), and a teether. For

precision grasping, one task consisted in taking a very thin

red tube (6 mm in diameter) inserted in a slightly shorter

transparent tube from which only the top protruded and the

other task consisted in grasping a small horse inserted in a

container that was 30 mm in height. To favor unimanual

grasping, these two objects were presented so that the infants

could not grasp the container, but only the object inside. The

baby handedness test thus comprised seven items in total. All

objects were presented within reaching distance of the infant

at a midline position.

To measure hand preference for grasping in different posi-

tions in space in a way comparable to pointing, we adapted

the QHP test to infants. In accordance with the original set-up

used by Bishop (Calvert & Bishop, 1998), a toy (4 cm in

width) was placed at one of seven positions on a half-circle at

a distance within reach for the infant (Fig. 1). One position

was in front of the infant, three were to the right and three to

the left, each separated by 308. We made sure that each posi-

tion was reachable by the opposite hand. At the first session

(8 months), infants underwent two series of trial, that is, they

were presented with an object twice at each of the seven posi-

tions. Since the results of the two series were highly correlat-

ed, and given the long duration of testing sessions when a

pointing evaluation was included in the protocol, starting at

11 months, we decided to give only one series per session.

Analyses of the 8-month-old bear on the first series only.

Handedness for Pointing. To evaluate handedness in point-

ing, we presented puppets through holes made in a white

sheet lining the wall facing the infant, in a set-up inspired by

Liszkowski (2005) (Fig. 2). We chose to present the puppets

far enough away that pointing to them could not be part of a

reaching movement. Given the size of our experimental room,

we could not have more than five different positions with

enough distance between them to be sure of which position

the infant was pointing toward. The white sheet was

2 m � 1.80 m, and the five holes were 48 cm apart, with an

angle of about 208 between adjacent holes. We presented the

five puppets to the infants (16 cm in width), one at each of

five possible positions, in a randomized order. Infants were

seated at a distance of 2 m from the screen, between a parent

and an observer who encouraged them to indicate the puppet

when they did not point spontaneously. It is relatively difficult

to elicit pointing in an experimental situation. Often even

infants who point spontaneously do not do so in an experi-

mental situation. Thus, we decided to test only once at each

position, because in a cross-sectional study (Esseily et al.,

FIGURE 1 Set-up to evaluate handedness for grasping on

the QHP test.

Developmental Psychobiology Handedness for Grasping and Pointing 3

in press), the handedness seen at the first presentation was

well correlated with handedness at the following two presen-

tations. If an infant did not point on some presentations, the

presentation was repeated, up to three times, until there had

been one pointing for each presentation. In most cases,

infants used a single finger extension, but in some cases they

used the whole hand to point toward the puppet. Pointing was

considered as communicative as long as the hand was palm

down or vertical but not palm up, and there was no sign of

begging from the infant (vocalizations or other body language

indicating a desire to get the puppet). We made it clear from

the beginning that the puppets would stay behind the curtains

and not be given to the infants.

The BbHtest was always given first, since it is the only

handedness test with presentations restricted to the middle po-

sition, and it was important for the infants not to have been

drawn into using their non-preferred hand before this test.

The order of presentation was less important for the QHP test

and the pointing task, since both can trigger the use of either

hand. The QHP test was generally given before the pointing

test because it was presented on the same table as the

BbHtest.

All infants were comfortably seated during the whole ses-

sion. Most of the infants were seated on a high chair in front

of a table for the grasping tests. The infants stayed on the

same chair for the pointing test, but the table was removed,

revealing the panel used for this test. A few infants refused to

sit on the high chair, especially during the first sessions, so

they performed the whole session on the parent’s lap in front

of the table. At 20 months, infants were given a small chair

in front of a lower table to be more comfortable. In all cases,

we were particularly careful to avoid any source of

asymmetry.

Additional Evaluations. In addition, infants were tested for

language development using the short version of the French

adaptation of the MacArthur language test (Bovet et al.,

2005). With the help of an experimenter, the parents filled out

the form, a list of 81 words, among which they mark off each

word that their infant produces and/or understands, at the be-

ginning of each session. Two variables were considered: the

number of words understood and the number of words pro-

duced. The parents were also asked if they wrote with their

right or left hand.

Data Collection and Coding

All trials were videotaped. From the videotape recordings,

observers scored, the hand infants grasped the object with

(BbHtest and QHP), whether they produced pointing, and if

so with which hand (pointing test). Inter-rater agreement,

based on two independent observers scoring 25% of the sam-

ple, averaged 99% perfect agreement for grasping, and 92%

perfect agreement for pointing.

Analyses

To assess handedness on the three tests, we calculated a hand-

edness index (HI) using the classical formula [RH � LH/

RH þ LH] (Coryell, 1985; Corbetta & Thelen, 1999). Thus,

for the BbHtest and for the QHP test, HIb and HIqhp

test ¼ [RH grasps � LH grasps/(RH grasps þ Lh grasps þbimanual grasps)]. For the pointing task, HIp ¼ [RH

points � LH points/(RH points þ Lh points þ bimanual

points)]. From the HIs, the individuals were characterized

as right-handers (HI � 0.50), left-handers (HI � �0.50) or

non-lateralized (HI between �0.50 and 0.50).

RESULTS

Handedness for Grasping

BbHtest. The mean HI calculated on the BbHtest

(HIb) was positive at each session, which means that,

as a group, infants used their right hand more than the

left in all sessions (Fig. 3). The mean HIb tended to

increase with age from 8 to 20 months. However, an

ANOVA on the mean HIb with session (�5) as a

repeated measure on the 22 infants who did not miss

a session showed no significant effect for session

(F(4,84) ¼ 1.9, p ¼ 0.10). We thus decided to calcu-

late a mean HIb across all sessions for a global evalua-

tion of infants’ handedness on the BbHtest. The mean

HIb across all sessions was 0.37 (�0.37 to 0.84,

SD ¼ 0.3). A categorization from this HIb indicates

that there were 42.3% of right-handed infants, 0% left-

handed, and 57.7% non-lateralized.

Mean HIb was non-significantly higher for girls

(0.45) than for boys (0.31). Mean HIb was also non-

significantly higher when the mother was left-handed

(0.59) than when the father or no parent was left-

handed (0.35).

All infants categorized as right-handed from the

mean HIb were already categorized as right-handed

either at 8 months (n ¼ 7) or at 11 months (n ¼ 4).

A chi-square analysis to compare the classification at

8 months with the classification from the mean HIb

was significant (x2 (4) ¼ 6, p < 0.05). It thus seems

that by 8 months of age most infants already show a

hand preference representative of handedness during

the whole age period studied.

FIGURE 2 Set-up to evaluate handedness for pointing.


QHP Test. Figure 4 shows the percentage of right hand

grasping for each age group at each spatial position on

the QHP test. Two facts are apparent: first, the percent-

age of right-hand grasps increases from left to right;

second, at the middle position, there were globally

more than 50% right-hand grasps. An HI was calculat-

ed on the QHP test (HIqhp) for each position. It

increases from position 1 to 7 (�0.95, �0.86, �0.55,

0.33, 0.89, 0.96, 0.97, for positions 1, 2, 3, 4, 5, 6, 7,

respectively). An ANOVA on the mean HIqhp across

age with position (�7) as a repeated measure showed

a significant effect for position (F(6,150) ¼ 374,

p < 0.0000001). A post hoc LSD test showed that the

mean HIqhp was significantly different between all

pairs of positions except between 1 and 2 and between

5, 6, and 7. The mean HIqhp across all sessions and all

positions was 0.12 (�0.14 to 0.43, SD ¼ 0.13). This

positive mean HIqhp indicates that when reaching to

grasp toward various positions symmetrically distribut-

ed around them, infants tend globally to use their right

hand more. However, since none of the infants had a

mean HIqhp greater than 0.5 or lesser than �0.5, all

were non-lateralized on this task.

Mean HIqhp across positions did not change much

with age (0.17, 0.01, 0.10, 0.14, and 0.16 for 8, 11, 14,

17, and 20 months, respectively). An ANOVA on

HIqhp across positions with session (�5) as a repeated

measure on the 22 infants who did not miss a session

shows no significant effect (F(4,80) ¼ 1.39, p ¼ 0.24).

Comparison Between the Two Measures of Handedness.Since this is the first time that the QHP has been used

with infants, we checked whether the result on the

QHP was consistent with the results of the BbHtest.

The mean HI across positions on the QHP is lower

than the mean HI on the BbHtest (Fig. 3), which was

expected since the BbHtest is run only at the middle

position. A repeated-measures ANOVA on mean HI as

a function of the test (BbHtest vs. QHP) and age (�5)

indicates a significant effect for test (F(1,20) ¼ 26.9,

p < 0.0001), but no significant effect for age, and no

test � age interaction. In addition, the positive and sig-

nificant Spearman rank correlation between the two

mean HIs (r ¼ 0.59) indicates that the more the infants

are lateralized on the BbHtest, the more they use their

preferred hand on the QHP test, including to reach

for the object placed to the contralateral side. Thus, it

appears that the QHP test, although not very sensitive,

is nonetheless a valid tool to compare handedness for

grasping with handedness for pointing in infants.

Pointing

Frequency of Pointing. Infants were tested for pointing

starting at 11 months of age. At 11 months, 24 of the

26 infants could be tested. The two others were fussy

and the testing session had to be stopped. Nine of the

infants did not point at all, while 15 pointed at least

once; only three pointed at all five positions. The mean

number of pointing movements to the five targets at

this age was 1.46 (SD ¼ 1.7). Thus, the results of the

11-month-olds could not be interpreted for handedness.

Interestingly, the infants who pointed at 11 months

understood significantly more words (F(1,22) ¼ 5.4,

p < 0.05), and tended to produce more words

(F(1,22) ¼ 3.2, p ¼ 0.08) than those who failed to

point. For word production, a Cohen’s d (0.76) indicat-

ed that the effect, although not significant, is large.

The number of pointing movements per target

increased from 11 to 20 months (0.26, 0.79, 0.81, 0.81,

at 11, 14, 17, and 20 months respectively). An ANOVA

on the number of pointing movements per target as a

function of age indicated that the age effect is signifi-

cant (F(3,57) ¼ 20.3, p < 0.00001). A LSD post hoc

test shows that the effect is due to the difference

between 11 months and the three other ages. The corre-

lations between the number of pointing movements and

the number of words understood or produced by the

infants were always positive until the age of 20 months.

However, the only significant correlation was found at

17 months, between the number of pointing movements

FIGURE 3 Mean HI for grasping as a function of age:

comparison between BbHtest and QHP.

FIGURE 4 Percentage of right-hand grasping for each age

group as a function of object position on the QHP test.


and the number of words produced (r ¼ 0.55,

p < 0.05).

Handedness for Pointing ComparedWith Handedness for Grasping

Starting at 14 months of age, enough infants pointed

for the handedness of pointing to be evaluated. Out of

the 24 infants tested 14 months, 21 (87.5%) pointed at

least once, and 19 pointed between three and five times

and at least once to the left and once to the right. All

infants seen at 17 months pointed at least once and

23 pointed at least once to the left and once to the

right. At 20 months, it was slightly more difficult to

elicit pointing. Out of the 25 infants seen at 20 months,

three could not be properly tested for pointing because

of fussiness, and three did not point at each target or at

least did not point once to the left and once to the right.

In all, it was possible to evaluate handedness for point-

ing for 22 infants, among whom 15 were tested and

pointed in the three sessions, five were tested and point-

ed in at least two of the three sessions, and two could

be included when only the middle target was analyzed

but not on the other analyses because they did not point

on both sides in at least two sessions.

HIp was first calculated across positions for each

session. The mean HIp across positions slightly in-

creased with age (0.49, 0.61, and 0.68 for 14, 17, and

20 months, respectively, Fig. 5). However, an ANOVA

on HIp across positions with session (�3) as a repeated

measure on the 15 infants who pointed at the three

sessions showed no significant effect for session

(F(2,28) ¼ 1.04, p ¼ 0.36).

We compared handedness for pointing and handed-

ness on QHP test in three ways. First, we compared

mean HI across positions on the QHP and for pointing

in the same infants at 14, 17, and 20 months. HIp was

higher than HIqhp, as seen in Figure 5. A Student’s

t-test for matched samples showed that the difference

was significant at 14 months (t (18) ¼ �3.7, p < 0.01),

at 17 months (t (21) ¼ �3.7, p < 0.01), and at

20 months (t (17) ¼ �3.6, p < 0.01).

Thus, for the three ages at which the comparison

was possible, HI was significantly higher for pointing

than for QHP. Mean HI over the three sessions was

also significantly higher for pointing (0.58) than for

QHP (0.15; t (19) ¼ �6.1, p < 0.000001). Based on

the HI calculated on the pointing test at 14, 17, and

20 months, 70% of the infants were categorized as

right-handers and 30% were not lateralized. In contrast,

from the HI calculated on QHP test at 14, 17, and

20 months, 5.3% of the infants were categorized

as right-handers and 94.7% were not lateralized. These

two mean HIs were not significantly correlated

(r ¼ 0.41, Fig. 6).

Second, since the number of targets was different

between the two tasks, and since the angle between ad-

jacent targets was also different, we compared the an-

gle at which the infants switched hands to use the right

hand in the contralateral field. Figure 7 clearly indicates

that at the three ages for which infants were compared,

the shift was much further to the left for pointing than

for QHP.

Finally, we compared mean HIqhp and HIp across

the three sessions—14, 17, and 20 months—for the

middle target. A Student’s t-test for matched samples

indicated that HIp (0.68) was significantly higher

(t (21) ¼ �2.4, p < 0.05) than HIqhp (0.4). A compar-

ison for the three same sessions between HI at the

BbHtest and HIqhp (middle target) with the same

infants showed no difference between HIqhp and HIb

(0.43; t (21) ¼ �0.19, p ¼ 0.85). In contrast, HI was

significantly higher for pointing than for the BbHtest

(t (21) ¼ �2.39, p < 0.05). The percentage of right-

handers from the results at the middle target for the

three sessions was 50% right-handed, 45% non-lateral-

ized, and 4.5% (one infant) left-handed for QHP, and

68.2% right-handed and 22.7% non-lateralized for

pointing. The only significant correlation between HIs

at the three last sessions was between mean HIb and

mean HIqhp (r ¼ 0.50, p < 0.05).

DISCUSSION

The goal of the current study was to compare the devel-

opment of handedness for grasping objects and for

pointing to objects over a period when pointing

becomes part of the infant’s motor repertoire. The clas-

sical handedness test with objects presented in the mid-

dle showed the usual majority of right-handed infants

as compared with left-handed when HIb was calculated

over the five sessions. Handedness classification from

this HIb is well correlated with the classification atFIGURE 5 Mean HI for pointing and for grasping (QHP)

of the 15 infants having pointed at 14, 17, and 20 months.


8 months. Thus, by 8 months of age infants already

show a hand preference predictive of later handedness.

These results are in line with other studies showing that

hand preference for grasping can be observed during

the first year of life (Corbetta & Thelen, 1999; Fagard

& Lockman, 2005; Michel, Ovrut, & Harkins, 1985;

Michel et al., 2006). The fact that HIb fluctuates across

sessions also fits with previous results show fluctuations

in handedness during the first months of life (Corbetta

& Thelen, 1999; Fagard, Spelke, & von Hofsten, 2009;

Ferre et al., 2010).

The other handedness test, the QHP test, was

designed for comparison with handedness for pointing,

to test whether infants use their right hand more when

pointing at a faraway object presented on the left side

than when reaching to grasp an object presented closer

in on that side. On the QHP test, two tendencies were

observed: a tendency to reach with the hand ipsilateral

to the side of the object, and a weaker ipsilateral ten-

dency when the object was to the left than when it was

to the right. Thus, when reaching to grasp objects situ-

ated at various symmetrical positions around them,

infants tend globally to use their right hand more.

However, this global tendency was weak and led to the

categorization of all infants as non-lateralized. The

tendency to use the ipsilateral hand to grasp objects

presented to one side had been observed in previous

studies (Fagard et al., 2009), as had the fact that the

tendency is weaker to the left than to the right side

(Sacco et al., 2006). The lower HI on the QHP test

than on the classical BbHtest can be explained by the

fact that all seven items were in the middle positions

on the BbHtest, whereas they were at different posi-

tions in space on the QHP test. Presentation of objects

at all positions in space may have partly inhibited

right-hand preference. However, the significant correla-

tion between HIs for the two handedness tasks indicates

that the QHP test is a valid tool to measure handedness

for grasping, although a less sensitive one than the

BbHtest. This allowed us to compare handedness for

grasping and pointing in similar conditions in terms of

object positions (all around the infants) and number of

trials (one trial per position and per session).

Several comparisons between QHP and pointing

tests indicated a larger right-hand bias for pointing than

for grasping. First, the HI calculated for the three ses-

sions at which enough infants pointed to allow estima-

tion of handedness—14-month, 17-month, and 20-

month—was significantly larger for pointing than for

grasping. This means that globally, infants used their

right hand more to point to objects than to grasp them.

Second, the angle in the left hemifield at which infants

shifted to their ipsilateral hand was further to the left

for pointing than for grasping: this indicates that infants

FIGURE 6 Scatter plot of the relationships between mean HIqhp and HIp over the last three

sessions (14, 17, and 20 months).


are more willing to use their right hand in the contralat-

eral left hemifield for pointing than for grasping. Thus,

the right-hand bias is stronger for pointing, whereas the

ipsilateral bias is stronger for grasping. Finally, HI for

the middle target was also significantly larger for point-

ing than for grasping for the QHP test as well as for

the BbHtest. Thus, infants used their right hand to

grasp the object in front of them less often than to point

at it. In addition, the infant who was categorized as

left-handed for grasping the middle object at QHP

when only the results from the three last sessions were

taken into account mostly used her right hand to point

at the middle puppet. We checked that the more fre-

quent use of the right hand for pointing than for grasp-

ing did not simply reflect the use of a more precise

finger movement when pointing than when grasping. In

fact, the larger percentage of right-hand pointing as

compared with left-hand pointing holds for pointing

movements with the whole hand as well as for pointing

movements with the index. We also checked that this

difference was not due to priming induced by the use

of vocalization during pointing, and not during grasp-

ing. Overall, the right-to-left ratio is the same whether

or not pointing is accompanied with vocalizations.

Our results show more right-handedness for pointing

than for grasping are coherent with those of the

few extant studies that have compared handedness

for pointing and object manipulation. For instance,

Vauclair and Imbault (2009) observed that not only

right-handers but also left-handers for grasping tended

to use their right hand for pointing (see also Esseily et

al., in press, Cochet & Vauclair, 2010b). They also

found that the correlation between the two indices was

low except during key phases of language development.

In our study, the correlations between the two indices

(pointing and QHP) did not reach significance during

the last three sessions (14, 17, and 20 m), whether con-

sidered separately or together.

Thus, it appears that infants’ use of their right hand

for pointing cannot be considered as a simple conse-

quence of their use of the right hand to grasp objects.

In turn, use of their right hand for pointing does not

increase the frequency with which the right hand is

used for grasping. If we suppose that hand use for

pointing reflects language lateralization, this could

mean that, perhaps with the exception of a few key

periods for language development (Ramsay, 1985;

Vauclair & Imbault, 2009), the two functional asymme-

tries—for language and for grasping—becomes rela-

tively independent during the course of development.

This does not mean that both asymmetries may not

share some common inducing factors, but that they

then develop relatively independently afterwards, per-

haps due to the different constraints on their expression.

This relative independence would explain why a major-

ity of adults who are left-handed for object manipula-

tion share the same left-hemisphere bias for language

processing as right-handers (Gonzalez & Goodale,

2009; Hellige, 1993; Khedr, Hamed, Said, & Basahi,

2002; Knecht et al., 2000; Pujol, Deus, Losilla, &

Capdevila, 1999; Szaflarski et al., 2002).

A range of data from anatomical, fMRI, and behav-

ioral studies provide evidence that common factors

may underlie the two asymmetries. Among them are

the functional connections between cortical hand motor

areas and part of the language circuits; the fact that

Broca’s area is associated with non-language motor

functions such as planning or sequential behavior,

which are important for spoken language; and the fact

that words referring to arm (and tongue and leg)

actions activate areas along the motor strip that ‘‘either

[are] directly adjacent to or [overlap] with areas

activated by actual movement’’ (Hauk, Johnsrude, &

14 mo

0

20

40

60

80

100

-60 -40 -30 -20 0 20 30 40 60

% h

and

use

17 mo

0

20

40

60

80

100

-60 -40 -30 -20 0 20 30 40 60

% h

and

use

20 mo

0

20

40

60

80

100

-60 -40 -30 -20 0 20 30 40 60

Target angle

% h

and

use QHP LH

QHP RH

Point LH

Point RH

FIGURE 7 Shift between percentage of right-hand and

left-hand use for pointing and for grasping (QHP) at 14, 17,

and 20 months.


Pulvermuller, 2004, p. 301; see also Fadiga, Craighero,

Buccino, & Rizzolatti, 2002; Pulvermuller, Hauk,

Nikulin, & Ilmoniemi, 2005; Serrien, Ivry, & Swinnen,

2006). The fact that gestures typically accompany

speech also reinforces the notion of a link between the

two asymmetries (Iverson & Goldin-Meadow, 1998).

But what kind of link could there be between the

development of right-hand use for object manipulation

and of left-hemisphere specialization for language in

infants? The structural bases for both of these asymme-

tries seem to develop very early. Concerning language,

the planum temporale has been shown to be larger in

the left hemisphere in fetuses around the 30th week

(Chi, Dooling, & Gilles, 1977; Witelson & Pallie,

1973), and brain imaging studies have shown that the

language network is asymmetrical as early as 1 month

of age (Dehaene-Lambertz, Dehaene, & Hertz-Pannier,

2002; Dubois et al., 2009; Holowka & Petitto, 2002).

As regards sensorimotor pathways, the left corticospi-

nal tract (CST) has been observed to be larger and to

decussate higher in neonates from a postmortem study

(Yakovlev & Lecours, 1967). Similarly, two recent DTI

studies showed that the CST is larger from the left than

from the right hemisphere, in neonates (Liu, Baleriaux,

Kavec, Metens, Absil, Denolin, et al., 2010) and in 1-

to 4-month-old infants (Dubois, Hertz-Pannier, Cachia,

Mangin, Le Bihan, & Dehaene-Lambertz, 2009). As

regards handedness itself, sign of right-hand preference

is observed in utero around the 17th week. This could

reflect a left-hemisphere readiness to control sequential

movements already at that age. However, this right-

hand bias could also be a consequence of another

asymmetry, the head turning toward the right (Previc,

1991), which would facilitate right-hand activation. In

turn, more right-hand activity could preferentially

activate the left hemisphere, and lead to the left-hemi-

sphere specialization for motor control of sequential

movements. Such experience-dependent changes in

brain asymmetry have been demonstrated from early

development (Amunts, Schmidt-Passos, Schleicher, &

Zilles, 1997) as well as from pathology and extensive

training (Karni et al., 1995; Sanes & Donoghue, 2000;

Shahin, Bosnyak, Trainor, & Roberts, 2003). In conclu-

sion, the dynamic of the development in utero of a left-

hemisphere specialization for language and for con-

trolling hand sequential movements remains to be

explained. As one step to understand these relationship

between language lateralization and handedness, our

study compares the emergence of a stable hand prefer-

ence for grasping and for a communicative gesture

used prior to language and related to it, namely

declarative pointing. Our results show that when grasp-

ing and pointing are compared in similar conditions in

infants, with the objects presented in several spatial

positions, the tendency to use the right hand is signifi-

cantly greater for pointing than for grasping, and the

two hand preferences are only loosely correlated. This

suggests that, whatever the commonality of their origin

and the developmental dynamic of both types of later-

alization in utero, in infants the development of hand

preference for grasping and for a communicative

gesture such as pointing are relatively independent.

NOTES

We thank Lea Friedrich for her help in conducting the experi-

ment and analyzing the videos, and Viviane Huet for her help

for the statistics.

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