Hand-Use Preference for Reaching and Object ...

Genetic, Social, and General Psychologv Monographs, I I /(4), 407�427

Hand-Use Preference for Reaching and Object Manipulation in 6- Through 13-Month-Old Infants GEORGE F. MICHEL MARSHA R. OVRUT DEBRA A. HARKINS Developmental Psychobiology Unit, Department of Psychiatric Research Children's Hospital Medical Center, Boston

Abstract

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409

Method ............................... , ..................................... 412 Results

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Hand-Use Preference for Reaching and Object Manipulation in 6- Through 13-Month-Old Infants GEORGE F. MICHEL MARSHA R. OVRUT DEBRA A. HARKINS Developmental Psychobiology Unit, Department of Psychiatric Research Children's Hospital Medical Center, Boston

ABSTRACT. Validity, reliability, and stability of separate assessment of hand-use

preferences for reaching, object manipulation, and complementary bimanual action were determined for 6 through 13 month-old male and female infants. Only hand­ use preferences for complementary bimanual action varied with age. Females had more distinct hand-use preference than males but only for object manipulation. Con1parison of hand-use preference among these different scnsorimotor skills can provide a richer evaluation of infant handedness status required for systematic study of the development of neuropsychological functions during infancy.

HANDEDNESS IN ADULTS is not just an indicator of lateralized asym­ metry of motor coordination. It is also an aspect of hemispheric specialization of function (Beaumont, 1974) that is an important factor in assessments of hemispheric specialization for speech (Annett, 1975) and in the prognosis for recovery of function after unilateral brain damage (Hecaen, D e Agostini, & Monzon-Montes, 1981). Handedness is also related to patterns of cognitive style (Mebert & Michel, 1980; Newland, 1984; Peterson, 1979), specific learning disabilities (Geschwind & Behan, 1982; Nichols & Chen, 1981), and some developmental psychopathologies (Barry & James, 1978; Colby & Par­ kison, 1977). Although the causes of these associations are unknown (but see

Data collection for this study was supported in part by National Institute of Menral Health Grant IR03MH37749 to George F. Michel. Requests for reprints should be sent to George F. Michel, Dei·elopmental Psy­ chobiology Unit, Department of Psychiatric Research, Gardner House 5, Children's Hospital Medical Center, 300 Longwood Avenue, Boston, MA 02115. 409

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Genetic, Social, and General Psychology Monograph:>

Satz, Baymur, & Vlugt, 1979), it is conceivable that studies of the develop­ ment of handedness could disclose at least some of the reasons that handed­ ness is associated with particular patterns of cognitive skill and personality (Young, 1983). Developmental studies must begin with descriptions of the characteris­ tics of handedness from its earliest manifestations to its adult form. These descriptions, in tum, depend on reliable and valid techniques for assessing an individual's handedness status. Much research effort has been expended in providing valid assessment techniques for describing the handedness of chil­ dren and adults (e.g., Annett, 1972, 1978). Even modern studies of infant handedness, however, have employed assessment techniques that are idiosyn­ cratic to the researcher's own interests and orientations (e.g., Bresson, Maury, Pierault-Le Bonsiec, & Schonen, 1977; Coryell & Michel, 1978; Michel, 1981; Ramsay & Willis, 1984; Schonen, 1977). Researchers have reported infant hand-use preferences as too variable and unstable to be as­ sessed validly and reliably and, consequently, have asserted that infant hand­ edness cannot provide' accurate predictions of subsequent handedness status (Gesell & Ames, 1950; Hildreth, 1949). Yet, it must be during infancy that the foundations of the individual's handedness status are established because even 2-year-old children show hand-use preferences with most of the adult­ like characteristics (Annett, 1972; Connolly & Elliott, 1972; Hildreth, 1949). Although some modern researchers of infant handedness report frequent fluctuations of preference with age (Ramsay, 1984; Ramsay & McCune­ Nicolich, 1984; Ramsay & Willis, 1984), others report stability of preference during the same age period (Michel, 1982; Ramsay, 1980; Schonen, 1977; Young, 1977). The appearance of stability or instability in infant handedness may depend more on the types of sensorimotor skills assessed than on any inherent variability in the infant's handedness status. Even adult handedness may appear to be variable, depending on the demand characteristics of the tasks used for assessment (Flowers, 1975; Provins & Cunliffe, 1972). Differ­ ent manual skills are acquired at different ages during infancy, and each may exhibit unique patterns of development both in expression and in relation to the development of other skills (Uzgiris & Hunt, 1975). Therefore, descrip­ tions of infant handedness status should depend on the separate assessment of hand-use preferences for various types of manual skill. These separate as­ sessments may then be compared within and across age groups to provide a more complete description of handedness development during infancy. Reaching for objects is a manual skill that may be present at birth (Bower, 1982), at least in some rudimentary form (Hofsten, 1982). Visually guided reaching, however, is not elicited reliably until 4 to 5 months of age (Coryell & Michel, 1978; Field, 1977; Lasky, 1977), and at that time, infants will exhibit hand-use preferences (Michel, 1981, 1982). Reaching for objects is not only a well-established sensorimotor skill at 6 months but also gradually

Michel, Ovrut, & Harkins

411

becomes incorporated as a component in several more complex sensorimotor abilities during the subsequent 12 months (Uzgiris & Hunt, 1975). Therefore, a valid assessment of hand-use preference for reaching during this age period would provide the means for obtaining information about the relation of hand­ edness to the infant's acquisition of several important sensorimotor abilities. In contrast to reaching, unimanual manipulation of objects does not be­ gin to occur with any noticeable frequency until about S months of age, and hand-use preferences in object manipulation become apparent only about a month later (Ramsay, 1980). Ramsay ( 1984) has reported that the appearance of hand-use preferences for object manipulation coincides with the onset of repetitive babbling. This ontogenetic linkage between the manifestation of handedness in object manipulation and the occurrence of babbling could be important for understanding the association of handedness with hemispheric specialization of function. Unfortunately, Ramsay (1984) did not distinguish between those infants with significant differences between hands in object manipulation and those with relatively small asymmetries in hand use. A valid and reliable technique for assessing infant hand-use preferences for object manipulation would allow for the comparison of infants with and without hand-use preferences in investigations of the relation of handedness to the development of early speech skills. Complementary bimanual actions represent a new level of sensorimotor coordination for infants that is not required in reaching and unimanual manip­ ulation (Bruner, 1971). In this new level of coordination, the roles of the two hands are distinctly different. One hand supports or manipulates the object to facilitate the other hand's investigation of the object or its exploitation of the object's features. Such complementary bimanual action first appears at about 9 to 10 months of age (Bruner, 1971; Ramsay, Campos, & Fenson, 1979) but is not well established until 11 to 12 months. Hand-use preferences in these bimanual actions become manifest only during the 12 to 13-month period (Ramsay et al. 1979). To provide a valid and reliable description of the handedness status of 6- through 13-month infants, an assessment technique must be created that measures hand-use perferences in at least three manual skills: reaching for objects, manipulating objects, and coordinating complementary bimanual ac­ tions. These three skills should be assessed because each has been shown to reveal infant hand-use preferences and because each exhibits a somewhat dif­ ferent pattern of development during this age period. Reaching skill is estab­ lished well before the beginning of the infant's 6th month, unimanual manip­ ulation skill is established toward the beginning of the 6- to 13-month period, and complementary bimanual action skill is established toward the end of this period. In the present study, the validity and reliability of a handedness as­ sessment technique for infants 6 through 13 months of age were determined, and a description of infant handedness status during this period is presented.

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Genetic, Social, and General Psychologv Monographs

Method Subjects Ninety-six infants (48 males) were recruited from birth lists of the Beth Israel Hospital, Boston, and S t . Margaret's Hospital, Dorchester. Infants were se­ lected to meet the criteria of 12 infants (6 males) for each of the eight age groups (6 through 13 months) of the study design. Although scheduling dif­ ficulties produced a wider range of ages within each age group than had been anticipated, there was at least a 5-day separation of age ranges between ad­ jacent age groups: 6-month-olds, M

=

181 days, range

7-month-olds, M

=

205 to 231 days; 8-month-olds, M

=

283 days, range

=

=

217 days, range

250 days, range = 245 to 274 days; 9-month-olds, M 279 to 290 days; JO-month-olds, M I I-month-olds, M =

=

=

=

338 days, range

=

308 days, range

=

155 to 195 days;

=

=

295 to 320 days ;

326 to 343 days; 12-month-olds, M

372 days, range = 364 to 382 days; 13-month-o!ds, M

=

400 days, range

393 to 422 days. Within each age group, the male ages (in days) were not

significantly different from the female ages, F(7, 87)

=

0.87, p > .25; nor

were the ages of the males across age groups significantly different from those of the females, F(l , 87)

=

0.85, p > .25.

After checking the hospital records to ensure that the course of preg­ nancy and delivery were uneventful, parents were contacted initially by a letter explaining the study. Shortly thereafter, we telephoned the parents to answer any questions, to solicit their infant's participation, and to set an ap­ pointment time for their baby's visit to the laboratory. The parents were paid traveling expenses for the visit.

Apparatus Twenty-one common infant toys were used for the handedness test. The toys were selected to maximize the likelihood that the infant would reach for them and engage in some form of manipulation. Therefore, the toys were brightly colored, easily grasped, and some had moving parts or noise-generating fea­ tures . Several were selected because they potentially afforded complementary bimanual hand use (one hand provides support for the manipulation of the toy by the other hand). For 6 of the 28 toy presentations, pairs of identical toys were used to allow the infant to use both hands to reach for and to obtain a toy. Table I describes the toys in their order of presentation. To elicit and maintain block-play activity, six sets of five wooden blocks each were used. The blocks, similar to those described b y Forman (1982), consisted of narrow (3. 8-cm diameter) and wide (6.3-cm diameter) cylindri­ cal blocks and large (6.3 cm/side) and small (3 . 8 cm/side) square blocks, all 3. 8 cm high. All blocks within a set were the same color (red, blue, or ye!-

Michel, Ovrut, & Harkins

413

TABLE 1 Description and Order of Presentation of Toys Used to Assess Infant Hand-Use

Preferences for Reaching and l\1anipulation

I. 2. 3. 4. 5. 6. 7. S.

A plastic starfish A beaded bracelet A red dumbbell rattle A beaded necklace A pair of identical yellow dumbbell rattles A pair of identical rings each suspended by a stiff wire A small, red cube ( l.5 cm/side) suspended by a stiff wire and presented twice A large, blue cube (5 cm/side) with an attached small, red cube (1.5 cm/side) suspended by a stiff wire and presented twice in alternation with presentations of the small cube alone

9. A pair of identical strands of large pop-it beads (5 beads in each strand) \0. A small (3 cm tall) cylindrical wooden cage with a freely moving bell enclosed within l l. A pair of identical wind-up monkeys that played the cymbals 12. A set of plastic keys on a key chain

13. A bracelet and rattle combination presented twice with their left-right positions reversed for the second presentation 14. A hollow wooden ball (3-cm diameter) with six finger holes and a small, freely moving ball enclosed within 15. A plastic windmill (7.5 cm tall) 16. Stacking rings on a post 17. A push-button phone 18. A busy box (9 cm tall) that rotated on its base to provide four sides with different manipulanda 19. Three nesting cups (presented twice-once nested and once loose) 20. A xylophone presented four times-twice with the hammer placed in the infant's right hand and twice with the hammer placed in the left hand 21. A wind-up bird in a transparent box with an easily opened lid that was hinged to close unless held open

low). Each set was composed of a specific distribution of the different shapes presented to the infant according to one of four alternative series (cf. Forman, 1982, p. 106). A monochrome television camera (Panasonic WV 3082), sus­ pended from the ceiling at a distance of 1.7 m above a tan formica table (1.2 m x l . 8 m), provided an overhead view of the infant and the blocks. The videosignal was recorded on videotape by a Panasonic NV 3160 recorder for later analysis. Procedure

After greeting the parent and infant and describing the procedure, the infant was seated on a carpeted floor with the parent seated immediately behind,

414

Genetic, Social, and General Psychology Monographs

supporting the infant's hips if necessary. The first experimenter sat on the floor directly across from the infant at a distance of about I m. The infant's handedness was assessed by presenting to the infant 21 different toys (kept in a large cardboard box), one at a time, while a second experimenter recorded the hand used for the initial grasp of the toy (reaching) and the characteristics of hand use during the 20-c period after grasping the toy (manipulation). Four toys were presented more than once for a total of 28 presentations. For 6 presentations, pairs of identical toys were presented simulta­ neously, each one in line with one of the infant's shoulders. For the other 22 presentations, a single toy was presented in a position midline to the infant's orientation. For 5 presentations, the toys were presented at shoulder height, suspended by a stiff wire held by the experimenter. For the other 23 presen­ tations, the toys were presented on the floor immediately in front of the infant. Each infant received the same order of toy presentation, which represented increasing complexity in the toys' characteristics and variability in the types of actions required for retrieval and manipulation. This handedness test took less than '15-min to administer and never disturbed the infants. To determine the relative validity of the handedness test, 64 of the 96 infants (28 females) were also selected to participate in block-play activity. Each infant sat on the mother's lap, sometimes on cushions so that the table top was at the infant's waistline, in front of the table. Before the first set of blocks was presented to the infant, the mother was reminded that she should not intervene in any way while the child was playing with the blocks. An experimenter retrieved and replaced any blocks that fell to the floor. The videorecorder was started the moment the first set of blocks was placed on the table in front of the infant. One experimenter sat across the table from the infant, encouraged him or her to play with the blocks, and kept track of 60 s with a concealed stopwatch. At the end of the 60-s play period, another experimenter paused the videotape while the experimenter removed the blocks to an empty carton. Videotaping resumed when the next set of five blocks was placed in front of the infant. Thus, each infant provided 6 min of videotaped block play. These videotapes were analyzed, in slow motion, to provide precise data on the frequency of right- and left-hand use. These data were then compared to the data from the handedness test as a measure of the validity of the handedness test. The reliability of the measures of hand-use preference provided by the handedness test was assessed in three ways. Internal consistency of the test was determined by using the odd-even split-half reliability measure. Prefer­ ence scores were calculated for each of the 96 infants first for the even­ numbered presentations and then for the odd-numbered presentations. These scores were then compared by a Pearson correlation coefficient, corrected by the Spearman-Brown prophecy formula. Test-retest reliability was deter­ mined by presenting the handedness test twice (once at the beginning of the

Michel, Ovrut, & Harkins

415

visit and again at the end) to a random selection of 16 infants (8 males). The hand-use preferences for each assessment were compared by a chi-square test and the contingency coefficient. The stability of the assessments provided by the handedness test was determined by comparing the hand-use preferences of IO infants (5 initially assessed as right-handed and 5 initially assessed as left-handed) across three of the eight age groups (7, 9, and l l months). The proportion of infants with consistent hand-use preferences across these three age groups was used as a measure of the stability of the assessment.

Coding

During the handedness assessment of 20 randomly selected infants, two ex­ perimenters simultaneously and independently recorded hand use. For each presentation, the proportion of agreement between the two coders about the hand used to make initial contact with the item ranged from . 9 to 1.0 (1.0 was the proportion of agreement for 21 of the presentations). The proportion of agreement on relative hand use during the manipulation (shaking, banging, fingering, etc., of the object by one hand) of each presented item also ranged from .9 to 1.0, but the number of presentations with perfect agreement fell to 15. Disagreement on manipulation did not occur, however, because the coders identified opposite-hand use. Rather, disagreement occurred because an ac­ tion of a hand was not noted by one of the coders. Intercoder disagreement in recording initial contacts (reaching) occurred because one coder recorded the initial contact as simultaneously involving both hands, whereas the other coder recorded a precedence of one hand. For each presentation, the coders also recorded the instances of complementary bimanual hand use (one hand manipulates the object while the other supports it). The proportion of agree­ ment between coders was perfect for each occurrence of bimanual handed­ ness. Thus, for each infant, each of the 28 presentations provided a reliable indication of the hand used to make initial contact with the item, the predom­ inant hand used during unimanual manipulation of the object, and relative hand use during complementary bimanual manipulation. Hand-use preference scores were calculated for each infant for each of the three manual activities recorded during the handedness assessment (reach­ ing, manipulating, and coordinating). The scores for each activity were de­ rived by first separately summing the right and left uses across the 28 presen­ tations. Then, the sum of the left uses was subtracted from the sum of the right, and the difference was divided by the square-root of the total. This formula provides the equivalent of a z score, with positive scores indicating a right-hand-use advantage and negative scores indicating a left-hand-use ad­ vantage. No previous research has produced evidence that the specific size of the

416

Genetic, Social, and General Psychology Monographs

preference score indicates anything about the strength of the infant's prefer­ ence. The size of the score may, however, be used for classifying the infants. Infants with preference scores of 1.65 or more were classified as right­ handed, whereas those with scores between 1.0 and l.65 were classified as right-biased. Infants with scores between 1.0 and - 1.0 were classified as having no hand-use preference. Those infants with scores between -1.0 and - 1. 65 were classified as left-biased, whereas those with scores less than - 1.65 were left-handed. Thus, the hand-use preference scores were used to assign a handedness status to the infant for each of the three manual activities. Although preference scores varied slightly between the two coders, there was I 00% agreement in the assignment of a handedness status for each manual activity. Hand-use preference scores for manipulation were generated by simply counting the frequency of left and right actions recorded during the 20 s after each presentation. Then, the hand used most frequently was identified with that presentation (or both was noted if each hand was used with the same frequency). Depending on the degree of manual activity with an item, this scoring procedure could tend either to accentuate or to blur differences in use between hands. This technique, however, may provide an assessment of hand-use during manipulation that does not require the more reliable and ac­ curate, but tedious, coding of slow-motion filmed or videotaped activity. The videotapes of the block play were played back for coding at slow speed on a 9-in. Panasonic monitor. The hand used for 10 different move­ ments was recorded on a checklist each time a movement occurred: I, pick up a block; 2, transfer a block to the other hand; 3, shake a block; 4, hold a block for visual inspection; 5, bang a block on the table or another block; 6, throw a block; 7, repetitively scrape a block back and forth on the table; 8, push a block away from infant; 9, pull a block to infant; and IO, reorient a block. The frequencies of right- and left-hand use for Movement I were calcu­ lated across the six block sets for each infant and used to calculate a hand-use preference z score. These scores were used, as in the handedness assessment, to assign a handedness status to the infant for hand use during the first move­ ment. The frequencies of right- and left-hand use for the other movements were combined to provide a measure of manual activity for each infant during block play. Hand-use preference z scores were calculated for manual activity and used to assign a handedness status to each infant. Two coders independently scored the hand used for the 10 movements during the block play of 28 of the 64 infants in this phase of the study. The separate hand-use preference scores for "pick up" and "manual activity" that were derived by each coder for these infants were compared by a Pearson correlation coefficient. The correlation was .99 for the pick-up preference scores and .99 for the manual activity scores. Therefore, hand-use preference

Michel, Ovrut. & Harkins

417

scores for picking up blocks and for playing with blocks were reliably coded from videotape. Handedness for pick up and manual activity during block play was as­ sessed separately to provide measures of spontaneous hand use that would be somewhat equivalent to the reaching and manipulating hand-use assessed by the handedness test. Results Spontaneous Hand-Use Preferences During Block Play

More infants (76%) showed hand-use preferences for picking up blocks dur­ ing play than would be expected by chance (z = 3. 3). For 4 7%, the difference in frequency of use between the hands was significant (Figure I); 67% of these infants were significantly right-handed, whereas 33% were left-handed. V.'hen those with right-handedness were combined with those with a right bias,the majority of infants (51%) showed a right-hand-use preference. There was no significant association of the infant's sex with hand-use preference for picking upblocks,x'(4,N=64) = 4.6,p> .10.

PERCENT 75

� � D � �

RIGHT HANDED RIGHT BIASED

50

NO PREFERENCE LEFT BIASED LEFT HANDED

25

,.__ PICK-ll? BLOCKS

MANUAL ACTION

HANDEDNESS STATUS

FIGURE I. Distribution of handedness status for two sensorimotor activ­ ities (picking up blocks and active manual maneuvering of the blocks) during block play for infants 6 to 13 months of age (n = 64).

418

Genetic, Social, and General Psychologv Monographs

More infants (70%) also showed hand-use preferences for manual activ­ 3.1). The dif­ ity during block play than would be expected by chance (z ference in use between the hands was significant for 47% (Figure I), with 71% of these infants being significantly right-handed and 29% being left­ handed. Although there was no association of the infant's sex with hand-use 6.8, p > .10, the distri­ preference during manual activity x'(4, N = 64) bution prompted further analysis. A significantly greater proportion of fe­ males (59%) than males (33%) had right-hand-use preferences for manual 2.0). The proportion of males (29%) with left-hand-use prefer­ activity (z ences, however, was not significantly different (z = 1.2) from that of females (18%). Thus, there is some suggestion that right-hand-use preference for manual activity may be more common in female than male infants (see Fig­ ure 2). Hand-use preferences for picking up blocks were significantly associated with hand-use preferences for manual activity during block play, x'( 16, N 64) = 61.1, p < .001, r .74. Only 2% of the infants showed discor­ dant hand-use preferences for these two types of manual skill during block play. =

=

=

=

=

Assessing Hand-Use Preferences for Reaching

The internal consistency for assessing hand-use preferences for reaching was high (r .85). Although significant, the test-retest reliability was not partic­ ularly strong, x'(4, N = 16) = 10.0, p < .05. No infant alternated left- and right-hand-use preferences between the two assessments. Rather, the prefer­ ence scores alternated with a no-preference score. The stability of the reach­ ing assessment was high(. 90), with only one infant showing a single fluctua­ tion of preference across three age groups. This fluctuation was not between a right- and left-hand-use preference; rather, at 9 months, one of the right­ handed infants obtained a no-preference score. A significant majority of infants (78%) showed a hand-use preference for reaching (z = 5 .4). The proportion of infants with a hand-use preference for 5.5, p 96) reaching did not change significantly with age, x'(7, N >.IO. The majority of infants (53%) preferred to use their right hand for reaching, and only 18% preferred to use their left hand (Figure 3). Of those infants with a hand-use preference, there was a significant bias (z = 3.7) to prefer the use of the right hand (69%). The relative proportion of right- and left-hand-use preferences did not differ significantly across the eight age groups, x'(28, N 96) = 31.9,p > .25. Although the proportion of females with right-hand-use preferences (61%) was greater than that of males (46%), the difference was not significant (z = 1.5). The proportion of males with left-hand-use preferences (27%) also =

=

=

=

PrntENl

50

�MALES �FEMALES

30

10 RJSHT 1waD

lllIIHT IIA!m

NO �

lEf'T 8IASEll

HANDEDNESS STATUS

FIGURE 2. Relation between preferred hand use for active maneuvering of blocks and the sex of the infant.

PERCENT

75

� RIGHT HAND-USE D � LEFT NO PREFERENCE

H.6.tm-USE

0 FEACHINB

MANIPl.U.TlOH

BIHANUAL ACTION

SENSOR!MOTOR SKILL

FIGURE 3. Distribution of hand-use preferences of infants 6 to 13 months of age (n = 96) as determined during assessment of reaching, object ma­ nipulation, and complementary bimanual action skills.

419

420

Genetic, Social, and General Psychologv Monogra p hs

was not significantly larger than that of females (22%). Thus, hand-use pref­ erences for reaching did not differ according to the sex of the infant. There was a significant association of hand-use preferences for reaching with those for picking up blocks during play, x'(16, N = 64) 36.65, p < .O l , r = .62. Assessment of hand-use preferences for reaching identified perfectly the hand-use preferences for picking up blocks for 52% of the in­ fants. Assessment of hand-use preferences for reaching only misidentified the preferences for picking up blocks in 8% of the infants. The remaining 40'7c had no-preference scores during either block play or on the handedness as­ sessment. Hand-use preferences for reaching were not significantly asso­ ciated with hand-use preferences for manual activity during block play, x'( 4, N = 64) = 7.7,p> . IO, r = .33. =

Assessing Hand-Use Preferences for Manipulating

The internal consistency for assessing hand-use preferences for manipulating was lower than that for reaching, but it was still at an acceptable level (r = .77). Test-retest reliability was significant, x'(4, N = 16), 9.7, p < .05, r = .61; but 25% of the 16 infants showed no preference for each assessment. The stability of the hand-use preference for manipulation was not marked (.60). Four of the infants had at least one no-preference score across the three age groups, and one showed an opposite-hand-use preference at 9 months. The assessment test showed that a significant majority of infants (71%) had hand-use preferences for object manipulation (z = 4.0). The proportion of infants with hand-use preferences for manipulation did not change with 8.1, p > .10. Among the infants with a hand-use age, x'(4, N = 96) preference, there was a significant bias (z = 2.8) toward the preferred use of the right hand (67%). Only 15% of the infants were left-handed, whereas 30% were right-handed, and 21% were right-biased (Figure 3). The relative proportion of right and left hand-use preferences did not differ across the eight age groups, x'(l4, N = 96) = l 1.9, p > .25. Only 25% of the males had significant hand-use preferences, as compared to 59% of females (z 3.3). There were significantly (z 2.4) more right-handed females (39%) than right-handed males (17%) and significantly (z 2.4) more left-handed fe­ males (20%) than left-handed males (8%). Indeed, significantly more males (75%) than females (41%) had less distinct hand-use preferences for manip­ ulating toys (z = 3.3). The relative proportion of right- and left-hand-use preferences did not vary with age group for either males, x'(l4, N = 48) 48) = 16.6, p > .25 (see Figure 4). 14.0, p > .25, or females, x'(l4, N Hand-use preference for manipulation was significantly associated with hand-use preference for manual activity during block-play, x2(4, N = 64) 9.5, p < .05, r = .36. As with reaching, the assessment test identified per=

=

=

=

=

=

=

=

Michel, Ovrut, & Harkins

421

�lo!ALES �FEMALES 50

RIGHT HANIHJSE

NO PREFERENCE

LEFT HANO-USE

HANDEDNESS STATUS

FIGURE 4. Relation between handedness status for object manipulation and the sex of the infant.

fectly hand-use preferences for manual activity during block play for 52% of the infants and misidentified the preferences for 10% of the infants. Hand-use preferences for manipulating were associated significantly with those for picking up blocks,x'(4,N = 64) = 12.7,p< 025, r = .45. .

Assessing Hand-Use Preferences for Coordinating Bimanual Action

As expected, bimanual action did not occur with any measurable frequency until late in the 1st year, and it was not a typical motor skill of all infants until 32), 59% month 13 (Figure 5). Of all infants showing bimanual action (n had right-hand-use preferences, and 22% had left-hand-use preferences. Fig­ ure 6 shows the distribution of hand-use preferences for five age groups. A right-hand-use preference predominated at 13 months when all infants were engaging in bimanual action. Unfortunately, bimanual action occurred too infrequently during block play to allow measurement of spontaneous hand-use preference. Therefore, there was no measure of the validity of the handedness test's assessment of hand-use preferences for bimanual action. The present results were, however, similar to those reported by Ramsay et al. (1979). =

PERCENT 100

75

50

25

e

9

10

II

12

13

AGE IN MONTHS FIGURE S. Relation between age and the percentage of infants showing complementary bimanual action during the test of handedness.

PERCENT "'

�RIGHT 11AN0-US= ONO PREFERENCE �LEFT HAND-USE

25

0 g

••

" AGE

IN MONTHS

FIGURE 6. Relation between preferred hand use for complementary bi­ manuaf action and the age of the infant.

422

Michel, Ovrut, & Harkins

423

Hand-Use Preferences Compared for the Three Manual Skills

Hand-use preferences for reaching were significantly associated with those for manipulating, x'(4, N = 96) = 32.9, p < .01, r = .52. This association 48) = 13.96, p < .01, r = .48, was significant for both males, x2(4, N and females, x'(4, N = 48) = 22.9, p < .01, r = .59. The hand-use pref­ erences for reachin g and m anipul ating were identical for 60% of the infants and discordant for only 5% of the infants. Hand-use preferences for manipulating were significantly associated with those for coordinating bimanual action, x'(4, N = 32) = 23.3, p < .001, r = .61. The preferences for these two assessments were identical for 70% of infants and discordant for only 4% of the infants. ln contrast, hand­ use preferences for reaching were not significantly associated with those for coordinating bimanual action, x'(4, N = 32) = 7.5, p > . IO. The prefer­ ences for the two assessments were identical for 50% of the infants, but they were discordant for 18% of the infants. All but one of the infants with discor­ dant h and-use preferences, however, were in the 13-month age group. In­ deed, the 12- and 13-month groups were significantly different in their rela­ tive frequency of infants with concordant and discordant hand-use preferences for reaching and coordinating bimanual action, x'(1, N = 24) 4.4, p < .05. Thus, discordance of hand-use preference for reaching and coordinating bi1nanua\ action was associated pri1narily with that age group (13 months) for which bimanual actions were most likely to occur. =

=

Discussion

The handedness test used in this study achieved acceptable levels of reliability and validity. By separately assessing hand-use preferences for three different sensorimotor skills, the test provided a detailed description of the pattern of infant handedness during the 6- through 13-month period. The test allowed identification of infants without hand-use preferences for comparison with infants with hand-use preferences. In general, the test revealed that most infants manifested hand-use pref­ erences for reaching for and manipulating objects during this age period and that the majority showed a preference for using their right hand. Therefore, the right bias in human handedness was present by 6 months of age and did not seem to change during the subsequent 7 months. Although complemen­ tary bimanual action was confined to the second half of the 6- through 13month period, infants showed handedness characteristics for bimanual action that were similar but not identical to those found in manipulating and reaching. Because manipulation and bimanua\ action were assessed during the 20s period after the infant initially grasped an item, the hand-use preferences for

424

Genetic, Social, and General Psychology Monographs

manipulation and complementary bimanual action may have been constrained by the preference for reaching. This potential confounding between reaching and manipulating can be eliminated by including item presentations that begin by placing one of a pair of identical items in each of the infant's hands and recording subsequent manual activity. The advantages and disadvantages of this adjustment technique are being examined in a current study. Because the hand-use preferences for manipulation were associated with those for manual activity during block play, it is unlikely that the hand-use preferences for ma­ nipulating were simply derivatives of those for reaching. Although some of the motor actions recorded for manual activity during block play required first the picking up of a block, and hence were also potentially constrained by preferences for picking up blocks, many of the motor actions in manual activ­ ity did not require picking up a block. Moreover, the time period for block play allowed ample opportunity for the infant to switch manual actions be­ tween the hands. Therefore, we believe that the test does provide a fairly accurate assessment of hand-use preferences during manipulation. Comparing infant handedness status across the three sensorimotor skills reveals some interesting patterns. For example, the handedness status of males and females did not differ for reaching skills. Sex differences were apparent, however, in the hand-use preferences for manipulating. Because of the 20-s time constraint on manipulation during testing, the sex differences might not represent differences in handedness status. It may be that males were quicker than females in engaging the use of their other hand after ini­ tially grasping the item. This time constraint would account for the less dis­ tinct differences in use between the hands for males. Therefore, the test would be identifying potential sex differences in the speed of employment of sen­ sorimotor skills rather than sex differences in handedness status. Neverthe­ less, because sex differences in handedness were observed for manual activity (but not for picking up blocks) during block play when speed of employing sensorimotor skills was a less relevant factor, the test may have identified a sex difference in handedness for manipulation. Infants with a right hand-use preference for reaching predominated over those with a left preference for every age except 13 months. These data might be interpreted as showing that hand-use preferences may fluctuate at 13 months. But comparison of hand-use preferences for reaching with those for coordinating bimanual action may help to understand the reason for the change at I 3 months. Hand-use preferences for reaching and coordinating bimanual action were seldom discordant during the 9- through 12-month pe­ riod. Indeed, they were always concordant at 12 months, when bimanual ac­ tion began to become a more common skill in the infant's sensorimotor rep­ ertoire. At 13 months, however, hand-use preferences for reaching and coordinating bimanual action were predominantly discordant. Does the infant have two different handedness statuses at 13 months?

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Researchers have argued that mastery of a sensorimotor skill allows it to be incorporated into a network of other mastered skills (Piaget, 1952). One feature of this incorporation is that formerly independent skills may now in­ fluence one another's expression (Bruner, 1971; Piaget, 1952). It is likely that by 13 months reaching and coordinating complementary bimanual action are mutually incorporated skills (Uzgiris & Hunt, 1975). Because reaching is the simpler, more practiced skill, many of the reaches by 13-month infants may have involved the use of the nonpreferred hand so that the less practiced, more complicated, but more informative, bimanual action could begin im­ mediately without violation of the infant's handedness status. Subsequent re­ search is planned to address this issue. The brief, but valid and reliable, technique for assessing infant handed­ ness presented in this study can provide useful descriptions of infant hand­ edness status that are not constrained by the specific objectives or interests of a particular researcher. A test of handedness that allows assessment of three different manual skills for comparison with the development of other psycho­ logical characteristics during infancy may help disclose how handedness comes to be associated with so many neuropsychological functions. Thus, studies of the development of handedness during infancy address issues rele­ vant for both theoretical accounts of brain-behavior relations and their clinical application.

REFERENCES

Annett, M. (1972). The distribution of manual asymmetry. British Journal of Psy­ chology, 63, 343-358 . . Annett, M. (1975). Hand preference and laterality of cerebral speech. Cortex, 11, 305-328. Annett, M. (1978). Genetic and non gcnctic influences on handedness. Behavior Ge­ netics, 8, 227-249. Barry, R., & James, A. (1978). Handedness in autistics, retardates, and normals of a wide age range. Journal of Autism and Childhood Schizophrenia, 8, 315-323. Beaumont, J. (1974). Handedness and hemisphere function. In S. Dimond & J. Beaumont (Eds.), Hemisphere function in the human brain (pp. 89-120). New York: Wiley. Bower, T. G. R. (1982). Development in infancy (2nd ed.). San Francisco: Freeman. Brcsson, F., Maury, L., Picrault-Le Bonsiec, G., & Schonen, S. de. (1977). Orga­ nization and lateralization of reaching in infants: An instance of asymmetric func­ tion in hand collaboration. Neuropsychologia, 15, 311-320. Bruner, J. S. (1971). The growth and structure of skill. In K. J. Connolly (Ed.), Motor skills in infancy (pp. 245-269). New York: Academic Press. Colby, K., & Parkison, C. (1977). Handedness in autistic children. Journal of Au­ tism and Childhood Schizophrenia, 7, 3-9. Connolly, K., & Elliott, J. (1972). The evolution and ontogeny of hand function. In N. B. Jones (Ed.), Ethological studies of child behaviour (pp. 329-383). New York: Cambridge University Press.

426

Genetic, Social, and General Psychology Monographs

Coryell, J. F., & Michel, G. F. (1978). How supine pcstural preferences of infants can contribute toward the development of handedness. Infant Behavior and Devel­ opment, 1, 245-257. Field, J. (1977). Coordination of vision and prehension in young infants. Child De­ velopment, 48, 97-103. Flowers, K. (1975). Handedness and controlled movement. British Journal of Psy­ chology. 66, 39-52. Forman, G. E. (1982). A search for the origins of equivalence concepts through a microanalysis of block play. In G. E. Forman (Ed.), Action and thought (pp. 97136). New York: Academic Press. Geschwind, N., & Behan, P. (1982). Left-handedness: Association with immune disease, migraine, and developmental learning disorder. Proceedings of the Na­ tional Academy of Science, U.S.A 79. 5097-5100. Gesell, A., & Ames, L. B. (1950). Tonic neck reflex and symmetrotonic behavior. Journal of Genetic Psychology, 70, 155-175. Hecaen, H., De Agostini, M., & Monzon-Montes, A. (1981). Cerebral organization in left-handers. Brain and Language, 12. 261-284. Hildreth, G. (1949). The development and training of hand dominance: I, II, ill. Journal of Genetic Psychology, 75, 197-275. Hofsten, C. von (1982). Foundations for perceptual development. In L. P. Lipsitt & C. K. Rover-Collier (Eds.), Advances in infancy research (Vol 2, pp. 241-265). Norwood, NJ: Ab lex. Lasky, R. E. (1977). The effect of visual feedback of the hand on the reaching and retrieval behavior of y oung infants. Child Development. 48, 112-117. Mebert, C. J., & Michel. G. F. (1980). Handedness in artists. In J. Herron (Ed.), Neuropsychology of left-handedness (pp. 273-280). New York: Academic Press. Michel, G. F. (1981). Right-handedness: A consequence of infant supine head­ orientation preference? Science, 212. 685-687. Michel, G. F. (1982). Ontogenetic precursors of infant handedness. Infant Behavior and Development. 5. 156. Newland, G. A. (1984). Left-handedness and field-independence. Neuropsycholo­ gica, 22, 617-619. Nichols, P., & Chen, T. (1981). Mi'nimal brain dysfunction: A prospective stud): Hillsdale, NJ: Erlbaum. P eterson, J. M. (1979). Left-handedness: Differences between student artists and scientists. Perceptual and Motor Skills. 48. 961-962. Piaget, J. (1952). The origins of intelligence in children. New York: International Universities Press. P rovins, K. A & Cunliffe, P. (1972). The reliability of some motor performance tests of handedness. Neuropsychologica, 10, 199-206. Ramsay, D. S. (1980). Onset of unimanual handedness in infants. Infant Behavior and Development, 3, 377-385. Ramsay, D. S. (1984). Onset of duplicated syllable babbling and unimanual hand­ edness in infancy: Evidence for developmental change in hemispheric specializa­ tion? Developmental Psychology, 20, 64-71. Ramsay, D. S., Campos, J. J., & Fenson, L. (1979). Onset of bimanual handedness in infants. Infant Behavior and Development, 2, 69-76. Ramsay, D. S., & McCune-Nicolich, L. (1984). Fluctuation in bimanual handed ­ ness in the second year of life. Manuscript submitted for publication. Ramsay, D.S., & Willis, M. P. (1984). Organization and lateralization of reaching in infants: An extension of Bresson et al. Neuropsychologia, 22. 639-641. .•

.•

Michel, Ovrut, & Harkins

427

Satz, P., Baymur, L., & van der Vlugt, H. (l 979). Pathological left-handedness: Cross-cultural tests of a model. Neuropsychologia, 17, 77-81. Schonen, S. de. (1977). Functional dissymetries in the development of bimanual coordinations in human infants. Journal of Human Motor Studies, 3, 144-156. Uzgiris, I. C., & Hunt, J. McV. (1975). Assessment in infancy. Chicago: University of Illinois Press. Young, G. (1977). Manual specialization in infancy: Implications for lateralization of brain function. In S. J. Segalowitz & F. A. Gruber (Eds.), language develop­ ment and neurological theory (pp. 289-311). New York: Academic Press. Young, G. (1983). Changes, constancies and continuities in lateralization develop ment. In G. Young, S. Segalowitz, C. Corter, & S. Trehub (Eds.), Manual spe­ cialization and the developing brain (pp. 401- 404). New York: Academic Press.

Received April JO, 1985