Lauren Julius Harris

Cultural influences on handedness: Historical and contemporary theory and evidence.

Publisher Summary This chapter discusses the cultural influences on handedness. Right-handers comprise the vast majority of the adult population. Judging from the depictions of hand use in the works of art and from the analysis of the design of weapons, tools, and other historical artifacts, they also would seem to have been the norm since prehistoric time. Handedness represents the end-product of a long and multifaceted biosocial process. The environmental role can be studied in a number of ways. One way is through direct observation of the development of hand use in the context of the social and cultural environment. Direct observations might reveal whether parents are encouraging this preference by their own actions. Observations also could be made at the preschool and school-age periods and in every social situation throughout the life span. Older children and adults can be asked directly whether their hand preference has been encouraged or discouraged, and with what result, and inquiries can be made of teachers and school administrators as to their policies and practices. Cross-cultural surveys of the prevalence of left-handedness offer another way to measure the environmental role. The reason is that, although all cultures are designed for the right-hander, the rules are applied more liberally, or flexibly, in some cultures than in others.

Development of the infant's hand preference for visually directed reaching: Preliminary report of a longitudinal study

The development of hand preference in infancy was investigated longitudinally by using a visually-directed reaching task. Thirty-two infants, equally divided into groups of familial right- and left-handed boys and girls, were tested every 3 weeks from 24 to 39 weeks of age and once again at 52 weeks. Group trends for the development of hand preference were differentiated by familial handedness and sex of the infant. At all ages, test object position (to the infants right or left) strongly influenced the hand used for reaching. Marked variability both between and within infants demonstrated an instability of early hand preference, an effect that could be appreciated fully only with a prospective longitudinal design. The results thus suggest that the development of hand preference for reaching is highly variable, discontinuous, and related to the interaction of sex and familial handedness.

Within-individual variability in neurocognitive performance: Age- and sex-related differences in children and youths from ages 8 to 21

OBJECTIVE The transition from childhood to adulthood is characterized by improved motor and cognitive performance in many domains. Developmental studies focus on average performance in single domains but ignore consistency of performance across domains. Within-individual variability (WIV) provides an index of that evenness and is a potential marker of development. METHOD We gave a computerized battery of 14 neurocognitive tests to 9138 youths ages 8-21 from the Philadelphia Neurodevelopmental Cohort. RESULTS As expected, performance improved with age, with both accuracy and speed peaking in adulthood. WIV, however, showed a U-shaped course: highest in childhood, declining yearly into mid-adolescence, and increasing again into adulthood. Young females outperformed and were less variable than males, but by early adulthood male performance matched that of females despite being more variable. CONCLUSION We conclude that WIV declines from childhood to adolescence as developmental lags are overcome, and then increases into adulthood reflecting the emergence of cognitive specializations related to skill-honing and brain maturation.

Hand preference for visually guided reaching in human infants and adults

As the collection of new research reports in this volume shows, the question of handedness in non-human primates has become a subject of intense interest among psychologists and primatologists. The historical evidence also shows that this interest is of long standing (see Harris, Ch. 1, this volume). Still, the question remains controversial. There is a measure of agreement that individual animals show reliable hand preference but no consensus that this is a species characteristic.

Cerebral control for speech in right-handers and left-handers: An analysis of the views of Paul Borca, his contemporaries, and his successors

According to several recent historical accounts, Broca (1865a) stated that left-handers are the mirror-reverse of right-handers for cerebral control of speech, with the right hemisphere being dominant in left-handers, and the left hemisphere dominant in right-handers. The same accounts then note Brocas error in light of current evidence that the majority of left-handers are left-dominant for speech just as are nearly all right-handers. Eling (1984) has called such statements misrepresentations of Brocas position and has argued that Brocas analysis actually was more compatible with the current view that there is a disjunction, meaning an absence of an intimate anatomical relationship, between cerebral control for handedness and speech. The current paper looks again at Brocas work, describes the context in which his views were first articulated, and traces the development of the mirror-reversal principle. The conclusion is reached that, judged by a narrow reading of the 1865 paper, Brocas views could indeed be construed as an anticipation of the modern disjunction principle. However, judged by a broader reading, by consideration of his other writing, and in the context of the philosophical and scientific tradition that shaped his work, it is suggested that it was the mirror-reversal principle to which Broca was actually disposed.

In fencing, what gives left-handers the edge? Views from the present and the distant past

Recent studies show that in the sport of fencing left-handers have an advantage over right-handers. This was recognised by fencing masters as early as the sixteenth century. They also agreed that the advantage was due to left-handers’ numbers—that being a minority gave them more opportunities to compete against right-handers than right-handers had against them. Fencing masters today have reached the same conclusion, as have laterality researchers, who see the advantage as an example of what is now called a “frequency-dependent” effect. However, some researchers have also suggested other possibilities that relate the advantage to natural differences in ability. This article presents a sampling of views of fencing masters from the past, along with a summary and analysis of explanations, old and new.

Is maternal depression related to side of infant holding

Studies show that 65–85% of mothers hold their infants on the left side of their own body and that this left-bias may be reduced or reversed when mothers have symptoms similar to depression or dysphoria (de Château, Holmberg, & Winberg, 1978). No studies, however, have used diagnostic criteria to assess the mother’s psychological state. The current study examined the relationship between maternal report of depressive symptoms on the Beck Depression Inventory and holding-side bias in a high-risk sample of 177 mothers participating with their infants in a larger longitudinal study of mother–infant relationships and domestic violence. Mothers classified as nondepressed showed a significant left-bias; those classified as depressed showed a nonsignificant right-bias; mothers who reported experiencing domestic violence also showed a reduced left-bias. The results are interpreted in terms of current theory and research on lateralised hemispheric activation and depression.

Task effects in the development of hand preference in 9‐, 13‐, and 20‐month‐old infant girls

Hand preference for reaching for objects was assessed in 63 female infants (twenty‐two 9‐month‐olds, eighteen 13‐month‐olds, and twenty‐three 20‐month‐olds). Unimanual reaching was elicited for five different kinds of objects after demonstrations of their use: putting pegs in a pegboard, drawing with a crayon, building a tower of cubes, stirring a spoon in a cup, and putting cubes in a cup. Bimanual manipulation was elicited for four different toys after demonstrations of their use: nut‐and‐bolt, car‐in‐a‐jar, ball‐in‐a‐box, and pinwheel. For unimanual reaching, there was a significant increase with age in the percentage of infants showing a right‐hand preference as well as an increase in strength of preference. Further analyses also revealed that of the different tasks, the crayon task was the most reliable predictor of hand preference, whereas the spoon‐in‐the‐cup task was the least reliable. For bimanual manipulation, frequency of right‐hand manipulation increased with age, although there were age‐rela...

Side biases for holding and carrying infants: Reports from the past and possible lessons for today

Most adults hold human infants on the left side, with the infants head to the left of their own body midline. The discovery of this bias is credited to Lee Salk, who first reported it in 1960, but the same was reported at least 300 years earlier and many times again through the early decades of the twentieth century. Along with the left-side reports, however, others named the right as the preferred side. Authors on each side explained the preference and foresaw consequences for the infant: different ones in each case. This article describes the two kinds of reports, asks whether and how they might be reconciled, and discusses their possible lessons for theory and research today.

Dimension preference and performance on a series of concept identification tasks in kindergarten, first-grade, and third-grade children

Data are presented relating childrens preferences for stimulus dimension (form, color, and number) to performance on concept-identification tasks involving preferred and nonpreferred dimensions. The Ss were 77 kindergarten, first-, and third-grade children. As the measure of dimension preference, all Ss sorted cards from the Wisconsin Card Sorting Test. They then performed concept-identification tasks employing the same cards. Seventy-five of the 77 Ss showed significant dimension preferences, 59 Ss preferring form, 9 number, and 7 color. All 59 form-preferring Ss eventually reached criterion for each dimension task. Trials to criterion on each task, however, varied significantly among levels in school and among dimensions. Performance on the concept identification tasks was directly related to level in school. Across levels in school, the form task was most easily solved, color next, and number least. The superiority of third-graders to kindergarteners on the concept identification tasks was apparently not a function of immediate prior experience on the preference test, since the same difference obtained in control kindergarteners and third-graders who received the concept tasks before the preference test. On the number task, however, significantly more control than experimental kindergarteners reached criterion. Furthermore, 47% of the control Ss had significant dimension preferences compared with 97.4% of the experimental Ss. These differences apparently resulted from differences in immediate prior experience.