Consistency of hand-preference across the early years: long-term relationship to verbal intelligence and reading achievement in girls

The relationship between consistency of hand preference, left hemispheric specialization, and cognitive functioning was examined in an ongoing longitudinal investigation. Children were classified as consistent or inconsistent in their hand preference across 5 assessments from ages 18 to 42 months. Findings demonstrated that (a) this early classification continued to reveal differences in cognitive functioning from 10 to 17 years but only for girls, (b) consistent girls' performances were continually higher relative to the inconsistent girls on measures of verbal intelligence and reading achievement, (c) differences between the female groups were specifically related to left-hemispheric language specialization, and (d) one factor influencing the consistent girls' development may be the amount of reading exposure received during infancy.     

Effects of handedness and sex on the morphology of the corpus callosum: a study with brain magnetic resonance imaging.

In view of conflicting data in the existing literature, we examined 53 normal subjects using a handedness questionnaire and callosal area measurements obtained from midsagittal MRI images. The callosum was found to be significantly larger in nonconsistent right-handers (NCRH), especially in its anterior half and especially for males. A significant hand x sex interaction, favoring consistent right-handed (CRH) females, was also found for the posterior midbody, a region known to house interhemispheric fibers connecting the right and left posterior association cortices. These results (1) confirm Witelson's (1985) first findings on postmortem specimens; (2) validate a dichotomy between CRH and NCRH rather than simply considering the writing hand, as was the case in most other similar studies; and (3) suggest that at least two different sex-related--probably hormonal--factors may be acting during the callosal development, one explaining the larger anterior half in NCRH males and the other the larger posterior midbody in CRH females.     

The influence of a hand preference for acquiring objects on the development of a hand preference for unimanual manipulation from 6 to 14 months

Development of hand preferences for unimanual manipulation of objects was explored in 90 infants (57 males) tested monthly from 6 to 14 months. From a larger sample of 380 infants, 30 infants with a consistent left hand preference for acquiring objects were matched for sex and development of locomotion skills with 30 infants with a consistent right hand preference for acquisition and 30 with no preference. Although frequency of unimanual manipulations increased during 6–14 month period, infants with a hand preference for acquisition did more object manipulations than those without a preference for acquisition. Multilevel modeling of unimanual manipulation trajectories for the three hand-preference groups revealed that hand preferences for unimanual manipulation become more distinctive with age, and the preference is predicted by the hand preference for object acquisition. Infants with a right and left hand preference for object acquisition develop a right and left (respectively) hand preference for unimanual manipulation. However, the majority of infants at each month do not exhibit hand preferences for unimanual manipulation that are unlikely to occur by chance, even by 14 months. The results are consistent with a cascading theory of handedness development in which early preferences (i.e., for acquisition) are transferred to later developing preferences (i.e., for unimanual manipulation).     

Longitudinal relations between children's exposure to TV violence and their aggressive and violent behavior in young adulthood: 1977-1992

Although the relation between TV-violence viewing and aggression in childhood has been clearly demonstrated, only a few studies have examined this relation from childhood to adulthood, and these studies of children growing up in the 1960s reported significant relations only for boys. The current study examines the longitudinal relations between TV-violence viewing at ages 6 to 10 and adult aggressive behavior about 15 years later for a sample growing up in the 1970s and 1980s. Follow-up archival data (N = 450) and interview data (N = 329) reveal that childhood exposure to media violence predicts young adult aggressive behavior for both males and females. Identification with aggressive TV characters and perceived realism of TV violence also predict later aggression. These relations persist even when the effects of socioeconomic status, intellectual ability, and a variety of parenting factors are controlled.     

The use of bouts and frequencies in the evaluation of hand preferences for a coordinated bimanual task in chimpanzees (Pan troglodytes): an empirical study comparing two different indices of laterality

Hand preferences for a coordinated bimanual task were assessed in 109 chimpanzees (Pan troglodytes). Hand preference was evaluated for 4 test sessions using bouts and frequencies of hand use to compare the sensitivity of each level of analysis in evaluating individual variation in handedness. Overall, significant population-level right-handedness was found using several different measures of hand use. Handedness indices based on bouts and frequencies were highly and significantly correlated. Moreover, hand preferences were consistent across tests despite efforts to situationally bias preference during each test. Taken together, these data do not support the view that bouts are a better level of analysis for evaluating hand preference. The results further suggest that hand preferences for coordinated bimanual actions are not influenced by situational factors and may reflect an inherent specialization of the left hemisphere for motor skill.     

Drawing and handedness of preschoolers: a repeated-measurement approach to hand preference

This study investigated handedness and drawing by preschoolers. An observational method for repeated measurement of hand preference is presented. A sample of 381 children (191 girls, 190 boys) ranging in age from 48 to 71 mo. was tested for drawing and hand preference on 14 tasks. Consistent hand preference was defined as always using a particular hand (left or right) for the same task. Girls with consistent hand preference showed better drawing scores compared to girls with inconsistent hand preference. The results showed the importance of a reliable method for measuring hand preference within a single task as early as preschool age.     

The Westermarck Effect and early childhood co‐socialization: Sex differences in inbreeding‐avoidance

The aim of this study was to determine whether there are sex differences in regard to the effect of early childhood co‐socialization on inbreeding‐avoidance at sexual maturity. Multiple logistic regression methodology was used to model the relationship between cousin relationship and social proximity in childhood and its effect on mate choice beyond adolescence for a sample of Moroccan participants. Females showed a synergistic interaction effect for cousin marriage and childhood co‐socialization and an additional interaction effect for co‐socialization during the first seven years of childhood. Male participants showed no significant effect for early childhood co‐socialization. The Westermarck Effect hypothesis that early childhood co‐socialization leads to a lack of sexual interest at maturity is thus supported for female participants but not for male participants. These results are consistent with expectations from parental investment theory that females should show greater inbreeding‐avoidance than males do because of the greater costs females suffer as a consequence of inbreeding depression.     

Impact of Handedness Consistency on Bimanual and Unimanual Continuous Movements

Bimanual coordination is an essential human function requiring efficient interhemispheric communication to produce coordinated movements. Previous research suggests a “bimanual advantage” phenomenon, where completing synchronized bimanual tasks results in less variability than unimanual tasks. Additionally, of hand dominance has been shown to influence coordinated performance. The present study examined the bimanual advantage in individuals with consistent and inconsistent handedness. It was predicted that participants with consistent handedness would not display a bimanual advantage unlike those with inconsistent handedness. Fifty-six young adults completed a finger-tapping paradigm in five conditions: unimanual tapping with either left or right hand, in-phase bimanual tapping, and out-of phase bimanual tapping led by either left or right hand. Results were not consistent with the hypothesis that participants with consistent handedness displayed the “bimanual advantage”. However, the “bimanual advantage” was not evident for the inconsistent handers when the temporal consistency was measured with either the left or right hand only. Overall, the “bimanual advantage” may be dependent upon consistency of hand preference, as well as the direction of hand dominance.     

Relationships of criminality and psychopathy with eight other apparent behavioral manifestations of sub-optimal arousal

The application of arousal theory to the study of criminality and psychopathy leads one to hypothesize that any behavior reflecting sub-optimal arousal should be more common among criminals and psychopaths than among their counterparts. In the present literature review, consistent support was found for this hypothesis by indicating the existence of substantial associations between criminality/psychopathy and the following eight behavior patterns: (1) resistance to punishment, (2) poor academic performance,or performance below intellectual potential, (3) impulsiveness, or minimal persistence at task assigned and coordinated by others, (4) childhood hyperactivity, (5) risk taking and sensation seeking, (6) recreation drug use, (7) preference for active social interactions, and (8) preference for broad-ranging sexual experiences and unstable pair bonding tendencies. Also consistent with arousal theory were numerous studies indicating that these eight behavior patterns were intercorrelated with one another. The conclusion suggested by this review was that criminality and psychopathy exists as part of a multi-variable cluster of behavior patterns which is a manifestation of sub-optimal arousal.     

Intellectual functioning and aggression

In a 22-year study, data were collected on aggressiveness and intellectual functioning in more than 600 subjects, their parents, and their children. Both aggression and intellectual functioning are reasonably stable in a subject's lifetime and perpetuate themselves across generations and within marriage pairs. Aggression in childhood was shown to interfere with the development of intellectual functioning and to be predictive of poorer intellectual achievement as an adult. Early IQ was related to early subject aggression but did not predict changes in aggression after age 8. On the other hand, differences between early IQ and intellectual achievement in middle adulthood were predictable from early aggressive behavior. A dual-process model was offered to explain the relation between intellectual functioning and aggressive behavior. We hypothesized that low intelligence makes the learning of aggressive responses more likely at an early age, and this aggressive behavior makes continued intellectual development more difficult.     

Socioeconomic status and executive function: developmental trajectories and mediation

Childhood socioeconomic status (SES) predicts executive function (EF), but fundamental aspects of this relation remain unknown: the developmental course of the SES disparity, its continued sensitivity to SES changes during that course, and the features of childhood experience responsible for the SES–EF relation. Regarding course, early disparities would be expected to grow during development if caused by accumulating stressors at a given constant level of SES. Alternatively, they would narrow if schooling partly compensates for the effects of earlier deprivation, allowing lower‐SES children to ‘catch up’. The potential for later childhood SES change to affect EF is also unknown. Regarding mediating factors, previous analyses produced mixed answers, possibly due to correlation amongst candidate mediators. We address these issues with measures of SES, working memory and planning, along with multiple candidate mediators, from the NICHD Study of Early Childcare (n = 1009). Early family income‐to‐needs and maternal education predicted planning by first grade, and income‐to‐needs predicted working memory performance at 54 months. Effects of early SES remained consistent through middle childhood, indicating that the relation between early indicators of SES and EF emerges in childhood and persists without narrowing or widening across early and middle childhood. Changes in family income‐to‐needs were associated with significant changes in planning and trend‐level changes in working memory. Mediation analyses supported the role of early childhood home characteristics in explaining the association between SES and EF, while early childhood maternal sensitivity was specifically implicated in the association between maternal education and planning. Early emerging and persistent SES‐related differences in EF, partially explained by characteristics of the home and family environment, are thus a potential source of socioeconomic disparities in achievement and health across development.     

Evidence for a gene-environment interaction in predicting behavioral inhibition in middle childhood

Gene-environment interactions are presumed to shape human behavior during early development. However, no human research has demonstrated that such interactions lead to stable individual differences in fear responses. We tested this possibility by focusing on a polymorphism in the promoter region of the gene for the serotonin transporter (5-HTT). This polymorphism has been linked to many indices of serotonin activity. Specifically, we tested the hypothesis that an interaction between children's 5-HTT status and maternal reports of social support predicts inhibited behavior with unfamiliar peers in middle childhood. Results were consistent with this hypothesis: Children with the combination of the short 5-HTT allele and low social support had increased risk for behavioral inhibition in middle childhood.     

Hand preference in the use and manufacture of tools by tufted capuchin (Cebus apella) and lion-tailed macaque (Macaca silenus) monkeys.

The purpose of this study was to examine hand preference in the use and manufacture of probing tools by tufted capuchin and lion-tailed macaque monkeys (Cebus apella and Macaca silenus). Hand preference for the tool-using sequence was noted in 4 of 5 capuchins (a left-hand preference was noted in 3 ss) and 3 of 4 macaques (a left-hand preference was noted in 2 ss). The monkeys frequently used bimanual action in the initial and final segments of the 3-component task and typically modified tools through coordinated action of the hands and teeth. These data provide evidence consistent with the hypotheses that (a) hemisphere specialization for manual control evolved in primates prior to intensive use of tools by early hominids and (b) monkeys prefer the left hand for precise, visually guided, manipulative actions.     

Development of handedness: comparison of questionnaire and performance-based measures of preference

Hand preference has been assessed primarily using questionnaires. This approach is difficult to use with children so researchers have frequently used observation of hand choice when children pick up and use tools. Recently we developed such a performance-based measure, the WatHand Box Test (WBT). Participants ranging in age from 2 to 24 years each completed the WBT and the Revised Waterloo Handedness Questionnaire. Analyses revealed a strong preference for the right hand across all age groups on both tests with no significant differences across age and a significant correlation between the two measures. These findings do not concur with other work showing children younger than six years exhibited a much smaller right-hand preference. The concordance between these two preference measures is consistent with our previous findings. However, the relatively small common variance explained in this relationship suggests that these two tests may reflect somewhat different components of preference.     

Sexual experience and preference for males or females in the female rat

The influence of sexual experience on preference behavior was investigated in adult female rats. In the first experiment, preference behavior for sexually active males versus estrous females was investigated in female rats who were experienced with mounting behavior. Preference of these mount experienced females was compared to preference of females who were naive in this respect. Mount experience with estrous females induced a female-directed preference in ovariectomized female rats, irrespective of whether the females were treated with OIL or with testosterone-propionate (500 micrograms TP, injected once 48 h prior to testing). Sexually naive, OIL-treated females did not show a preference for males or females, but TP induced a preference for a male. Individual differences in mount frequency were not correlated with preference behavior. In the second experiment, the influence of experience with feminine sexual responses on preference behavior was investigated. OIL-treated and TP-treated females oriented equally toward males and females when they had been given the opportunity to copulate with males prior to the preference tests. The results strongly suggest that prior sexual experience is an important determinant of preference behavior. The female's behavior during sexual interactions was, however, not predictive of later preference.     

Pathways of peer relationships from childhood to young adulthood

This study examined trajectories of peer social preference during childhood and personality assessed in early adolescence in relation to trajectories of friendship quality during early adulthood. Participants (N = 585) were followed from ages 5 to age 23. At ages 5 to 8, peers provided sociometric nominations; at age 12 participants reported their own personality characteristics; from ages 19 to 23 participants rated their friendship quality. Latent growth modeling revealed that trajectories characterized by high levels of childhood peer social preference were related to trajectories characterized by high levels of early adulthood friendship quality. Early adolescent personality characterized by extraversion and conscientiousness predicted higher friendship quality at age 19, and conscientiousness predicted change in friendship quality from ages 19 to 23. This study demonstrates that peer relationships show continuity from childhood to early adulthood and that qualities of core personality are linked to the development of adult friendships.     

Cultural influences on preference consistency: Consistency at the individual and collective levels

Previous research has shown that there are cultural differences in self-concept consistency across situations. However, little is known about cultural differences in preference consistency over time. The present research examined whether Americans are more consistent in their preferences over time than are Japanese. As hypothesized, there were cultural differences in self-reported ( and ) and actual ( and ) preference consistency over time. Further, cultural differences in preference consistency at the individual level (Study 1) were found to aggregate into collective level differences ( and ) in the consistency of preference trends, such as the popularity of baby names. Implications and future directions are discussed.     

Interaction between lateralized systems: exploring the complexity of laterality

To assess the extent of interaction between lateral biases in response systems at different levels of the neuraxis and detect the possible presence of different patterns of interaction related to population subgroups, we investigated laterality in hand reaching, whole-body turning and eye use in 20 bushbabies (Otolemur garnettii). Two subgroups were clearly identified: the STABLE group was composed of subjects, mainly females, that were consistent in hand preference and had correlation of hand/eye bias; the UNSTABLE group included subjects, mainly males, that showed instability in hand preference as a function of change in test conditions and had correlation of hand/turning bias. Results are interpreted to support the value of the study of interaction between lateral biases as a way of gaining a deeper understanding of the complexity of laterality.     

Interaction of sex-related psychological characteristics and psychoneuroendocrine stress responses

Sex-related psychological characteristics of male and female engineering students were examined and correlated with measures of sympathetic-adrenal medullary hormones. Self-ratings showed that both males and females perceived themselves as equally high in characteristics generally viewed as masculine and feminine. Retrospective reports of play activities in childhood reflected the traditional sex-role patterns, whereas ratings of adult interests, hobbies, and job preferences showed that the two gender groups had moved in a more androgynous direction, with the increase in females' cross-sex interests being greater than that of males. The intellectual performance profiles showed the well-documented sex difference, with males excelling in visuospatial abilities and females in verabl abilities and perceptual speed. Correlations between measures of intellectual performance and catecholamine excretion were mainly positive in the male group and negative in the female group, which is consistent with findings from previous studies.     

Comparison of arousal and preference assessment outcomes for sex offenders with intellectual disabilities

We compared outcomes of arousal and preference assessments for five adult male alleged sexual offenders with intellectual disabilities. Arousal assessments involved the use of the penile plethysmograph to measure changes in penile circumference to both deviant (males and females under the age of 18) and nondeviant (males and females over the age of 18) video clips. Paired‐stimulus preference assessments were arranged to present still images from the video clips used in the arousal assessments. Results showed correspondence between the assessments for four out of the five participants. Implications are discussed for the use of preference assessment methodology as a less intrusive assessment approach for sexual offender assessments.