George F. Michel

Restricting the field of view: perceptual and performance effects.

Visual perception involves both the high acuity of foveal vision and the wide scope of overlapping peripheral information. The role of peripheral vision in competent performance of the adult visuomotor activities of walking, reaching, and forming a cognitive map of a room was examined using goggles which limited the scope of the normal field of view to 9°, 14°, 22°, or 60°. Each restriction of peripheral field information resulted in some perceptual and performance decrements, with the 9° and 14° restriction producing the most disturbance. In addition, bodily discomfort, dizziness, unsteadiness and disorientation, were reported as the subjects moved around with restricted fields of view.

A meta-analysis of primate hand preferences, particularly for reaching.

P. F. MacNeilage, M. G. Studdert-Kennedy, and B. Lindblom (1987) proposed a progression for handedness in primates that was supposed to account for the evolution of a right bias in human handedness. To test this proposal, the authors performed meta-analyses on 62 studies that provided individual data (representing 31 species: 9 prosimians, 6 New World monkeys, 10 Old World monkeys, 2 lesser apes, and 4 greater apes), of the 118 studies of primate handedness published since 1987. Although evidence of a population-level left-handed bias for prosimians and Old World monkeys supports P. F. MacNeilage et al., the data from apes, New World monkeys, and individual species of prosimians and New World monkeys do not. Something other than primate handedness may have been the evolutionary precursor of the right bias in hand-use distribution among hominids.

RATE VARIABLES AND AUTOMATIZED NAMING IN DEVELOPMENTAL DYSLEXIA

The rate variable in rapid automatized naming (RAN) was investigated in 50 adolescent and 40 adult students with developmental dyslexia, in matched normal controls, and in learning-disabled students without reading difficulties. Visual stimuli depicting familiar colors and common objects were presented in isolation at three film speeds and three exposure times. Film speed and exposure time contributed as independent variables to error rate; and dyslexic subjects of both age groups made significantly more naming errors than controls. Dyslexic subjects also responded with longer naming latencies than controls when the same RAN stimuli were presented in a continuous sequential mode as a matrix of rows and columns. Naming latencies in the sequential presentation were highly correlated with naming errors in the film version. The implications of reduced naming rates for nongraphological stimuli in developmental dyslexia are discussed.

Development of Infant Prehension Handedness: A Longitudinal Analysis During the 6- to 14-month Age Period.

Handedness is a developmental phenomenon that becomes distinctively identifiable during infancy. Although infant hand-use preferences sometimes have been reported as unstable, other evidence demonstrates that infant hand-use preference for apprehending objects can be reliably assessed during the second half of the infants first year of life. The current study provides further insight into the stability of prehension preferences. We modeled individual and group level patterns of prehension handedness during the period from 6 to 14 months of age. We examined the developmental trajectories for prehension handedness in relation to the sampling rate at which preferences are assessed. The results revealed interesting developmental changes in prehension handedness that can only be identified when using monthly sampling intervals. We conclude that using non-linear multilevel models of infant handedness with monthly sampling intervals permit us to accurately capture the developmental changes in manual skills that occur during this period of infancy.

Concordance of Handedness Between Teacher and Student Facilitates Learning Manual Skills

Eighty-six left- and right-handed male and female adults received demonstrations of the manual actions involved in tying three different knots from either left- or right-handed female instructors. Learning was greatly facilitated by concordance of handedness between teacher and student, Sex of subject had no effect, nor were any interaction effects significant. Therefore, it is conceivable that observation learning of manual skill, which accompanied the hominid evolution of tool-use and tool-making skills, could have provided selective pressure for concordance (the right-bias) in human handedness.

Unimanual to bimanual: Tracking the development of handedness from 6 to 24 months

Manual skills change dramatically over the first two years of life, creating an interesting challenge for researchers studying the development of handedness. A vast body of work to date has focused on unimanual skills during the period from the onset of reaching to walking. The current study sought to connect such early unimanual hand use to later role-differentiated bimanual manipulation (RDBM), in which one hand stabilizes the object for the other hands action. We examined hand use in 38 children over 16 monthly visits using a validated measure for assessing hand preference for acquiring objects when children were 6-14 months old. We also developed a new measure for assessing RDBM preference presented when children were 18-24 months old. The new measure reliably elicited RDBM actions in both toddlers and an adult control group (N = 15). Results revealed that some children show preferences for acquiring objects as infants; these preferences are stable and persist into their second year as new skills appear. Moreover, children with no hand preference during infancy shifted to left or right lateralized hand use as toddlers. Despite a higher incidence of left-handedness compared to adult norms, the majority of children were right-handed by 2 years of age.

Bimanual role differentiated toy play during infancy.

Role-differentiated bimanual manipulation requires each hand to perform different, but complementary, actions on one or more objects. It is usually considered to be a late-developing high-level motor and cognitive skill involving the coordination of the two hemispheres of the brain. The frequency of role-differentiated bimanual manipulations was recorded in a longitudinal sample of 24 infants tested at 7, 9, 11, and 13 months during play with 10 different toys. Role differentiation was observed as early as 7 months, and its frequency was unaffected by toy characteristics. Role-differentiated bimanual actions increased with age, and the type of toy did influence the likelihood of eliciting role differentiation between 9 and 13 months.

DO INFANTS EXPRESS DISCRETE EMOTIONS? ADULT JUDGMENTS OF FACIAL, VOCAL, AND BODY ACTIONS

Adult judges were presented with videotape segments showing an infant displaying facial configurations hypothesized to express discomfort/pain, anger, or sadness according to differential emotions theory (Izard, Dougherty, & Hembree, 1983). The segments also included the infants nonfacial behavior and aspects of the situational context. Judges rated the segments using a set of emotion terms or a set of activity terms. Results showed that judges perceived the discomfort/pain and anger segments as involving one or more negative emotions not predicted by differential emotions theory. The sadness segments were perceived as involving relatively little emotion overall. Body activity accompanying the discomfort/pain and anger configurations was judged to be more jerky and active than body activity accompanying the sadness configurations. The sadness segments were accompanied by relatively little body movement overall. The results thus fail to conform to the predictions of differential emotions theory but provide information that may contribute to the development of a theory of infant expressive behavior.

The ontogeny of infant bimanual reaching during the first year

Handedness and pattern of coordination during bimanual reaching were assessed separately for six groups of infants, 7 to 12 months old. Infants reached bimanually for a transparent toy-filled box. On some presentations of the box a low barrier was placed in the path of either the right or left hand, while on other presentations there was no barrier. The youngest and two oldest groups of infants were more likely thon the other age groups to perform simultaneous bimanual reaches with no barrier present, but when a barrier was present the 11.month-olds were most likely to continue to perform simultaneous reaches. This suggests that while infants as young as 7 months perform simultaneous reaches, the organization of these reaches may be different than for older infants. Hand-use preference contributed significantly to selection of a lead hand in non-simultaneous bimanual reaching. The 8-month group, which had the highest proportion of infants with a hand preference, was the only group likely to hit the barrier when it was placed on the nonpreferred side. Hand preference may, thus, bias the use of information about what the environment affords for action.

A lateral bias in the neuropsychological functioning of human infants

Using my published and unpublished research, a description of the development and functional significance of infant hand-use preferences is presented. Although the character of the infants handedness will vary with the development of manual skill, the majority of infants maintain stable preferences throughout the 6- to 14-month age range. As with adult handedness, right-handedness predominates in infancy. Infants without stable hand-use preferences show delays, when compared to infants with stable hand-use preferences, in the development of several sensorimotor cognitive skills. Both maternal- and infant-generated experiences contribute to the development of handedness. Given evidence of limited interhemispheric communication during the 1st year, infant handedness can contribute to the development of the functional specialization of the cerebral hemispheres.