About this Research Topic
Comparing hand preference across manual functions, species and age, is one way to understand the evolution of handedness. Although non-human primates, and to a certain extent other vertebrates (Andrew & Rogers, 2002), show limb preference at the population level on a narrow range of tasks (for review, see Hopkins, 1993), only humans show a consistent pattern of hand preference across a large range of tasks at the population level.
In humans, as in non-human primates, the degree of preference for one hand varies between functions: for instance, handedness appears to be stronger for symbolic than for object related activities. Very comparable results have been obtained for human infants and for non-human primates as well. Handedness is stronger for bimanual than for unimanual simple actions, at least when each hand carries out a complementary action, though not when actions are more similar for each hand. The use of the left hand for support shows that the direction of preference varies across functions, the left hand being preferred for support or for spatial localization, whereas the right hand is preferred, by the majority of individuals, for actions requiring precision.
One function for which hand preference has been observed very early during development is the haptic function. Some evidence shows that the hands may be specialized in detecting perceptual characteristics of stimuli such as its global and analytic characteristics early in infancy. Studies in haptics come mostly from human subjects, even though there are some animal studies of haptic asymmetries . An interesting phenomenon is that, in contrast to other senses, motor skills play a major role in haptics for both executing an action and using the hand as a sensory device to scan a surface. Studies in haptics have shown that the hands do not differ in perceptual tasks that require comparisons between three dimensional stimuli, curvature perception, estimating distances or tactile numerosity . Studies examining proprioception in the absence of vision demonstrated that the congenitally blind and sighted blindfolded children were able to point at targets on a touch screen, with their left and right hands, both after immediate and delayed instructions, indicating that the hands may not differ in ability, and proprioception is not dependent on vision.
The developmental origin of handedness is a subject of debate. A right-hand preference for body touching in utero (Hepper, McCartney, & Shannon, 1998), seemed to predict future hand preference (Hepper, Wells, & Lynch, 2005). The age at which lateralization occurs is yet inconclusive. Some authors agree that the majority of infants develop hand preference by the end of the first year, whereas others emphasize fluctuations of hand preference in the first two years during development .
The purpose of the proposal is to welcome specialists of hand preference across species (humans and non-humans), functions (precision grasping and manipulation, localization, symbolic, haptic, etc.), and age groups (infants, children, and adults) to share their present research interests.
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