The goal of this study was to examine the relations between three different measures of handedness: unimanual reaching, bimanual manipulation and unimanual manipulation. The appropriateness of the task chosen to evaluate handedness was also explored by contrasting different bimanual manipulation tasks for the more or less differentiated (passiveaactive) roles assigned to each hand. Forty children, between 18 and 36 months of age, were tested in the three conditions. The results show that the degree of bimanual handedness is greater on the bimanual tasks with a strong role differentiation than on the tasks with less differentiation. Bimanual tasks with a strong role differentiation elicited more righthandedness than unimanual reaching. Among the children who showed handedness in reaching, the correlation between unimanual and bimanual handedness was high, especially for right-handers. For some tasks, bimanual handedness appeared at the earliest age studied here (18 months), and there was little relationship between bimanual handedness and bimanual skill. In contrast with unimanual reaching, there was no age-related change in the degree of handedness for either bimanual or unimanual manipulation. There was a bias toward the use of the right hand for unimanual manipulation. It was concluded that grasping is not the best task to employ to look for robust evidence of handedness, and that bimanual tasks offer a better way to estimate handedness in children, as long as the tasks are carefully chosen.

The goal of this study was to evaluate the relationship between object-related handedness and handedness for communicative gestures. We observed 22 infants aged 14 months on a baby laterality test consisting of grasping objects in different conditions, on a pointing task with targets placed out of reach at different spatial positions from left to right, and on word understanding and word production. Results show that 77% of infants pointed to the left, middle, and right targets. The majority of infants were right-handed for pointing--except for the far left target--and, to a lesser extent, for grasping objects, but there was no significant relation between the two measures of handedness. The frequency of pointing tended to be related to the number of words understood, and infants right-handed for pointing understood and produced significantly more words than non-right-handed pointers. These results are interpreted as confirming the link between pointing and language development, and as showing that communicative gesture lateralisation is not a mere consequence of object-related handedness, at least during development. Whether lateralised communicative gesture reinforces a pre-existing tendency to use the right hand to interact with objects remains an open question.

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