Factors of hemifield differences in form discrimination.

The influence of some process-limiting variables on hemifield differences for nonsense shapes in a "same-different" classification task was examined. "Different" responses, but not "same," did show systematic effects. Weakly discriminable and unfamiliar shapes which were presented successively yielded a significant left-hemifield advantage, while highly discriminable and more familiar shapes presented simultaneously yielded a nonsignificant right-hemifield advantage. Discriminability, considered independently of the other variables, had effects in opposite directions: low discriminability tended to favor more the right than the left hemifield in each experiment, but the right hemifield more than the left when the comparison was made between experiments. The results are discussed in terms of the spatial-frequency model (Sergent, 1982b, 1983) and the analytic-holistic distinction.