3.2 Article 3
Early signs of visual categorization for biological and non-biological stimuli in humans
Yolande Mouchetant-Rostaing, CA Marie-HeÂle Áne Giard, Claude Delpuech, Jean-FrancÂois Echallier and Jacques Pernier
INSERM-U280, 151, Cours Albert Thomas, 69424 Lyon Cedex 03, France
Corresponding Author Received 26 April 2000, accepted 30 May 2000

In a previous experiment aimed at studying gender processing from faces, we had found unexpected early ERP differences (45±85 ms) in task-irrelevant stimuli between a condition in which the stimuli of each gender were delivered in separate runs, and a condition in which the stimuli of both genders were mixed. Similar effects were observed with hand stimuli. These early ERP differences were tentatively related to incidental categorization processes between male and female stimuli. The present study was designed to test the robustness of these early effects for faces, and to examine whether similar effects can also be generated between two classes of non-biological stimuli. We replicated the previous ®ndings for faces, and found similar early differential effects (50±65 ms) for non-biological stimuli (grey and hatched geometrical shapes) only, however, when the two shape categories were separated by conspicuous visual characteristics. While these results can partly be explained by phenomena related to neuronal habituation in the visual cortex, they may also suggest the existence of coarse and automatic categorization processes for rapid distinction between two wide classes of stimuli with strong psychosocial significance for humans. NeuroReport 11:2521± 2525 © 2000 Lippincott Williams & Wilkins.

Key words: Biological stimuli; Event-related potential (ERP); Geometrical shapes; Human faces; Humans; Rapid visualv categorization