title: Negative and positive congruence effects in letters and shapes.
abstract: In six experiments in which a binary classification task was used, letter and nonletter (geometrical shapes, pseudoletters, or rotated letters) targets were presented either in isolation or surrounded by a geometrical shape. The surrounding shape could be congruent or incongruent with the target. When the classification required a distinction between letters and nonletters, either explicitly (Experiments 1-3) or implicitly (Experiment 4), a negative congruence effect was obtained for letters, contrasting with a regular, positive congruence effect for nonletters. When no distinction was to be made, letters and nonletters invariably showed a positive congruence effect (Experiments 5 and 6). In particular, between Experiments 1-4 and Experiments 5 and 6, the occurrence of negative or positive congruence effects for the same stimuli depended on the task. Feature interaction, target selection, and response competition explanations were tested against a feature integration approach. The results are explained in terms of different feature integration strategies for letters and nonletters.
authors.affiliation: Laboratory for Perceptual Dynamics, Brain Science Institute, RIKEN, Wako-Shi, Saitama, Japan. ceesvl@brain.riken.go.jp
authors.forename: Cees
authors.initials: C
authors.lastname: van Leeuwen
authors.forename: Thomas
authors.initials: T
authors.lastname: Lachmann
mesh_terms: D000328:Adult; D005260:Female; D005403:Fixation, Ocular; D005556:Form Perception; D006801:Humans; D008297:Male; D011930:Reaction Time