Multicomponent theory of perception

Summary In a complete identification experiment the three sides of an equilateral triangle were briefly presented as stimuli either singly or in pairs. The resulting 6×6 confusion matrices obtained with three subjects were analyzed according to Rumelhart's (1970, 1971) multicomponent theory of perception (MCTP) in order to test assumptions about feature extraction and decision processes. In agreement with MCTP the detection of a line segment occurring within a pair was stochastically independent of the detection of the other line segment. Two predictions of MCTP were however not confirmed: different line segments are not detected with equal probability, and the probability of detecting a line segment depends on the presence or absence of others. Several decision assumptions of MCTP were tested. The results are the following: If at most one line segment has been detected, then several responses (the candidate set) are compatible with this sensory state. It was argued that response selection from the candidate set is better described by the choice model (Luce, 1959) than by the matching Bayesian rule assumed by MCTP. For a given sensory state the size of the candidate set appears to vary over trials, whereas MCTP assumes it to be constant. In general, the confusion matrices could be predicted quite accurately by MCTP modified according to the above assumptions. However, more accurate predictions were achieved by assuming holistic perceptual processes as well as single feature extraction.This study was supported by a grant from the Universität Konstanz, Forschungsprojekt 32/72 Visuelle Reize, and the experiment to this study was performed in the laboratory of the Arbeitseinheit Mathematische Psychologie im Fachbereich Psychologie/Soziologie der Universität Konstanz.