The role of the magnocellular system in implicit cognition

• Main Author: Mansfield, Douglas John
• Other Authors: Tredoux, Colin
• Format: Doctoral Thesis
• Language: English
• Published: University of Cape Town 2015
• Subjects: Psychology
• Online Access: http://hdl.handle.net/11427/12879

Includes bibliographical references. === Implicit cognition paradigms, such as the IAT (Implicit Association Test) are not well understood and are frequently thought to involve ‘unconscious’ attitudes. Although there has been a theoretical shift away from psychoanalytic ideas about consciousness towards more cognitively orientated views, a mystique lingers. The magnocellular (M) system is thought to be involved in rapid but coarse information processing which is a basis for certain kinds of automaticity in information processing, such as reading or visual object recognition. The question this research addressed concerns visual perceptual processes which are not easily controllable and which occur without conscious effort. The role of the M system was investigated in word recognition, object recognition and race feature recognition in a series of experiments. There is evidence that the M system facilitates word recognition in terms of detection accuracy. An experiment involving object recognition replicated the research of Kveraga, et al. (2007b) and similar results were obtained in that when objects were presented under a condition which favoured the M system, recognition accuracy was significantly better and reaction time was significantly shorter than when objects were presented in a condition which favoured the parvocellular (P) system. A series of IAT experiments replicated findings from 1) species, 2) race experiments and similar results were obtained to those reported in the literature. The race IAT experiment was then adapted to use images that were biased towards either the M or P visual systems. As the M system appears to facilitate object recognition, probably by a top-down processing mechanism which may be associated with perceptual automaticity, it was predicted that IAT scores would not be affected in this condition. It was predicted that when images were presented in a condition which inhibited M system functioning, IAT scores would be more neutral (suggesting less response bias). There was a trend which supported this prediction, but the summary score analysis did not show a statistically significant difference.