Experimental Psychology Seminar - Where does Visual crowding take place

Speaker: Dr Ramakrishna Chakravarthi, School of Psychology, University of Aberdeen

Visual crowding is the phenomenon where an otherwise identifiable object is rendered unidentifiable by the presence of nearby flankers. It offers a window into the mechanisms of object recognition. Traditional explanations of crowding propose that it is a bottom-up phenomenon, wherein the features of neighbouring objects are jumbled or averaged together, leading to the inability to identify the target. However, recent findings suggest that a) such intermingling of features occur at multiple levels of the visual hierarchy and/or b) top-down processes are involved in visual crowding. In a series of three studies, we examined if this was the case. We tested if, once low-level features were controlled for, whether the ‘higher-level’ effects in crowding would persist. We found that almost all (although not all) of the higher-level effects that we examined were eliminated by carefully controlling low-level features. These findings suggest that a) higher-level effects in crowding are rare and b) considerable caution needs to be exercised before such effects are claimed. We conclude that most, if not all, of crowding, and hence the construction of an object’s representation, occurs at a low-to-mid level of the visual processing hierarchy.

Time: 4pm, Tuesday 11th  October 2016

Venue: Room 305, 26 Bedford Way (WC1H 0AP)