Further Evidence for the Representation of Change without Awareness.


Ian M. Thornton1 (ian.thornton@tuebingen.mpg.de) & Diego Fernandez-Duque2

1Max-Planck Institute for Biological Cybernetics, Tuebingen

2University of Toronto


Recently we suggested that studies of change blindness may be telling us more about the limits of explicit reporting/visual awareness than about the limits of visual representation (Fernandez-Duque & Thornton, 2000; Thornton & Fernandez-Duque, 2000). We coupled simple change blindness displays -- in which one rectangle could change orientation -- with two types of implicit secondary tasks: a 2AFC localization paradigm or a speeded orientation priming paradigm. In both cases we found that undetected changes influenced patterns of responses on the secondary tasks. While some researchers have recently begun to question the notion of implicit detection of change (see Mitroff & Simons, OPAM 2000; VSS 2001), here I will present 3 additional lines of evidence to support the claim that the visual system can represent change in the absence of awareness. 1) First, I will review eye movement studies from several labs showing differential gaze patterns when changes go unnoticed. 2) Second, I will present ERP data from our lab (Fernandez-Duque et al., submitted) showing that neural signatures of undetected changes are distinct from those to detected changes or catch trials. 3) Thirdly, I will describe a new behavioral paradigm that is highly robust against contamination from 'strategic' responses, thus providing even stronger evidence for implicit detection of change.