Purpose: Two recent studies suggest that explicit measures of change detection may overestimate change blindness. First, when observers reported no explicit awareness of a change, their response latency was still affected by the presence of the change (Williams and Simons 2000). Second, without explicit awareness of a change, the identity of a changed object influenced accuracy in a related judgment task (Thornton and Fernandez-Duque 2000). The current studies explore whether these findings provide evidence for implicit change detection without explicit awareness or whether they could result from explicit processing. Methods: In Experiment 1, observers reported whether or not they believed a display change occurred and then rated their confidence in their response. In Experiment 2, on every trial, observers first performed an orientation judgment task and then noted whether or not they had seen a change. To replicate earlier results, the position of the target of the orientation judgment was spatially linked to the position of the changed item. In our new condition, this spatial link was disrupted. Results: As in earlier studies, observers were quicker to respond 'same' when there was no change than when there was a change. However, they were also quicker to respond when they were more confident, and these differences in confidence accounted for the response time differences when there was or was not a change. In Experiment 2, when the position of the changed item and the target of the perceptual judgment were spatially linked, the identity of the changed item affected the judgment. Yet, no influence remained when the spatial link was de-coupled, suggesting the effect may be due to an explicit search strategy. Conclusion: Our results question the existence of an implicit comparison process that allows for change detection in the absence of explicit processing.
ASJC Scopus subject areas
- Sensory Systems