Abstract
When changes in visual scenes occur after a brief visual disruption, observers remarkably often fail to detect even large changes. This so- called change blindness has often been interpreted as a result of impoverished visual information encoding or as a failure to compare the pre-change and post-change scene. In the present electroencephalography study, we investigated whether pre-change and post-change information can be compared unconsciously, even when observers are unaware that a change has occurred. If so, this would suggest that change blindness does not preclude high-level, semantic object processing. We presented scenes composed of natural objects in a change blindness paradigm in which one object changed from one presentation to the next. Object changes were either semantically related (e.g. rail car changed to rail) or unrelated (e.g. rail car changed to sausage). Observers were first asked to detect whether any change had occurred and then to judge the semantic relation of the two objects involved in the change. For semantically incongruent changes, we found an N400-like event-related potential (ERP) effect, i.e. a more negative-going ERP for semantically unrelated changes. Importantly, the N400 effect persisted even when observers were unaware of the change, rendering them unable to report the semantic relationship of pre-change and post-change object. The presence of a neuronal marker of semantic processing implies that even under change blindness, the identities of pre-change and post-change object are encoded and even processed up to the stage where their semantic relationship is computed. This finding suggests that 1) change blindness does not necessarily imply sparse visual representations, and 2) change blindness does not necessarily reflect a comparison failure of the pre-change and post-change scene. In sum, the encoding and processing of visual information under change blindness is by far less impoverished as previously believed.
Meeting abstract presented at VSS 2014