Processing Unattended Visual Information: Insights From an Analysis of Repetition Priming Using Event-Related Brain Potentials

197 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1997.Two unresolved issues in the attention and memory literature concern the extent and nature of the processing of unattended visual information. In an earlier study, it was found that when individuals make lexical decisions about one of two simultaneously presented, visual letter strings, a modulation of event-related potentials (ERPs) may be observed when the unattended word is repeated on the subsequent trial as the unattended word. This modulation differs in polarity and scalp distribution from that typically seen when attended words are repeated. In seven experiments, it is established that the ERP modulation for repeated unattended words (a) is reliable and attributable to the repeated unattended words rather than to accompanying attended words, (b) can occur for words repeated in a different location and in a different font, (c) is associated with faster lexical decision responses, (d) is not related to the mechanism that underlies the slowing in reaction times to recently ignored targets (negative priming), (e) can occur for digits as well as words, and (f) is related to ease of selection. The occurrence of this ERP modulation suggests that the processing of unattended information can extend beyond elementary physical features (to involve orthographic identity in the case of words). This processing leaves a representation in memory which can influence subsequent processing for at least 3 s. The qualitative differences between the ERP modulations for repeated unattended and repeated attended information suggest that repeated unattended information is processed in a qualitatively different manner than repeated attended information. Repeated unattended information appears to benefit from an inhibitory mechanism sometimes applied to unattended information to enable selective processing. The inhibited representation may carry forward in time, making subsequent selections easier when the same item is again irrelevant.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD