The temporal dynamics of visual search: Evidence for parallel processing in feature and conjunction searches

Feature and conjunction searches have been argued to delineate parallel and serial operations in visual processing. The authors evaluated this claim b y examining the temporal dynamics of the detection of features and conjunct ions. The Ist experiment used a reaction time (RT) task to replicate standa rd mean RT patterns and to examine the shapes of the RT distributions. The 2nd experiment used the response-signal speed-accuracy trade-off (SAT) proc edure to measure discrimination (asymptotic detection accuracy) and detecti on speed (processing dynamics). Set size affected discrimination in both fe ature and conjunction searches but affected detection speed only in the lat ter. Fits of models to the SAT data that included a serial component overpr edicted the magnitude of the observed dynamics differences. The authors con cluded that both features and conjunctions are detected in parallel. Implic ations for the role of attention in visual processing are discussed.