Visual search strategies are indexed by event-related lateralizations of the EEG

Two processes have been proposed for picking out information from a visual scene. A parallel process that detects salient features and a following serial process for higher order vision. However, this separation is still under dispute. The current study investigated whether event-related lateralizations (ERLs) of the electroencephalogram are a useful tool to examine these two processes. In a visual search for a colour- or form singleton or a conjunction target, reaction time (RT), P3 amplitudes and ERLs served as dependent variables. RT replicated earlier results for colour and conjunction targets. P3 amplitudes decreased and ERL latencies increased for these conditions. However, form singletons showed RT-, P3- and ERL-results comparable to conjunction targets. ERL-results differed in some conditions from RTs. The results suggest that target attributes alone cannot dissociate between different search strategies but showed that efficient as well as less efficient processes can be utilised for the same targets proposing that processing demands are determined by the inter-relation of target and the distractors.