Activation and inhibition of stimulus features in conjunction search.

Two visual search experiments were conducted to examine how activation of target-relevant features and inhibition of target-irrelevant features are involved in conjunction search. The hypothesis was that if an excitatory mechanism is involved, it should be revealed as facilitation when a target and distractors are repeated in two successive displays. If an inhibitory mechanism is involved, suppression should be obtained when distractor features from one display determine the target in the following display. The results of Experiment 1 showed that facilitation was observed consistently across two set sizes (5 and 9), whereas suppression was obtained only with larger set size (9). This pattern of results was replicated and extended in Experiment 2 with different set size. It seems that both excitatory and inhibitory mechanisms are involved in conjunction search. The excitatory mechanism seems to play a role in conjunction search regardless of search difficulty, whereas the inhibitory mechanism might play a role only when set size is larger.