Contingent Capture in Visual Search for Conjunctively Defined Targets

During visual search for targets defined by a specific feature, a representation of this feature (an attentional template) is already activated during search preparation. This has been shown in many experiments that used the contingent attentional capture paradigm. Here, we employed this paradigm to investigate the nature of such preparatory target templates during search for conjunctively defined targets. A globally recruited sample of participants searched for targets defined by a single feature (a particular colour, orientation, shape, or size), or by a conjunction of two features from different dimensions. Search displays were preceded by cues with target-matching features, and spatial cueing effects triggered by these cues were measured to test whether a corresponding preparatory search template was active. Contingent attentional capture effects were found for all four dimensions during single-feature search. When targets were defined by a conjunction of colour and either orientation, size, or shape, capture effects were present only for the non-colour dimension, but were consistently absent for colour, suggesting that no preparatory colour templates were activated. In contrast, both shape and size cues triggered reliable and additive contingent capture effects during shape/size conjunction search. These results show that preparatory templates for target features from different dimensions can be activated independently and in parallel during conjunction search, but that colour templates may only be triggered reactively.