The guidance of spatial attention during visual search for colour combinations and colour configurations

Representations of target-defining features (attentional templates) guide the selection of target objects in visual search. We used behavioural and electrophysiological measures to investigate how such search templates control the allocation of attention in search tasks where targets are defined by the combination of two colours or by a specific spatial configuration of these colours. Target displays were preceded by spatially uninformative cue displays that contained items in one or both target-defining colours. Experiments 1 and 2 demonstrated that, during search for colour combinations, attention is initially allocated independently and in parallel to all objects with target-matching colours, but is then rapidly withdrawn from objects that only have one of the two target colours. In Experiment 3, targets were defined by a particular spatial configuration of two colours, and could be accompanied by nontarget objects with a different configuration of the same colours. Attentional guidance processes were unable to distinguish between these two types of objects. Both attracted attention equally when they appeared in a cue display, and both received parallel focal-attentional processing and were encoded into working memory when they were presented in the same target display. Results demonstrate that attention can be guided simultaneously by multiple features from the same dimension, but that these guidance processes have no access to the spatial-configural properties of target objects. They suggest that attentional templates do not represent target objects in an integrated pictorial fashion, but contain separate representations of target-defining features