Division and Spreading of Attention across Colour

Abstract

Biological systems must allocate limited perceptual resources to relevant elements in their environment. In vision, this can be achieved by attending to a spatial location or a defining feature (e.g. colour). Spatial attention can be conceived as a spotlight in 2D space, whose focus can differ in breadth and concentration. Could attention to colour also function as a spotlight that highlights an area of colour space? We examined this in an experiment that used multicoloured displays with four overlapping random dot kinematograms (RDKs) that differed only in hue. We manipulated (1) requirement to focus attention to a single colour (red or green) or divide it between two colours (red and green); (2) distances of distractor hues from target hues. This resulted in three different colour contexts, which differed in proximity between targets and distractors. We conducted a behavioural and an electroencephalographic experiment, in which each colour was tagged by a specific flicker frequency and driving its own steady-state visual evoked potential. Behavioural and neural indices of attention showed several major consistencies. Concurrent selection of red and green reduced the efficiency of target enhancement and produced context-dependent distractor interference, consistent with a combination of two hue-selective spotlights of unchanged breadth but reduced concentration. This conceptual similarity in implementation of spatial and feature-based selection implies that attentional modulation of signals in biological systems is likely to be implemented using the same domain-general selective mechanisms, which are well-described with a spotlight metaphor.