Diagnostic Colours Influence Speeded Scene Recognition

A critical aspect of early visual processes is to extract shape data for matching against memory representations for recognition. Many theories of recognition assume that this is achieved by luminance information. However, psychophysical studies have revealed that colour is being used by low-level visual modules such as motion, stereopsis, texture, and 2-D shapes. Should colour really be discarded from theories of recognition? Here we present two studies which seek to throw light on the role of chromatic information for the recognition of real scene pictures. We used three versions of scene pictures (gray levels, normally coloured and abnormally coloured) coming from two broad categories. In the first category, colour was diagnostic of the category (eg beach, forest, and valley). In the second category colour was not diagnostic (eg city, road, and room). In the second category colour was not diagnostic (eg city, road, and room). Results revealed that chromatic information is being registered and facilitates recognition even after a 30 ms exposure to the scene stimuli. However, influences of colour on speeded categorisations were only observed with the colour-diagnostic categories. No influence of colour was observed with the other categories. A similar pattern of results was observed with 120 ms exposure. However, there was an interference of the wrong colour on recognition in colour-diagnostic categories. In sum, colour, when it is diagnostic of the category, influences speeded scene recognition.