The contribution of colour to visual memory performance in the non-human primate

Although objects can be identified solely on the basis of information provided by their spatial structure, colour adds another perceptual dimension which may facilitate object identification. Here, we ask whether colour in natural images is associated with improvements in visual memory performance. We degraded coloured and achromatic natural images with increasing amounts of achromatic noise. At a given degradation level, the difference between coloured and achromatic images was thus provided only by the remaining colour. In a delayed matching-to-sample paradigm a sample stimulus at various degradation levels was presented, followed by an undegraded probe stimulus after a delay period. A lever press was required if the sample stimulus matched the probe stimulus. Preliminary results from one monkey show that visual memory performance decreased as a function of noise level for both colour and achromatic conditions. In addition, we found that the recognition performance was significantly higher for the colour condition than the achromatic condition at the same degradation level ( p=0.003, N=14). Since spatial information for both stimulus versions was equally degraded, these results suggest that colour, independently of spatial composition, is associated with an advantage in visual memory performance in the awake behaving primate