Visual working memory for natural scenes: the effect of chromatic, luminance and spatial frequency content

Long-term memory for images of natural scenes is known to be very good. However visual working memory (VWM) for natural scene stimuli is less well understood. We investigated VWM for natural scene stimuli by measuring VWM performance as a function of both encoding time and cognitive load level, employing a method that approximates everyday natural vision. VWM performance was compared between (a) scenes containing either full chromatic and luminance information, (b) luminance-only (isochromatic) information and (c) chromatic-only (isoluminant) information. VWM performance was also measured for scenes in which the scene’s structure had been destroyed by Fourier phase scrambling, or following removal of either the high or low spatial frequencies. It was found that recall ability for isoluminance scenes was relatively poor, as it was also for the phase scrambled scenes with high cognitive load or short encoding time. However, recall ability was similar for the full colour (i.e., chromatic and luminance information combined) and luminance-only scenes, except for very brief presentation times where performance for the luminance-only scenes was worse. These findings suggest that spatial scene structure is important for good VWM performance, and for very brief presentations there is a particular reliance on chromatic information.