Abstract
We reported that the speed of judging presence or absence of any difference between memory and test items (any-difference task) stays relatively constant as the number of difference increases. Contrarily, we also found that the speed of judging that of any sameness between memory and test items (any-sameness task) accelerates as the number of sameness increases. To assess the nature of this contrasting difference, the present study let subjects directly compare two sets of four colored boxes that are simultaneously presented across fixation under any-difference and any-sameness manipulation. The RT results showed that increasing the number of difference or sameness between sample and test moderately accelerated speed of subjects' responses in both conditions. These RT patterns were also observed when position matching between the boxes was made easier. There was however a robust pattern of faster RTs in any-different trials with every item being the same across two sets than any-sameness trials with every item being different. The pattern virtually replicates the ‘Fast-same’ effect reported in our previous study. The present results indicate that comparing two perceptual representations may undergo a matching process that is in part similar to the process for comparing VWM representations with perceptual inputs.
NIMH grant R01MH63001, KRF-2009-332-H00027.