A compressibility account of the color-sharing bonus in working memory

It has been established that objects sharing color in a visual display can boost working memory. The capacity to encode singletons particularly benefits from the repetition of colors encoded as perceptual groups. We manipulated the algorithmic complexity of visual displays to test whether compressibility of information could account for the color-sharing bonus. This study used a free recall working memory task in which the participants were shown displays of 2 to 8 color items. We examined the influence of set size, complexity, number of same-color clusters and amount of color redundancy. The results showed that the probability of correct recall of the pattern and the proportion of similarity between the pattern and the response decreased with an increase of each manipulated variable, except for color redundancy in terms of probability of correct recall. The model performance of complexity did not differ from that of clusters, but complexity was found more accurate than either set size or color redundancy. The results also showed that similar items were more often recalled adjacently, and complexity correlated strongly with the number of extra color repetitions in the response, suggesting that more complex patterns encouraged the use of information compression. Moreover, color repetitions were more often recalled first and the probability of correct recall for singletons and sub-patterns could be predicted by the compressibility measure. We discuss the potential advantage of using compressibility measures to capture the effects of regularities in visual patterns, in particular to refine analysis of the color-sharing bonus.