The role of similarity in updating numerical information in working memory: decomposing the numerical distance effect

The present study investigates the process of updating representations in working memory (WM) and how similarity between the information involved influences this process. In WM updating tasks, the similarity in terms of numerical distance between the number to be substituted and the new one facilitates the updating process. We aimed to disentangle the possible effect of two dimensions of similarity that may contribute to this numerical effect: numerical distance itself and common digits shared between the numbers involved. Three experiments were conducted in which different ranges of distances and the coincidence between the digits of the two numbers involved in updating were manipulated. Results showed that the two dimensions of similarity had an effect on updating times. The greater the similarity between the information maintained in memory and the new information that substituted it, the faster the updating. This is consistent both with the idea of distributed representations based on features, and with a selective updating process based on a feature overwriting mechanism. Thus, updating in WM can be understood as a selective substitution process influenced by similarity in which only certain parts of the representation stored in memory are changed.