Distinctive shapes benefit short-term memory for colour associations, but not for colour

In four experiments, we examined the effect of pairing colors with either homogeneous or heterogeneous shapes on a short-term memory task. In Experiment 1, we found no differences in color memory for displays in which colors were each associated with different shapes, paired with individual homogeneous shapes, or paired with heterogeneous shapes. In contrast, in Experiment 2, we found that when participants were asked to remember the specific pairings of colors, memory was improved for heterogeneous-shape displays. The benefit for heterogeneous shapes appears to be memorial, rather than one that occurs at the time of encoding (Experiment 3) or retrieval (Experiment 4). The present study suggests that distinctive shapes can be used to help bind color associations in visual short-term memory.