[Effects of figural complexity and target-distracter similarity on decay rate in short-term visual memory]

We examined the effects of figural complexity and target-distracter similarity on decay rate in short-term visual memory (STVM) for closed contours. The subject's task was to compare two stimuli presented at different points in time. Experiment 1 showed that even a simple pattern with 6 convex parts cannot be handled in STVM for several seconds without loss. Experiments 1 and 2 indicated that decay rate tends to be higher for patterns with higher complexity and for patterns with higher target-distracter similarity regardless of pattern complexity. These results are interpreted that the value of each convex part represented in STVM is an independent Gaussian random variable and that memory noise increases with retention intervals for each convex part separately. Furthermore, they suggest that memory for local features in STVM decays faster. Yet visual rehearsal appears to operate effectively on memorizing even complex patterns. It is concluded that visually presented patterns can be retained in STVM with relatively high fidelity for prolonged periods of time, although some loss of precision occurs inevitably.