[Properties of distortion of the figures in visual short-term memory]

We investigated the distortion that occurs during the storage of representations in visual short-term memory by using smooth closed figures with varying stimulus complexity and similarity. In similarity judgments, the results suggested that the psychological similarity between two figures was based on averaging physical similarities of matched features. In a detection experiment, the results showed that the processing of detection was limited in its capacity for the precision of shape, and that it was more difficult to detect the precise shape in the case of complex figures. In a recognition experiment, the results showed that forgetting occurred during a one-second retention interval. These two results showed that internal noise distorts both detection and retention processes. These findings suggested that representations of the complex figures with many features were distorted to a larger degree because each feature was individually masked with internal noise. It is concluded that the psychological similarity between an input pattern and a distorted pattern stored in short-term memory is invariant with stimulus complexity.