Detection of parts in patterns and images.

Subjects performed in an embedded-figures detection task which required them to judge whether one pattern was a part of another. In the perception condition, the part was presented before the complete pattern, but in the imagery condition, the part was presented after the complete pattern. Subjects made fast, but inaccurate, responses in the perception task when RT s were recorded, but the error rate declined substantially when they were given 10 sec to make a decision. In the latter condition, subjects failed to detect a part on 14% of the trials in the perception condition and on 72% of the trials in the imagery condition when a correction was made for prior perception of the part. A subsequent experiment showed that the high error rate in the imagery task was not the result of the subject's inability to remember the complete pattern. The complexity of mental operations and the limited accuracy of visual images are considered as possible alternative explanations of the results.