Publication Date


Advisor(s) - Committee Chair

Dorsey Grice, Lois Layne, Richard Miller

Degree Program

Department of Psychology

Degree Type

Master of Arts


The present study brought together two lines of research in an attempt to explain some issues in perceptual development. The first pertained to the Mueller-Lyer illusion which tends to decrease with age. Piaaet attributed this change to increased perceptual activities, such as eye movements in the older subjects. Pollack related it to changes in the physical structure of the eye. Grice attributed the charge partially to cognitive processes, and partially to perceptual activities. Second, the concept of iconic memory was reviewed. Grice had employed the concept of iconic memory in an attempt to relate the age related changes in illusions to cognitive changes. He posited that adults are more active in their processing of information from the icon than children. If the use of information in iconic memory could be restricted, differences between children and adults should be reduced. The present study attempted to reduce the use of information from iconic memory in perception of the Mueller-Lyer figure by presenting it simultaneously with an unrelated stimuli and asking subjects to identify the unrelated stimuli before judging line lengths in the Mueller-Lyer figure. It was believed that this process would consume the time available for abstracting information from the icon pertaining to the Mueller-Lyer figure. Three groups of subjects, representing three age levels (children 7-9, intermediate 10-12, and adults) were presented the Mueller-Lyer figure under three viewing conditions. In condition I there were no restrictions on length of time for inspecting the figures. In condition II the figures were shown for only .3 of a second. In condition III the figures were shown for .3 of a second along with two single digits in which the subject was asked to identify the digits before judging the figure. It was hypothesized that condition IT would partially increase the magnitude of the illusion and that condition III would bring a further increase. It was hypothesized that such restrictions would increase the magnitude of illusion for more mature subjects, while having little effect on the younger subjects. The present study confirmed the hypothesis, consistent with the theory that changes in the magnitude of illusion are related to cognitive growth rather than physical structural changes.


Cognition and Perception | Cognitive Psychology | Psychology | Social and Behavioral Sciences