Stereographic information aids in distinguishing spatial relationships, however, if the stereo object is ambiguous, spatial distortions occur. The Necker Cube (see fig. 1) is a visual illusion where a three-dimensional line drawing of a cube appears to flip in space. The Necker Cube was discovered in 1832 by a Swiss crystallographer, Louis Albert Necker (link to source) It may appear to be projecting forward, toward the viewer, or moving back in space. Some researchers have looked for age differences in ability to see the cube "flip" (Beer, Beer, Markley and Camp 1989). However, most recent research on the cube attempts to uncover the mechanism that causes a shift in views. A study by Wallace (1986) suggests that selective attention or concentration does have an effect on reversal rates of the Necker Cube. Attention was manipulated by instructing subjects to mentally perform addition problems while observing the cube. The current study examines how attention or concentration effects the reversal rate.
Methods
Subjects: The subjects consisted of 24 volunteer undergraduate students from Alma College, Alma, MI.
Apparatus: The study was conducted on a Macintosh G3 computer using Eyelines software designed by Dr. Beagley at the psychology department at Alma College. Results were saved in this program and later analyzed. Three conditions were used to analyze how distractor stimuli may affect reversal rate of the Necker Cube. The first condition consisted of a quiet environment with dim lighting. The second condition was composed of an atmosphere in which the radio was playing music chosen by the subject, a conversation between researchers in the background, and lighting was moderate. Finally, the third condition incorporated music chosen by each subject, conversation between researcher and subject, the smell of peanut butter cookies or french fries and a brightly lit room.
Procedure: Subjects were randomly placed in one of three various conditions, depending on condition used. The illusion was presented to each subject individually and subjects had a two-minute time period to continually reverse the illusion. Each time a reversal occurred they were instructed to push a particular key. If the reversal was coming towards them then the subject pushed f on the keyboard, and if the illusion was going away from them they were to push b. The illusion was identical in each condition; the only variation was in the environment.
Results
Figure two shows a graph of the mean results for each of the three conditions. Condition one has very wide time variability, while condition three has much lass variability. Although the results are not statistically significant, they do suggest that concentration may have an effect on the reversal rate.
Discussion
The wide variability in the high concentration group may be due to internal factors that influence concentration. The shorter intervals between flips in the low concentration group does not support the fatigue theory. It seems to suggest that there is another mechanism causing the flips. Although these results were not significant, this may be partly due to the small number of participants. There is also a lot of individual variation in viewing; other researhcers have found practice effects (Schellinger and Beer 1993).
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