Perception of illusions and depth during a "transcendental state"

The experimenter employed an experimental group of 14 practitioners of Transcendental Meditation (TM) and a control group of 14 persons solicited from introductory lectures on TM to examine the effects of regular practice of a meditation technique on three tasks involving geometric illusions and one task involving secondary cues to depth. The meditators were asked to meditate and the non-meditators were asked to relax for twenty minutes. After this period they were presented with a counterbalanced sequence of the Muller-Lyer, Ponzo, and Poggendorff illusions and a depth cue task involving seven figures containing differing amounts of depth information. There were no significant differences between the groups on any one task, but, collapsing across tasks, 6 the experimental group showed significantly less error than the control group. (p< .05). On the illusion tasks there were significant differences (p< .00003) between the two directions of change of the variable part of each stimulus. On the Muller-Lyer illusion there was a significant difference (p< .01) between the first and second presentations of the task. The experimenter discussed the possible effect of dissimilar drug histories of the two groups on the results.