Hypnotic age regression and the Ponzo and Poggendorff illusions

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Abstract
Parrish, Lundy, and Leibowitz (1968, 1969) reported that the magnitudes of the Ponzo and Poggendorff illusions obtained from 10 hypnotically age-regressed Ss were consonant with illusion data obtained from young children. The present study sought to replicate this finding using additional controls. Insusceptible Ss simulating hypnosis were used to equate “demand characteristics” in the experimental and control groups. A group of medium susceptible Ss was included as a further means of assessing differences between high and low susceptible Ss, should these occur. Post-experimental inquiry procedures were used to evaluate the extent to which the results were affected by Ss' perceptions of the experimental procedure and by their preconceptions of how children should respond to illusions. 18 university students (6 high, 6 middle, 6 low), whose hypnotic rating had been ascertained using SHSS:C (Weitzenhoffer & Hilgard, 1962) and the Diagnostic Rating Procedure of Orne and O'Connell (1967) underwent the procedures used by Parrish, Lundy, and Leibowitz. The present study was unable to replicate the original findings in any of the comparison groups. It was not possible to account for the failure to replicate, though differences between the 2 studies in selection of hypnotic Ss and in the use of simulating controls were pointed to as potential factors.