Analysis of variance of the HHPO-free group and normal individuals shows that their VFAs differ as a function of test-time (p<.05). Using t test analyses reveals that these groups do not have significantly different VFAs at the immediate and 30-second test-times, but differ at the 60-second interval (p<.01). In other words, during the earlier stages of sensory input the HHPO-free patient's brain shows a similar level of augmenting as the normal brain, but as this stimulation continues, unlike the normal response, this patient switches to extreme neurological reducing. According to Petrie, this patient would be experiencing a "... turbulent ... unpredictably expanding and contracting sensory environment" (1978, p. 78). This kind of perceptual instability would not just be confined to figural displacement as measured in the present study, but also would include changes in depth, brightness, size and shape perception, and could as well involve instabilities in other sense modalities (Koehler & Wallach, 1944; McEwen, 1958).

Since these patients manifest perceptual instabilities within less than two minutes of rather intense sensory stimulation as the present study indicates, it would be reasonable to expect that they would also experience changing perceptions over much longer periods of time, especially in stimulating and stressful environments. Consequently, it should not be surprising that when they take the HOD, they will admit to many changing experiences described by the Test, and thus have relatively high scores. A quick reading of the HOD will reveal that most of the statements deal with changing visual experiences, changes in hearing, touch, taste, etc., and include words such as "sometimes, often, now and then, much more, at times, before, lately", which describe changing states.

By way of contrast, analysis of variance of the HHPO patients and normal group shows that they do not differ in the rate of change of the VFA as a function of test-time (similar cerebral augmenting - reducing range). That is, as sensory input is intensified, these patients maintain the same degree of perceptual stability as the normal group. When Dr. Osmond (personal communication) first saw the three VFA curves in Figure 1, his immediate response was that, in one sense, substances associated with HHPO may actually be beneficial in that they appear to combat perceptual instability. These data suggest that when an HHPO patient is bombarded with sensory input, his/her chemical state produces neurological reducing, and thus narrows the range of augmenting - reducing, thereby stabilizing the patient's perceptual world.

Dr. Osmond's observation becomes more significant when one considers that substances associated with HHPO may be CNS depressants. According to Dr. Irvine (personal communication), based upon the known CNS depressant effects of kryptopyrrole, HHPO may be classified as a CNS depressant. The effect sof CNS depressants on both figural aftereffect phenomena and cerebral evoked potentials have shown a tendency toward reducing (Barnes, 1976). Thus, if the substances associated with HHPO have a depressant effect on the CNS, then they would be expected to produce the differences in the VFRA found between HHPO and HHPO- free patients in the present study, namely, a tendency toward neurological reducing in HHPO patients, thereby narrowing the augmenting - reducing range, and thus stabilizing their perceptual experiences.