Most of our basic drives, the ones that are with us from birth, are survival related. Those animals who didn't enjoy eating didn't survive long; those who didn't enjoy sex, didn't have many offspring. Many of us receive pleasure from solving intricate mental problems; taking pleasure in mental activity lead our ancestors to develop high intelligence. It's easy to see how taking pleasure in such activities would be selected for. But how does a desire to experience states of sensory distortion (often at great risk and unpleasantness, considering the side effects of many drugs, and the physical danger people expose themselves to in questing after some "natural" highs) arise from evolutionary processes? This hardly seems to be survival oriented behavior.
Some drugs (such as cocaine) directly stimulate "pleasure centers" that are naturally activated by our basic drives, or act in less direct ways to make the user feels more energetic and alert; it's not difficult to see how such experiences could be desirable. And others, such as the tranquilizers mentioned by Changeux and sedatives such as barbiturates, provide a way to escape from unpleasant stimulus. But the pleasure derived from sense-distorting hallucinogens such as LSD, psilocybin, and mescaline is harder to explain.
Even more difficult to understand is the pleasure taken in such non-drug sense-distorting "highs" as those sought by children. Infants rock themselves into bliss; children whirl or spin (a behavior also found in adult behavior such as dancing) or roll down hills (a time-honored recess pastime when I was in elementary school). Many children also experiment with hyperventilation followed by asphyxiation. Many adults seek out such "natural" highs in sensory deprivation tanks, "thrill" sports, and meditation classes.
Lest one think that such behavior is a human foible, we should remember that many animals will deliberately seek out intoxicating plants or alcohol-containing fermented fruits; the most familiar example to most of us would be the behavior of cats exposed to catnip. And it is possible that some animal behavior, such as tail- chasing, is an analog to the child running in circles.
The mechanism of "natural" highs, at the synapse level, is reasonably well understood; generally speaking, certain neurotransmitters or hormones are produced in more than normal quantities, causing an alteration in the normal flow of operation. Drugs can mimic the action of such chemicals, producing similar results, but the effect of even such powerful psychedelics such as LSD can be obtained without chemical help. Consider how one individual, given a harmless placebo and told it was LSD, described his experience:
A lot of strange shapes and brilliant color, after- images, as if I looked through pebble finished glass...colours were more brilliant than I have ever experienced. Voices were at times somewhat in the distance along with a feeling of not being in a real situation...time is distorted, goes rather slowly, an hour is only 10 or 15 minutes when I look at my watch.This is a perfect description of the LSD state. Even more interesting, when the subject was told what he had been given, and then a week later was given a normal dose of LSD, he reported no effects.
The effects of altered states of consciousness on mental functioning are quite interesting. One fascinating example is found in the habituation patterns of persons engaging in zazen, seated Zen meditation. In one study of EEG readings of persons in in zazen, two groups, a control and a group of meditating Zen masters, were exposed to a click every fifteen seconds. The EEGs indicated that in the control group, after three or four clicks, the sound was screened out; it had been habituated to. However, for the Zen masters, each click was responded to in the same way. The meditative state seems to increase sensory awareness, and decrease habituation (or increase dishabituation).
The LSD state also seems to have an enhancing effect on sensory awareness. Another LSD experiment examined measured two- flash discrimination ability (the ability to distinguish a single flash of light from two brief flashes with a very short interval between them) and response time of subjects who were given dexamphetamine and LSD. Perceptual discrimination was greatly enhanced in those subjects in the early stages [*] of LSD's effects, much more so than in subjects given dexamphetamine, but response time was adversely effected - perhaps because subjects were being distracted from the experimental stimulus by the enhancement of background stimuli.
An important clue to the nature of these states is their natural appearance in situations of stress or danger. We've all heard, or experienced, how in dangerous situations time seems to slow down, and perceptual details become clearer. (People's descriptions of car crashes probably form the classic example.) Clearly, this is of use in survival; the time distortion gives us more "time", by our subjective measurement, to solve the problem, and the enhancement in sensory awareness give us the necessary information. We have no information on whether other animals experience similar subjective changes in awareness, but it seems reasonable that this "mental overdrive" may have evolved as a way of concentrating processing power and amplifying sensory input in emergencies. Perhaps by entering these states when there is little or no danger, we develop our brains to better utilize this mode in emergencies. If this is so, those of our ancestors who found such mental exercise pleasurable would have been better equipped to deal with survival-threatening situations, and would have had an evolutionary advantage.
And it may be that the hallucinations we associate with many of these states of consciousness may result from overamplification, or saturation of the sensory inputs, in the same way that turning up a stereo amplifier's volume control too loud introduces distortion. Many people have used hallucinogens and consciousness-altering activities in an attempt to gain insight into parts of their own minds not normally accessible. If one thinks of the overamplification as producing mental "white noise," the responses of other parts of the brain would be dependent on their structure. We filter this sensory noise through our preconceptions and knowledge as encoded in our neurons. Hallucinations may act like supercharged Rorschach inkblots, allowing those who experience them to psychoanalyze themselves - a valuable ability in members of a complex social structure.