There is additional evidence that brain size and cell count do not tell the whole story as relates to intelligence. Early man, dating back to approximately 100,000 B.C., had a brain size comparable to our own, but it wasn't until 15,000 B.C. that he began painting on cave walls, 5,000 B.C. that cities began forming, and 4,000 B.C. that he devised a form of writing. Man's larger brain size appeared to endow him with a potential that we are only now beginning to more fully realize.²⁸

It should also be pointed out that brains of idiots are sometimes physically larger than those of great intellects and some geniuses have comparatively small brains.²⁹...This again stresses the importance of how the evolution of intelligence has as much to do with the rearrangement of synaptic connections as with the physical increase in brain size.

Anthropologist Sherwood L. Washburn has stated that the evidence indicates it was after humans began making tools that the real explosion in brain size occurred. Their tools, used in a great variety of ways, helped to stimulate a more rapid growth of the forebrain.³⁰

A large brain provides only the potential for high intelligence. Any brain not properly stimulated will not develop.

There are many environmental factors which are continuously competing and that alter one's level of manifested effective intelligence. This level is unquestionably in a constant state of flux. We are ordinarily not aware of any change occurring since most of the time the difference is too small or happens too slowly to perceive. It would also seem likely that what we are aware of at any one moment in time is our level of consciousness or awareness and not our level of intelligence per se. Unless an individual is in an altered state of consciousness, it would seem that the experience of ordinary consciousness is quite stable over time no matter what one's fluctuating level of intelligence is.

There is much evidence that human physical and mental processes vary greatly based on daily and other temporal cycles. Chromopsychology has emerged as a new field to study cyclic effects on body and mind. There are biological rhythms ranging from 90 minutes to annual cycles that affect physical, emotional, and cognitive aspects of human behavior, and undoubtedly affect other animal behavior as well. Many activities have a "best" or most likely time of day. There is a substantial fluctuation of hormones, minerals and other chemicals in the blood throughout a 24-hour period that is cyclic. Circadian cycles also appear to influence mood, blood pressure, pulse rate, body temperature, cell division, immune response, learning ability and other cognitive processes. Shielding individuals from electromagnetic fields or changing their geographical location will alter their circadian rhythm.³¹

It has been clearly demonstrated in research studies how various drugs can enhance or diminish memory. High altitude can also significantly influence learning and memory. Studies performed on climbers who were high enough to experience some oxygen deprivation showed they experienced hyperventilation, hormonal changes, and impairment of verbal learning and short-term memory. These deficits did return to normal in time.³²

It would appear that stress can reduce effective intelligence, according to research done by Bernard Brown of the Department of Health and Human Services in Washington, D.C. A group of white middle-class children had an average drop in IQ score from 105 to 91 and had diminished capacity for complex tasks and complex thinking after being subjected to stress.³³

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