level than this, but with the primates (especially chun- 

 panzees and Man), there is learning, memory and thought 

 taking place within the prefrontal lobes of the brain at a 

 conscious level, as well as subconscious mental activity. 

 Studies of chimpanzee behavior, undertaken notably by 

 Kohler, have shown the mental capabilities of these ani- 

 mals to be considerable: chimpanzees can solve problems 

 involving manipulation of their environment to attain par- 

 ticular objectives, using sticks, ropes and boxes in ways 

 like those used by Man, and requiring trial and memory 

 for their successful solution. But without a language to 

 specify objects, the chimpanzees are unable to go further 

 than what, to Man, are simple operations. There seems 

 little doubt that the development of spoken language has 

 made possible Man's great mental development, assisted by 

 Jiis inherent manual dexterity and accurate vision. Later 

 the written language, and still later mathematical sym- 

 bols, have even further advanced our mental capabilities. 

 Another most important series of experiments on men- 

 tal activity began with the first observation, by Berger in 

 1929, of actual waves of electrical potential changes taking 

 place in the brain during thought, which waves were 

 sufficiently strong to be detected by electrodes placed on 

 the head surface. These so-called "brain waves" were 

 found to be of a very complex nature, but definite rhythms 

 at frequencies of from about 8 to 13 cycles per second 

 were present. Further experiments have been performed 

 on the exposed brain of normal and abnormal subjects, and 

 have revealed the sites of electrical activity corresponding 

 to stimulation of the various senses. In its nervous circuitry 

 the brain resembles the modem electronic computers with 

 their switching transistors and ferrite "memory" cores — 

 indeed these computers perform logical processes in a 



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