THINKING, IMAGERY AND MEMORY 1 673 



subjects with brain lesions, from normal subjects 

 under influence of certain drugs and from lower 

 animals. Correlation technique, as applied to EEG 

 data, permits systematic variation of the time di- 

 mension in an ongoing train of space-time events. 



The coefficient of correlation is a convenient mathe- 

 matical expression of coincidence in time and space. 

 Multiple correlation techniques permit similar han- 

 dling of multiple variable problems (see fig. 2). 



If it were possible to place electrodes, strain gauges, 

 flow meters, thermistors and chemoindicators in such 

 way throughout the brain as to isolate and identify 

 critical variables in the neural pool, the resulting 

 correlation matrix generated by comparing each 

 variable against every other variable would remain 

 beyond comprehension, without some means of 

 integration. 



It is possible that a method known as factor analysis 

 will supply such integration. A model illustrating the 

 significance of this method appears in figure 3. Factor 

 analysis has already been applied successfully as a 

 secondary check on experimentally isolated functions 

 in neurosurgical cases (15). It would be interesting to 

 know, for example, whether factor analysis of ana- 

 tomicophysiologic data would confirm the existence 

 and boundaries of such a priori neural systems as the 

 reticular, limbic, rhinencephalic and centrencephalic. 



BIOLOGICAL INTELLIGENCE 



From the study of behavioral effects of selective 

 ablation of various parts of the brain in man, and 

 appropriate controls, Halstead (15) has developed a 

 concept of biological intelligence. This form of intel- 

 ligence is relatively independent of that presumably 

 reflected in the standardized psychometric test of 

 intelligence which yields an intelligence quotient 

 (I.Q.). Whereas the I.Q. appears to predict reasonably 

 well the ability of the individual to perform secondary 

 school work and less well college work, it does not 

 predict reliably the deficits in general adaptive 

 capacity which tend to be characteristic of forebrain 

 (frontal lobe) lesions in man. Biological intelligence 

 matures somewhere around 14 to 15 years of age and 

 may, in some individuals, be maintained at a high 

 level even through the sixth and seventh decades of 

 life. It appears to its author to have maximal represen- 

 tation in the cortex of the frontal lobes since neuro- 

 surgical Lesions in this area produce the greatest 

 deficits. It is, however, directly represented to .1 lesser 

 degree throughout the cerebral cortex and quite pos- 

 sibK in some subcortical structures. Halstead regards 

 the frontal lobes .is representing the last stage in the 

 evolution of cortical mechanisms and holds that 

 analysis of their functions provides an important clue 

 to cortical mechanisms in general. 



Other investigators, including Reitan (50 . using 



fig. 3. Spherical model projection of factor analysis solution 

 of 15-variable problem reduced to 3 factors. Each spindle or 

 vector represents an individual test. For each cluster of tests a 

 'factor' is postulated. [From Thurstone (56).] 



fig. 4. Apparatus developed at the University of Chicago 

 for measuring higher brain functions in man. The apparatus 

 provides stimulus material of various levels of complexity for 

 the eve. the ear and the sense of touch All responses arc- ob- 

 jective and nonverbal in character. The data are programed 

 on IBM cards. See text, and Halstead (15) and Reitan (50) 

 for discussion of the various indicators employed in the ap- 

 paratus. 



