The Brain and Behavior 59
Franz, 1907, p. 12). As indicated above, these portions of the
cortex were called association areas because they were be-
lieved to connect sensory with motor areas. For various rea-
sons the frontal lobes were singled out as the most probable
locus for intellectual processes. Data from comparative anat-
omy identified this region of the brain as tire last to develop
in mammals and as most highly developed in man (Ferrier,
1886, p. 466; Ariens Kappers, Huber & Clark, 1936, Ch. X).
In addition a number of clinical studies of brain tumors or
traumatic lesions in human frontal lobes gathered during the
19th century reported intellectual deficits, although as Franz
(1907, Ch. II) has indicated, there were an equal number of
cases in which no deficit was reported. In spite of this
equivocality Ferrier (1886) felt justified in stating, “We have
. . . many grounds for believing that the frontal lobes . . .
form the substrata of those psychical processes which lie at
the foundation of the higher intellectual operations” (p. 467).
However adequate or inadequate the initial grounds might
have been, a large amount of research has been undertaken
to explore the significance of the frontal lobes for intellectual
processes.
The problems involved in demonstrating the relation of the
frontal lobes to intellectual processes were more difficult than
those encountered in exploring the significance of the sensory
and motor areas of the cortex. In the latter case, electrical
stimulation of the tissue had a definite effect, although, as
recent research has demonstrated, the relevance of these ef-
fects for the function of the central nervous system is not yet
clear. However, with the exception of the somatic motor area,
stimulation of the frontal lobes had no effect and the neuro-
physiologist had to vary systematically both his cortical pro-
cedures and his behavioral measures. As a consequence re-
search on this problem has been controversial from the start.