HUMAN IN MINIATURE
THE BRAIN OF THE CHIMPANZEE
The chimpanzee has a well-established reputation for many sterling
qualities. He is a comedian of no mean talent, and often as a buoyant
fun maker earns a large salary. He is also famous as an acrobat.
Depending upon his species, the chimpanzee varies in height from four
feet to four feet five inches. As a class these apes are spread out
over more territory than any of the other great anthropoids. They live
in West and Central Equatorial Africa ranging from Gambia in the north
as far south as Angola. In colour they are black with thick hair over
the entire body, except the brow and face. In some species the scalp
is bare, as in the bald-headed chimpanzee. All varieties are powerful
but lightly built animals. They possess great strength and agility. In
spite of his relatively short stature, the chimpanzee is a dangerous
enemy even for the strongest man. His head is flattened in the region
of the forehead, which has a thick bony ridge above the eyes. The ridge
of the nose is flat. The mouth is large and the lips thick. The ears
are especially large and project upward almost as high as the vertex of
the head. The lower jaw protrudes considerably. The teeth in general
are large and formidable, the canines in particular being prominent.
The skin over the face is usually dark, but in some species it is
lighter than surrounding areas. This is particularly true in the region
of the mouth and nose. The body is short and the abdomen pendulous.
The legs are shorter than the arms. The foot is short with a great toe
that is thick and opposable. The other toes are united by a web near
the base. The arms are long, with finger tips reaching a considerable
distance below the knees when the animal stands erect. The hands are
broad, the thumb is short, and the fingers webbed near their bases, as
in the case of the toes. As is true of the other great anthropoids, the
chimpanzee has no tail. The female bears one young at a time, which she
carries when passing through the forest and along the ground in the
manner characteristic of other apes.
_Intelligence of the Chimpanzee_
Concerning the habits of the chimpanzee in its native state little
is known. Fortunately, many of these animals have been captured when
young. Some of them have become noted circus performers, or famous
moving-picture actors. A number of them have been studied from the
standpoint of their behaviour and psychology. One of the best records
of the chimpanzee comes to us as an echo of the Great War. It furnishes
another instance of German thoroughness and scientific enterprise.
Some years ago the Prussian Academy of Science established at Teneriffe
in the Canary Islands a special station equipped for the study of
the great manlike apes. It was here that Professor Köhler found
himself during the Great War and here he remained interned with nine
chimpanzees for two years. During this time he lived with these animals
largely shut off from the rest of the world by the naval blockade.
The report of his experience and studies is given in a delightful
narrative published both in English and German called _The Mentality
of Apes_. The following descriptions of the chimpanzee are taken from
Professor Köhler’s book. In this work his chief purpose was to test the
intelligence of the larger manlike apes. To this end it was necessary
to devise certain methods which he called “roundabout tests” because
they complicated ordinary situations in such a way as to require
intelligence on the part of the animal for their solution.
Early in the study one of the most quick-witted chimpanzees in the
collection was given the following problem: From the roof of the
animals’ playground a basket of bananas was suspended by means of a
string passed through an iron ring. The end of this string was tied
in a noose and placed over the limb of an old tree at a height of
nine feet from the ground. When all was ready, the chimpanzee called
“Sultan” was sent out into the playground. He, of course, was familiar
with this basket and associated it with feeding time. On entering the
enclosure Sultan saw the basket at once and then began to manifest
signs of agitation because, contrary to custom, he was all alone in the
open. He began at once to show his feelings in true chimpanzee style.
Jumping about he expressed his extreme disapproval at being alone by
making a thundering noise with his feet against the wall of the ape
house. It seemed as if he were calling upon the other chimpanzees to
come out and join him. He even tried to get in communication with the
other animals by climbing up and looking in at their windows. But
all of this was to no avail. Presently he appeared to take a renewed
interest in the bananas. He looked up at the basket, and having sized
up the situation made for the tree, climbed quickly to the noose,
pulled the string until the basket bumped against the roof, released
the string, pulled it a second time even more vigorously, until a
banana fell to the ground. Sultan then left the tree, but soon ascended
once more, now to pull violently upon the string until it broke and the
entire basket fell. Immediately he scampered down, took the basket, and
went off in a corner to eat the fruit. Thus Sultan, in a comparatively
brief time, solved this roundabout problem by obtaining the objective
in spite of the obstacles put in his way.
_The Chimpanzee’s Use of Implements_
Many experiments were made to see how much the chimpanzees make use
of implements, but in the main these experiments were not necessary.
The chimpanzee, as if by nature, handles many objects in his immediate
surroundings in a variety of ways. His powerful hands serve in a
most natural manner as a useful link between him and the world of
things outside. His feet, although far more than a second pair of
hands, may be used in emergencies when the human feet would be quite
useless. The jaws and teeth are also serviceable, and are employed as
among many African tribes and other primitive people. The handling
of everyday objects by the chimpanzee comes almost entirely in the
nature of play. Sometimes under the pressure of need it appears that
new knowledge acquired from using objects at play will be put to still
better use in gaining some desired objective. In the main, however,
what the chimpanzee may use in this way is without the slightest idea
of immediate gain and serves only to increase the joy of living.
Thus jumping with the aid of a stick or pole, invented by one of the
brightest chimpanzees, was imitated by all the others as a means of
entertainment. Later it was put to more practical use for obtaining
food which was suspended above them and out of reach. In order to get
this food it was necessary to resort to some means of lifting their
body toward the desired goal. In the end the jumping with a stick in
play was converted to a sort of pole vaulting by means of which the
chimpanzees all acquired a thoroughly businesslike method for getting
such food as was out of reach over their heads. These chimps also used
straws and twigs as we use spoons. At first this was more or less in
play during mealtime, especially after their first thirst had been
quenched. Then they liked to amuse themselves by dipping the water up
with a straw and sucking the straw. Once some red wine was poured into
the drinking water which they shared in common. At the first taste of
this new mixture they all paused for a moment and looked at each other;
then one of the chimpanzees began to spoon up this wonderful drink
with a straw, and all the others immediately followed his example. In
learning to use twigs and straws for spoons there was no possibility of
imitation. None of the chimpanzees had a chance of seeing a human being
use a knife or spoon while eating. The twig or stick was also employed
quite deftly in other ways, adding to its usefulness as a table utensil
some of the properties of a weapon for the chase. In the summer time a
species of ant infests the part of the Canary Islands where these great
apes were housed. These ants passed in a wide stream, moving along
over the beams, around a wire netting which encircled the playground.
The chimpanzee has a great liking for acid fruit, which he prefers to
all others. It is no doubt for this reason that he relishes the formic
acid in the ants. Usually upon seeing the ants the chimpanzee simply
rolled his tongue along a beam over which they were crawling and thus
gathered them in to himself. If the wire netting came between him and
this coveted delicacy, such a method of capture would not suffice. In
consequence, all of the chimpanzees soon learned to use sticks and
straws, which they thrust through the wire netting and held in this
position until covered by ants. The straws were then withdrawn, and
the insects promptly licked off and devoured. This method of capture
proved most satisfactory and entertaining. Their attention was entirely
absorbed in the process of overcoming the obstacle between them and
the delicate morsels which they craved.
_Strong Human Resemblances_
If a mouse, a lizard, or some small crawling animal entered the
playground, the chimpanzees at once became greatly excited. They
manifested all of the hunting interest apparent in the human species
under like circumstances. There was also evidence of fear and timidity
on these occasions, not, however, confined to the female alone. Even
the bolder chimpanzees that evinced the greatest hunting interest did
not give chase with any creditable show of courage. They manifested
caution and hesitation throughout the entire performance. Nearly
every movement on the part of the poor quarry was followed by nervous
gestures of the chimps. The largest ones hesitated to make a capture
by a sudden snatch with the naked hand. It was amusing and almost
laughable to see these powerful apes stretch out their hands with the
evident intention of catching the prey, with fingers all pointed in
anticipation, then suddenly, on the slightest movement of the mouse
or lizard, quickly withdraw the hand again. A firm grasp upon one of
these little wriggling animals appeared almost as impossible for the
chimpanzees as for many people. Despite the great excitement which the
presence of invaders occasioned, the little animals would often escape
because the chimpanzees lacked that last degree of daring necessary to
make a successful capture. Presently they learned to use sticks upon
the small intruders of their domain. With these weapons, if the victim
did not escape, they would at length dispatch it. This they did in no
spirit of cruelty but rather in sheer excitement of the chase.
Professor Köhler took great pains to observe the rapidity with which
the chimpanzees adjusted themselves when confronted by new conditions
for the first time in their lives. One of the most striking tests
of this kind was their introduction to the electric current. It was
decided to observe how the chimpanzees would act when they made the
acquaintance of this entirely new circumstance. For this purpose one
wire from an electric induction coil was attached to a metal basket
filled with bananas and suspended from the roof. The other wire from
the battery was made fast to a metal netting upon the ground beneath
the basket. In a short time all of the chimpanzees became intensely
interested in the fruit above their heads. They were particularly
eager to reach the bananas. To do so it was necessary for them to
stand upon the wire netting on the ground. At first one chimpanzee
approached cautiously. Having taken up his position with both feet
upon the wire netting, he reached slowly up to the metal basket.
This of course immediately made a connection which delivered an
electric current through his hand. The reaction of the chimpanzee was
astonishingly human. Immediately upon touching the basket he felt the
shock of the current and with a cry of dismay bounded off in great
surprise. His curiosity, however, was not yet satisfied. He still
had a hungry longing for the bananas. Everything about the situation
looked thoroughly familiar and innocent to him. He could see no reason
why the basket on this occasion should treat him so rudely or why he
experienced such an unpleasant sensation in trying to get his food as
he had done a hundred times before. Appetite and curiosity finally got
the upper hand, and stealing up cautiously he made a second attempt.
This time he was less hasty in grasping the basket and spent several
moments in hesitating attempts to touch it, drawing his hand back now
and again. At length, with a sudden grasp, he reached for the goal,
only to receive another shock. In apparent indignation he hopped away
in much the same manner as might any human being who had inadvertently
touched a hot stove. Nothing would do, however, but that all of the
chimpanzees in turn should follow the example of their leader and try
to get the bananas away from this strange thing that seemed to be
outwitting them. One after another they made their futile attempts
until it became a pathetic sight to see them sitting around in a
mournful ring, sometimes looking at their hands, sometimes shaking
them resentfully, and always gazing wistfully at the inaccessible
delicacies. Most of the chimpanzees during this test reacted in a
manner which might easily be called human. It was rather impressive to
observe that all of their reactions under these conditions were actual
counterparts of human behaviour.
_Chimpanzee Sports and Nest Making_
In handling other objects the chimpanzees showed a strong tendency to
develop new habits. After a time they did not confine themselves alone
to thrusting and hitting with sticks. They soon began to throw them
around. In moments when they were greatly pleased (and chimpanzees
have a joyful, buoyant nature) they showed their delight in a new way,
especially when very good food was being provided. On such occasions
one of them would seize another and shake him violently out of sheer
pleasure and approval. Under such provocation a large chimpanzee
developed the habit of taking a stick and flinging it forcefully
at some comrade in his vicinity. This frequently happened in play
also. One female, a remarkable athlete called “Chica,” developed the
amusing pastime of stealing up behind her companions as they sat
quietly at rest, and from fairly close quarters hurling a stick at
them. Immediately she would scurry off, apparently much delighted by
the discomfort that she had caused. From throwing sticks it was but a
short step to throwing handfuls of sand at one another, and finally
stones of varied size and weight. At first their aim was poor, but soon
throwing stones became a ruling passion among them, and some of them
became dangerously expert, especially the wily Chica. She practised so
continuously that she soon acquired great skill and an excellent aim.
From this pastime she appeared to derive much satisfaction, whether
hurling stones at her fellow apes or at her human associates. Both
ape and man acquired such a genuine respect for her ability in this
regard that whenever they found her in this mood they quickly retired
to safety and permitted the expert marksman to find her amusement on
less sensitive targets. All of these hurling activities, which were in
the nature of play, might for a few moments determine an exciting stone
battle. But the sharpshooting Chica was so obviously superior that the
fray was certain to be short lived.
Almost all of the chimpanzees made nests for themselves, even from the
earliest infancy onward. In these operations, as might be expected,
the full-grown chimpanzee made the best beds. It may not be altogether
clear why the adult female was the best chambermaid of all. Her
efforts in bed making did in fact show a precision in tidiness that
was unequalled by any of the others. Usually in the evening, as the
strenuous play of the day subsided, all of the apes began to gather
heaps of straw. In the centre of each heap a chimpanzee would sit
quietly and begin to twist the ends of the straw together. This work
continued all around the edge until a natural nest, not unlike that of
the stork, was formed. The younger animals in their nest making were
less exact. They seldom made so neat a turning down of the outer edges,
but on some occasions, when they apparently took more pains with their
handiwork, their movements during the preparation of the nest were
exactly like those of the older females. Nests were often made during
the day in pure fun, and many different materials, such as string,
grass, branches, rags, ropes, and even wire, were collected for this
purpose. It was quite evident that in their nest-making activities the
younger chimpanzees imitated the actions of the older ones.
_Clowning and Masquerade_
Objects of many kinds interested these apes. They seemed particularly
fond of carrying quite a variety of rubbish about on the body in one
way or another. Nearly every day some of the animals began walking
around the playground with a piece of rope, a bit of rag, a blade of
grass, or a twig upon the shoulders. Some of them if given a bit of
metal chain would put it proudly around their necks like a necklace.
Bushes and brambles were often carried in considerable quantities
spread out over the entire back. In these actions they affected a
manner that revealed tendencies familiar to human masquerading in
grotesque or fantastic costumes. One of the chimpanzees contracted the
habit of carrying around empty preserve cans by grasping the lid of the
can between his teeth. All of this occupation was done as diversion
or entertainment, from which the chimpanzees derived much visible
pleasure. The clowning actions of these apes clearly held the attention
of those not actively participating in the performances, and many of
them, like little children, attempted to imitate the antics of the
leader. When dressed up in these various ways the chimpanzees often
displayed an almost impish self-important audacity, strutting about
among their companions or advancing upon them in a menacing way. One
of the older females, attired for play, would trot around in a circle
with several of the smaller animals following closely at her heels.
Sometimes the entire company playing in this fashion would march around
in a circle, one behind the other. The largest animal would stamp its
foot at each step, as though beating time for the parade. The other
animals followed suit by an accentuation of the marching movements.
_Manufacture and Building_
Not only did the chimpanzees acquire many ways for employing objects
which they encountered, but some of them actually went one step
farther. They manifested a degree of ingenuity in constructing special
implements for themselves. The results of this constructive industry,
it must be admitted, were relatively simple. On the other hand, there
can be no doubt that the chimpanzee does manufacture instruments, in a
modest way, which help him to gain his ends. One of the most talented
apes learned to fit a small piece of bamboo into the cavity at the
end of a larger piece. In this way he built a long bamboo pole, which
was especially useful for procuring food hung above his head and out
of reach. All of the chimpanzees ultimately developed some degree of
constructive or engineering ability. They actually became builders on
a small scale. This ability grew out of their learning to use boxes
in order to reach objects over their heads. Using one box led to the
advantage of piling one box on top of another and thus constructing
a tower. They were not all equally expert as builders. As might be
expected, the more quick-witted and alert members of the group learned
how to build first, and this they did entirely of their own initiative.
After they had built a tower of this kind, the long bamboo stick came
in handy as a means to bring the suspended banana to the ground.
Here two modes of solving a problem were combined--that of building,
and that of using the long pole. Building operations soon became a
favourite pastime; yet in spite of the fact that they were given every
opportunity they never developed an efficient labour organization.
However helpful united efforts may have been toward their ultimate
aim, the chimpanzees failed to realize the advantages of a mutual aid
society. There was doubtless a reason for their lack of intelligence
in developing higher efficiency in this respect. Almost invariably
their building operations were dictated by a desire to obtain food
that was out of their reach. Among the chimpanzees this goal was in no
sense a mutual interest. It was a matter of the utmost selfish concern
to each chimpanzee. So whatever advantage there might have been in a
division of labour, there was never a thought of dividing the spoils.
When the chimpanzees gravely assembled in the presence of a basket of
food hung up over their heads, they gazed about for proper materials
to use as tools in reaching the desired goal. One would bring a pole;
another would drag up a box. These were put in position preparatory to
constructing a tower. The building would then begin in earnest. When
the first stages of construction were complete several of the animals
at the same time would show great impatience to clamber up. Each one
of them acted as if either he or she were the sole proprietor of the
structure. Often, too, the box already in position would be snatched
away by some competitive group in the building industry and dragged off
to be used in the construction of a rival tower. This would usually
result in a wrangle among the architects. In fact, the entire company
of builders might come to blows over this infringement of property
rights. After the subsidence of these Babel-like controversies the
building would be resumed and the structure would continue to grow
in height until it became an object of ever-increasing excitement to
the assembled workers, each manifesting a keen desire to mount it. In
consequence of this highly individualistic competition and due to their
restless efforts, the tower would sometimes tumble over and the result
of their labours be destroyed. Then it was necessary to begin all
over again. Usually in this renewed effort only the more diligent and
patient of the chimpanzees adhered to the original purpose. The others
became interested in more trivial occupations. Eventually the tower
was finished, and the more diligent as well as the more patient of the
toilers quietly mounted to the summit of the structure and, either
with or without the aid of the pole, obtained the coveted bananas.
Sometimes, however, just when the diligent one was ready to reap the
just reward of his efforts, some member of the group endowed with
unusual athletic prowess rushed up stealthily and with great speed to
the top of the tower and seized the prize before the rightful winner
had time to protest or retaliate. In all of this building enterprise
there is something so fundamentally human, so reminiscent of modern
methods, that it seems inaccurate to class these reactions too rigidly
in the category of ape behaviour.
_Emotions of the Chimpanzee_
The chimpanzee, according to Professor Köhler, has a range of
expression of emotion even greater than that of the average human
being. The chimp shows his feelings by his entire body, not merely
by his facial expressions. It is his custom to jump up and down both
in joyful anticipation and in anger or annoyance. In extreme despair
or disgust, which the animal shows on slight provocation, he has the
habit of flinging himself upon his back, rolling wildly to and fro,
swinging and waving his arms about his head in a frantic manner not,
on the whole, very different from the way in which some non-European
races manifest their disappointment and dejection. The chimpanzee is
not known to weep, nor does he laugh in quite the human sense of the
term. There is something approaching human laughter in his rhythmical
gasping and grunting when he is tickled. While quietly watching objects
that seem particularly pleasing (and his greatest delight comes from
observing little children) the face of the chimpanzee, especially
around the mouth, has an expression not unlike a human smile. When
perplexed or in doubt, he has a way of scratching the surface of his
body, especially the arms, breast, or upper portions of the thigh.
It has not been stated that during these moments of perplexity he
scratches the head, as is the common human custom. He conveys his
meaning not only of emotional distaste but also of definite desires.
The expression of his wishes is in large part shown by direct imitation
of the actions desired. Thus, when one chimp wishes to be accompanied
by another, he gives the latter a nudge and pulls him by the hand. If
one chimpanzee wishes to receive bananas from another, he imitates the
movement of snatching or grasping accompanied by pleading glances. The
summoning of another chimpanzee from a considerable distance is often
accompanied by a beckoning that is very human in character. Their many
actions in all instances are characteristic enough to be understood by
their comrades.
_Surgical Interests_
The chimpanzee is especially prone to pay close attention to the wounds
or injuries received by his fellows. The motive of this attention may
scarcely be called mutual aid. The removal of splinters from each
other’s hands and feet is a favourite clinical operation. In this
pursuit the chimpanzee employs methods usually in vogue among the human
laity. Two finger nails are pressed on either side of the splinter,
which is thus elevated until it may be caught and removed by the teeth.
Professor Köhler himself, once having suffered from such an accident,
ventured to allow one of the chimpanzees to remove the splinter from
his hand. On perceiving the condition, the chimpanzee’s face at once
assumed an expression of eager intensity, and his attention became
concentrated in preparation for his surgical efforts. He seized the
hand, examined the wound, forced out the splinter with two somewhat
powerful squeezes of his finger nails, and then closely examined the
hand to be satisfied that his work was well done.
_Morals Among Chimpanzees_
There is much of interest in the experiences of another distinguished
observer, Dr. Charles F. Sonntag, formerly Prosector of the Zoölogical
Society of London, who has called attention to the fact that the
chimpanzee is said to be filthy in its habits. He observed that many
of these animals in captivity do not manifest such traits, nor do they
show any tendency toward immoral behaviour as has been claimed. It
seems unfortunate even to imply that such a delinquency as immorality
exists among chimpanzees or, for that matter, any of the lower mammals.
But since the point has been raised, it may be well to recall that
morals are of human making. They are designed to modify, to restrain,
or to prevent the development of certain animal tendencies which are a
human heritage from the great animal kingdom. If the chimpanzee in any
of its actions tends to depart from the code of morality established by
man in one part of the world or another, this can be no reproach to
the ape, since man himself has not yet been completely successful in
building up a system of restrictive laws to protect himself from the
devastations of his own animal inheritance.
Professor Köhler, from his long studies of the chimpanzees, concluded
that these apes manifest intelligent behaviour of a general kind
familiar in human beings. Not all of their intelligent acts are similar
to human acts, but by means of well-chosen tests the character of
intelligent conduct can always be traced in the chimpanzee. These apes
differ among themselves just as much as people do, in their mentality
and intelligence. Some of them may be mentally deficient, just as
there are mentally deficient human beings. One remark of Professor
Köhler’s is a keen social criticism with a wide application to life
in general. He maintains that the tests designed for the chimpanzee
serve two purposes: First, they determine the intelligence of the
apes; and, second, they test the intelligence of the examiner. This is
eminently true in all intellectual contacts between human beings. It is
a fact that the chimpanzees stand out among all other animals in their
form, in their actions, and in their understanding. In these respects
they come much closer to the human standard than any other ape, with
the possible exception of the gorilla. All of these observations
agree well with the theory of evolution, and in particular with the
close relations existing between the growth of intelligence and the
development of the brain.
Many other chimpanzees have been studied from time to time. The
conclusions drawn from them have been closely similar to those already
cited. Romanes some years ago studied the trained chimpanzee, Sally,
which was famous for her high degree of intelligence. Under training
this animal acquired the ability to count. She could draw a number of
straws to six or seven, and upon request would indicate with straws
the exact number she had been instructed to show. This achievement,
in combination with many other extraordinary performances, reveals
certain striking likenesses to man, particularly as to the degree of
the chimpanzee’s power to learn.
_The Chimpanzee’s Social Traits_
Others besides Professor Köhler are willing to give the chimpanzee
credit for unusual good-fellowship. All admit that he is a most
friendly creature. Often an affectionate attachment exists between him
and his owner or keeper. He is never loath to indulge in his clowning
performances to please and entertain his human friends. His actions
on these occasions have doubtless been the models for the ludicrous
mimicry of olden times now generally referred to as “aping.” In many
of the army encampments in Africa, monkeys and apes have been the
much-prized pets of the officers. It was not uncommon to find among
these pets the highly sociable chimpanzee. Frequently the officers
manifested much zeal and interest in training their charges and felt
a real pride in exhibiting them. Sometimes on gala occasions these
simian pets occupied places at the table beside their owners. They
partook in most approved style both of food and of drink. Not a
few of them have shown a distinctly human characteristic in their
strong liking for intoxicating liquors. The chimpanzee has always had
a decided penchant in this direction. At mess dinners and on other
occasions he not only manifested a keen liking for good wines but took
his share with the rest. Often he, like his human companions, rose to
hilarious heights. Often, too, it was necessary to lead him off to
bed in such a deplorable condition that he would appear next morning
with a shaky hand on his brow and that sad expression which plainly
told the consequences of festive revelry. One of these chimpanzees had
a particular fondness for afternoon tea and would join the officers’
group at this time as a matter of course. His manners were altogether
agreeable. He acquired all of the airs essential to such occasions even
to certain banal chatterings.
_In Prophecy of the Human Brain_
If doubts should remain concerning the superior and almost manlike
capacities of the chimpanzee, these may be soon put at rest by
inspection of his brain. In this organ there are indications of the
means by which the chimpanzee has acquired his new and extensive
powers of learning, his greater understanding, his higher capacity for
adjustments to life, and his many reactions which are so nearly human.
Every sense department in the superbrain has shown pronounced
improvements. A survey of the chimpanzee’s brain shows it to be a
mechanism better organized for the purposes of efficient output than
that of other apes and monkeys. It is a larger brain. It also has a
greater richness in grooves and convolutions showing that its capacity
for developing brain power has been much increased. The groove of
Sylvius has been tipped backward in consequence of expansions in the
department of hearing and the department of body and contact senses.
In the department of hearing (the temporal lobe) the convolutions are
more complex than in any other lower apes or monkeys. In fact, the
entire pattern of coil arrangement in this part of the superbrain
is similar to that seen in man. It has, perhaps, a simpler design,
but the essential features of the pattern may all be identified. In
the department of sight the same principle of expansion has been at
work. The convolutions in the occipital lobe have increased both in
number and complexity of arrangement. There are more grooves and more
convolutions in this region than we have yet encountered. Such also is
the case in the department for body and contact senses (the parietal
lobe), in which the grooves and convolutions manifest an arrangement
identical to that of man. The lesser brain, lying as it does tucked
away beneath the occipital pole of the superbrain, also shows marked
increase in size, so that the subsidiary department essential to
postures of the limbs and body, and also to balance, has kept pace
with the superbrain. Appraised on the value of its great working
departments, a brain like this reveals the manner in which progressive
development has advanced.
The organization for transacting the functions of hearing has been
greatly improved, if we judge by the enlargement of the temporal lobe.
Furthermore, it appears that certain sub-departments for handling
these transactions have been established. They doubtless have to do
with a better filing system for auditory impressions and especially
for correlating the impressions of things heard with similar records
of things seen. This method of cross reference produces a better
understanding of all objects encountered in the surroundings. A
practical illustration may assist in visualizing the manner in which
such associations operate. If in their home life the chimpanzees
are suddenly startled by the report of a gun, which they have never
heard before, the entire family may be greatly perturbed by the
harsh and unfamiliar sound. The sound alone might be startling and
disagreeable, but the sound cross referenced by the sight of the
hunter and gun comes to mean peril. Instances of this kind might be
multiplied to show how essential to success in life this system of
cross reference is. In fact, it is the amplification of this system
that underlies our progress as individuals or as a race. The structural
signs of this progress are to be found in the region of the brain
that we have been discussing. We may recognize them in the increased
number of convolutions which provide for better development of brain
power. Equally pronounced are the advances that have taken place in
the organization of body and contact senses. This department lies
immediately above the Sylvian groove in the parietal lobe. It receives
all communications transmitted from the outside world by the sense
of touch and by the various movements of the body. The convolutions
in this region indicate a highly organized department which we might
expect in view of the remarkable performances of the chimpanzee.
Walking a tight rope, eating his food with a certain degree of good
manners, drilling to music, or driving an automobile, the chimpanzee
clearly demonstrates how expert he has become in the use of his hands
and feet. His cleverness depends upon his ability to sense the things
he touches and to appreciate the finest grades of motion made by his
arms and legs. In addition to this high degree of sensing in his hands,
he has also acquired greater capacity for appreciating movements and
postures of his entire body. Unless the chimpanzee had this expanded
department for body and touch senses, it would be impossible for him
to learn many of the performances which he does so skillfully. He also
would be unable to apply this skill under the direction of his masters
or according to the dictates of his own wishes. It is not difficult to
understand, therefore, why all the great departments of the senses have
increased so much in size in the chimpanzee. Obviously, by amplifying
and refining the raw materials received as sense impressions, the
output seen in the chimpanzee’s behaviour has been correspondingly
amplified and extended. The significance of growth in the parietal, the
occipital, and the temporal lobes in this light becomes clear.
One important detail in the superbrain of the chimpanzee we have not
yet considered. It will be recalled that the central groove is one
of the salient landmarks in the brain. Its outstanding importance
arises from the fact that it is the boundary line of the frontal
lobe. All of the territory lying in front of this groove represents
the last acquired department of the superbrain, the one having the
highest authority. It is here that all of the highest brain functions
are located. Judgment and reason are included in this list. But to
these should be added the ability to profit by experience in the
better guidance of life, the upbuilding of personality, and the
proper adjustment in all courses of action requiring initiative,
insight, restraint, and self-control; and, finally, recognition of
responsibility and appreciation of opportunity.
The frontal territory in the chimpanzee is more extensive than in the
orang or any other of the lower apes. It shows an additional amount of
convolution. The frontal coils for producing the brain power of this
highest department have attained a development not far below that of
man. The counterpart of each human convolution is present, the only
difference being that each individual convolution in the chimpanzee is
less complex than in man. These facts about the frontal lobe, which we
must regard as the permanent headquarters of the chief executive of
the superbrain, are in harmony with what Professor Köhler and other
students of animal psychology have told us about the chimpanzee’s
intelligence. Man’s frontal lobe is a highly complex facsimile of the
chimpanzee’s, just as human intelligence is a more complex development
of the higher mental powers.
These improvements in the superbrain are borne out by both the
bridge and the pyramid. The bridge, recognized as a reliable index
of intelligence, has the value of .400 in the chimpanzee, a rating
much above the orang or any of the lower apes already considered. The
pyramid also shows a corresponding increase, having a value of .172,
and thus indicating a greater development in skilled acts and in the
voluntary control over the actions of the body. These two structures
show that the superbrain has, in fact, become a more efficient governor
for the guidance of a larger, a more complex, and a more effective
machine. Every detail in the brain of chimpanzee clearly demonstrates
the marked advance that has been made in the steady upward climb. We
are able to identify all of the chief features characteristic of the
human brain.