_INTELLIGENT BEHAVIOUR_
I.--THE NATURE OF INTELLIGENT BEHAVIOUR
Such an animal as a newly hatched bird or an insect just set free
from the chrysalis is a going concern, a living creature. It is the
bearer of wonderfully complex automatic machinery, capable, under the
initiating influence of stimuli, of performing instinctive acts. But
if this were all we should have no more than a cunningly wrought and
self-developing automatic machine. What the creature does instinctively
at first it would do always, perhaps a little more smoothly as the
organic mechanism settled down to its work--just as a steam-engine goes
more smoothly when it has been running for a while; but otherwise the
action would continue unchanged. Instinctive behaviour would remain
unmodified throughout life. The chick, however, or the imago insect is
something more than this. It affords evidence of the accommodation of
behaviour to varying circumstances. It so acts as to lead us to infer
that there are centres of intelligent control through the action of
which the automatic behaviour can be modified in accordance with the
results of experience. When, for example, a young chick walks towards
and pecks at a ladybird, the like of which he has never before seen,
the behaviour may be purely instinctive; and so, too, when he similarly
seizes a wasp-larva. Even when he rejects the ladybird or swallows the
larva, this may be directly due to unpleasant stimulation in the one
case, and pleasant in the other. But when, after a few trials, the
chick leaves ladybirds unmolested while he seizes wasp-larvæ with
increased energy, he affords evidence of selection based on individual
experience. And such selection implies intelligence in almost its
simplest expression. We may say, therefore, that, whereas instinctive
behaviour is prior to individual experience, intelligent behaviour
is the outcome and product of such experience. This distinction is
presumably clear enough; and it is one that is based on the facts
of observation. But we must not fail to notice that, though the
logical distinction is quite clear, the acquired modifications of
behaviour, which we speak of as intelligent, presuppose congenital
modes of response which are guided to finer issues. We may say,
then, that where these congenital modes of response take the form of
instinctive behaviour, there is supplied a general plan of action
which intelligence particularizes in such a manner as to produce
accommodation to the conditions of existence.
We have already frankly admitted that, in the present state of our
knowledge, we do not know with any definiteness how intelligent
modification of behaviour is effected. But it seems probable that from
all parts of the automatically working organic machine messages come
in to the centres of conscious control, and that in accordance with
the net result of all these messages, and the past experience which
they recall, other messages go out to the automatic centres, and, by
checking their action here and enforcing it there, give new direction
to the resulting behaviour. If this be so, the consciousness associated
with the control-centres is like the person who sits in a central
office and guides the working of some organized system in accordance
with the information he is constantly receiving; who sends messages to
check activity in certain directions and to render it more efficient
and vigorous in others.
It may be said, however, that intelligent guidance is, at any rate
in such simple cases as the selection of a palatable grub and the
rejection of a nauseous ladybird, itself determined by instinctive
likes and dislikes. All young chicks apparently find wasp-larvæ
palatable and ladybirds the reverse; and this is just as much
the outcome of heredity as the instinctive act of pecking. Since,
therefore, heredity determines what shall be selected and what
rejected--since the likes and dislikes are themselves instinctive--any
essential difference between congenital and acquired behaviour seems to
be evanescent.
Now, if we apply to the affective qualities of mental states--the
pleasurable tone or its opposite which characterize such states--the
term “instinctive,” we do so in reference to the broader psychological
conception of instinct, rather than in accordance with the narrower
biological acceptation of the term. For the likes and dislikes
constitute part of the conditions under which the behaviour occurs,
and not elements in the co-ordinated response as such. Hence it is
preferable to apply to these hereditary qualities the term _innate_,
rather than the term _instinctive_. But, waiving this distinction,
it is true that such pleasant or unpleasant qualities of the sensory
results of stimuli are part of the animal’s hereditary outfit, and
are not acquired in the course of individual experience. What, then,
is acquired? What part does experience play in the development of
intelligent behaviour? Let us consider the case of the chick and the
ladybird, and see whether it helps us to answer these questions. The
chick is stimulated to the instinctive pecking response by a small
moving object. That is the first scene of the little drama. In the
second scene the ladybird is seized, sensory centres are unpleasantly
stimulated, and the insect is dropped or thrown on one side with signs
of disgust. Let us grant that this aversion with its characteristic
response is also instinctive. _There is no hereditary connection
between scene 1 and scene 2._ After an interval the curtain rises
on act ii. The characters are the same as in the first scene of the
previous act. But the action of the drama is different. The chick does
not seize the ladybird. Why? Because _there is an acquired connection
between scenes 1 and 2 of the previous act_. The chick has gained
experience of the nauseous character of the insect, and this experience
influences and modifies his behaviour. The essentially new feature,
therefore, is the establishment of a connection which is not provided
through inheritance. To put the distinction in a brief form, we may
say that instinct depends on how the nervous system is built through
heredity; while intelligence depends upon how the nervous system is
developed through use.
Assuming that an animal is capable of gaining experience and of
acquiring new nervous connections in the course of individual
experience, it follows that, as has already been indicated,
instinctive behaviour in its logical purity is only presented in
the first performance of any given co-ordinated act. For after this
the animal has gained experience of its performance; and this can
no longer conform to a definition of instinct, according to which
it is characterized as “prior to experience.” On the other hand,
intelligent behaviour cannot be presented on the first occurrence of
any action, since there is no prior experience thereof in the light
of which it may be guided. This logical distinction may be expressed
by saying that instinctive behaviour is always prior to experience,
while intelligent behaviour is always subsequent to experience. When,
however, instinctive procedure continues throughout life practically
unmodified or but little modified, we may still class it under
instinct, since the hereditary connections are still the predominant
factors. And where the latter part of an instinctive sequence is
modified by the experience gained in the former part, we may still term
the modification intelligent, however small may be the time-interval
implied in the word “subsequent.” Sharp as the logical distinction is,
the behaviour of animals is in the main a joint-product, and whether we
term it instinctive or intelligent depends upon whether the hereditary
or the acquired factor predominates.
Passing on now to consider some further characteristics of intelligent
behaviour, we may first notice what Dr. Charles Mercier, in his
work on “The Nervous System and the Mind,” terms the four criteria
of intelligence. Intelligence is manifested, he says, first in the
novelty of the adjustments to external circumstances; secondly, in the
complexity; thirdly in the precision; and fourthly, in dealing with
the circumstances in such a way as to extract from them the maximum of
benefit.
[Illustration: FIG. 18.--Leaf-case of Birch-weevil.]
If, however, we are to regard these severally as criteria of
intelligence, each should serve to differentiate intelligent from
instinctive behaviour. But this is not the case. The precision of the
adjustment cannot be regarded as a criterion of intelligence, for many
instinctive acts are remarkably precise. No grocer’s assistant rolls a
paper funnel with more precision than is displayed by the birch-weevil
(_Rhynchites betulæ_) in constructing the leaf-case in which her eggs
are laid. Curved incisions of constant form are made on either side of
the midrib, and are “of just the right shape to make the overlaps in
the rolling, and to retain them rolled up with the least tendency to
spring back,”[49] while the tip of the leaf is rolled into a second
smaller funnel, which is tucked in to close the opening of the first,
after the eggs have been deposited. “The eggs hatch in their dark
place, each giving rise to an eyeless maggot, which ultimately leaves
the funnel for the earth.... Hence the beetle cannot be considered
to have ever seen a funnel, and certainly has never witnessed the
construction of one, though, when disclosed, it almost immediately
sets to work to make funnels on the complex and perfect system”
characteristic of the species. This is but one example of instinctive
precision out of the many which could be cited. We may say, then,
that though, when an act is otherwise shown to be intelligent, the
precision is a criterion of the level attained by the intelligence,
still it cannot be said to be a criterion which serves to distinguish
intelligent from instinctive behaviour.
Nor can we regard apparent prevision (which is sometimes advanced as
a criterion of intelligence) as specially distinctive of intelligent
acts regarded objectively in the study of animal behaviour. For, as we
have had occasion to show, there are many instincts which display an
astonishing amount of what may be termed “blind prevision”--instance
the instinctive regard for the welfare of unborn offspring which the
mother will never see, and the instinctive preparation for an unknown
future existence in the case of insect larvæ.
Nor, again, is the complexity of the adjustment distinctive of
intelligence as contrasted with instinct. We have cited examples
which afford evidence of much complexity in instinctive behaviour.
The construction and storage of the nest among solitary wasps, and
their methods of capturing and conveying the insects or spiders on
which they prey, are sufficiently complex. So, too, is the behaviour
of the Sitaris larva which attaches itself to the male bee, passes to
the female, and then slips on to the eggs she lays; and so, again,
is that of the Yucca moth, which collects pollen from the anthers,
conveys it to the stigma, and then lays her eggs among the ovules.
These cases show, too, that the circumstances may be dealt with in
such a way as to extract from them the maximum of benefit. It would be
difficult intelligently to improve upon the manner of dealing with the
circumstances displayed in many familiar modes of instinctive procedure.
There remain the novelty of the adjustment and the individuality
displayed. And here we seem to have valid criteria of intelligent
behaviour. The ability to perform acts in special adaptation to
new circumstances, and the individuality manifested in dealing with
the complex conditions of a variable environment,--these seem to be
distinctive features of intelligence. On the other hand, in instinctive
behaviour there seems to be no choice; the animal is impelled to their
stereotyped performance through impulse, as by a stern necessity; they
are so far from novel that they are performed by every like individual
of the species, and have been so performed by their ancestors for
generations; and in performing the instinctive act, the animal seems to
have no more individuality or originality than a piece of adequately
wound clockwork.
Granting, then, that behaviour is shown to be intelligent by the fact
that there is evidence of profiting by experience, we may say that
the level attained by the intelligence is indicated by the complexity
of the adjustment, its precision, the individuality shown, the amount
of prevision disclosed, and in its being such as to extract from the
circumstances the maximum of benefit. Many of these points, however,
serve equally well to mark the level of instinctive procedure.
II.--INTELLIGENT BEHAVIOUR IN INSECTS
It is, as we have seen, among the higher invertebrates, especially in
insects, that some of the most remarkable and complex instincts may be
found. There is,[50] however, a tendency to ascribe the behaviour of
insects entirely to instinct, without sufficient evidence that neither
imitation, instruction, nor intelligent learning play any part. This
is, perhaps, a survival of the old-fashioned view that all the acts
of the lower animals are performed from instinct, whereas those of
human beings are to be regarded as rational or intelligent. In popular
writings and lectures, for example, we frequently find some or all of
the following activities of ant-life ascribed to instinct: recognition
of members of the same nest; powers of communication; keeping aphides
for the sake of their sweet secretion; collection of aphid eggs in
October, hatching them out in the nest, and taking them in the spring
to the daisies, on which they feed, for pasture; slave-making and
slave-keeping, which, in some cases, is so ancient a habit that the
enslavers are unable even to feed themselves; keeping insects as beasts
of burden, _e.g._ a kind of plant-bug to carry leaves; keeping beetles,
etc., as domestic pets; habits of personal cleanliness, one ant giving
another a brush-up, and being brushed-up in return; habits of play
and recreation; habits of burying the dead; the storage of grain and
nipping the budding rootlet to prevent further germination; the habits
described by Dr. Lincecum, and to a large extent confirmed by Dr.
McCook, that Texan ants prepare a clearing around their nest, and six
months later harvest the ant-rice, a kind of grass of which they are
particularly fond, even, according to Lincecum, seeking and sowing the
grain which shall yield this harvest; the collection by other ants of
grass to manure the soil on which there subsequently grows a species of
fungus upon which they feed; the military organization of the ecitons
of Central America; and so forth. Now, the description of the habits
of ants forms one of the most interesting chapters in natural history.
But to class them all as illustrations of instinct is a survival of an
old-fashioned method of treatment.
To put the matter in another way. Suppose that an intelligent ant
were to make observations on human behaviour as displayed in one of
our great cities or in an agricultural district. Seeing so great an
amount of routine work going on around him, might he not be in danger
of regarding all this as evidence of hereditary instinct? Might he not
find it difficult to obtain satisfactory evidence of the establishment
of our habits, of the fact that this routine work has to some extent
to be learnt? Might he not say (perhaps not wholly without truth), “I
can see nothing whatever in the training of the children of these men
to fit them for their life-work. The training of their children has no
more apparent bearing upon the activities of their after-life than
the feeding of our grubs has on the duties of ant-life. And although
we must remember,” he might continue, “that these large animals do not
have the advantage which we possess of awaking suddenly, as by a new
birth, to their full faculties, still, as they grow older, now one and
now another of their deferred instincts is unfolded and manifested.
They fall into the routine of life with little or no training as
the period proper to the various instincts arrives. If learning
thereof there be, it has at present escaped our observation. And such
intelligence as their activities evince (and many of them do show
remarkable adaptation to uniform conditions of life) would seem to be
rather ancestral than of the present time; as is shown by the fact that
many of the adaptations are directed rather to past conditions of life
than to those which now hold good. In the presence of new emergencies
to which their instincts have not fitted them, these poor men are often
completely at a loss. We cannot but conclude, therefore, that, although
shown under somewhat different and less favourable conditions, instinct
occupies fully as large a space in the psychology of man as it does in
that of the ant, while their intelligence is far less unerring and,
therefore, markedly inferior to our own.”
Of course, the views here attributed to the ant are very absurd. But
are they much more absurd than the views of those who, on the evidence
which we at present possess, attribute all the varied activities of
ant-life to instinct? Take the case of the ecitons, or military ants,
or the harvesting ants, or the ants that are said to keep draught-bugs
as beasts of burden: have we sufficient evidence to enable us to
affirm that these modes of behaviour are purely instinctive and not
intelligent; that all the varied manœuvres of the military ants, for
example, are displayed to the full without any learning or imitation,
without teaching and without intelligence on the part of every
individual in the army.
That in some cases there is something very like a training or education
of the ant when it emerges from the pupa condition is rendered probable
by the observations of M. Forel. As Romanes says,[51] “The young
ant does not appear to come into the world with a full instinctive
knowledge of all its duties as a member of a social community. It is
led about the nest and ‘trained to a knowledge of domestic duties,
especially in the case of larvæ.’ Later on, the young ants are taught
to distinguish between friends and foes.”
We have only to weigh the evidence brought forward by such observers
as Fabre and Dr. Peckham to see that among the solitary wasps and
mason bees the behaviour, though founded on instinct, is in large
degree modified by intelligence. The care with which a site for the
tunnelled nest in the ground is selected, betokens something more
than instinct. The following is a slightly condensed statement of Dr.
and Mrs. Peckham’s observations on one of the solitary wasps (_Aporus
fasciatus_).[52] “We were working one day in the melon-field when we
saw one of these little wasps going backwards and dragging a spider.
She twice left it on the ground while she circled about for a moment,
but soon carried it up on to one of the large melon leaves, and left
it there while she made a long and careful study of the locality,
skimming close to the ground in and out among the vines; at length she
went under a leaf close to the ground, and began to dig. After her head
was well down in the ground we broke off the leaf that we might see
her method of work. She went on for ten minutes without noticing the
change, and then, without any circling, flew off to visit her spider.
When she tried to return to her hole it was evident that some landmark
was missing. Again and again she zig-zagged from the spider to the
nesting-place, going by a sort of path among the vines from leaf to
leaf, and from blossom to blossom, but when she reached the spot she
did not recognize it. At last we laid the leaf back in its place over
the opening, when she at once went in and resumed her work, keeping
at it steadily for ten minutes longer. At this point she suddenly
reversed her operations, and began to fill in the hole that she had
made. She then glanced at the spider, selected a new place, and began
to dig again. This hole was also filled in; she looked once more at
the spider, and started a nest in a new place. This, in turn, was soon
abandoned, as was a fourth. The fifth beginning was made under a leaf
that lay close to the ground, but after twenty minutes’ work this place
also was abandoned and a sixth started. This, however, was the final
choice, and after forty-five minutes spent in digging it was completed.”
[Illustration: FIG. 19.--Solitary Wasp using a stone to beat down the
earth over its nest (after Peckham).]
This description shows an amount of apparent fastidiousness which
is quite irreconcilable with the hypothesis that the behaviour
is merely instinctive. Not less fastidious are some wasps in the
temporary closure of the hole with a stone or pellet of earth,
the operation being repeated several times with different covers
before the insect seems to be satisfied; while in other cases the
hole is hidden by bringing earth in such quantity as to render the
place indistinguishable from the rest of the field. But in one case
observed by Dr. Peckham, intelligent procedure was carried so far as
apparently to involve the use of a tool, the same behaviour having been
independently observed in the same genus (_Ammophila_) by Dr. S. W.
Williston of Kansas University. “Just here,” writes Dr. Peckham,[53]
“must be told the story of one little wasp whose individuality stands
out in our minds more distinctly than that of any of the others. In
filling up her nest she put her head down into it and bit away the
loose earth from the sides, letting it fall to the bottom of the
burrow, and then, after a quantity had accumulated, jammed it down with
her head. Earth was then brought from the outside and pressed in, and
then more was bitten from the sides. When, at last, the filling was
level with the ground, she brought a quantity of fine grains of dirt
to the spot, and, picking up a small pebble in her mandibles, used
it as a hammer in pounding them down with rapid strokes, thus making
this spot as hard and firm as the surrounding surface. Before we could
recover from our astonishment at this performance she had dropped her
stone and was bringing more earth, and in a moment we saw her pick up
the pebble and again pound the earth into place with it. Once more the
whole process was repeated, and then the little creature flew away.”
Here we have intelligent behaviour rising to a level to which some
would apply the term rational. For the act may be held to afford
evidence of the perception of the relation of the means employed to
an end to be attained, and some general conception of purpose. In
this section, which deals with description of behaviour based on
observation, the psychological explanation cannot be discussed. Similar
indications of deliberate action may be held to be afforded by the
sometimes elaborate “locality studies” which these insects seem to
make,--by the “care that is taken by wasps to acquaint themselves with
the surroundings of their nests.” A _Sphex_, for example, which had
partially made and then abandoned several nests, left them without any
locality study; but when she had completed a nest in a suitable spot
she made “a most thorough and systematic study of the surroundings.
She flew in and out among the plants, first in narrow circles near
the surface of the ground, and then in wider and wider ones as she
rose higher in the air, until at last she took a straight line and
disappeared in the distance.” Another species (_Cerceris deserta_) “has
the habit of making a number of half circles in front of the nest, and
then, after rising a little higher, of flying several times completely
round it.” The method of procedure is, it seems, so normal to the
species that it is probably founded on an instinctive basis. Dr. and
Mrs. Peckham, in commenting on their observations, say:[54] “If the
examination of the objects about the nest makes no impression upon the
wasp, or if it is not remembered, she ought not to be inconvenienced
nor thrown off her track when weeds and stones are removed and
the surface of the ground is smoothed over; but this is just what
happens.” For convenience of observation they “sometimes gently moved
intercepting objects to one side, but even such a slight change threw
the wasp out of her bearings, and made it difficult for her to recover
her treasure.” Where wasps form a number of nests in a small plot of
ground, as in the case of _Bembex_, each knows and returns to its own
hole, as was proved by Dr. Peckham, who marked the insects and their
nests with paint.
So, too, with regard to prey. In the course of his observations on
_Pompilus_, Fabre removed the spider which the wasp had deposited on
a tuft of vegetation before she made her nest. As she was at work
beneath the surface she could not see what went on above ground or
where the spider had been redeposited some twenty inches from its
former position. On emerging from the nest the wasp went straight to
the original spot, searched round it for some time, then made further
excursions, and discovered the spider. After slightly altering its
position, and placing it on another tuft of vegetation, she returned to
her subterranean labours, giving the observer an opportunity of again
moving the spider. Five times did Fabre repeat the operation, and every
time the wasp returned to the spot where she had last deposited her
prey.
The same observer records some interesting experiments with the mason
bee, _Chalicodoma_. The mud nests of the species investigated were
affixed to stones on the banks of the Rhone. When a nest was partially
constructed, the bee having flown off for more material, Fabre moved
the stone to a new position, near at hand and easily visible from the
original site. The bee went straight to the place where the nest had
been, searched the immediate neighbourhood, flew off, and returned
to the same spot to continue the search. If she came across her own
nest in its new position she did not recognize it as hers, but left it
after examination. But if a stone with the nest of another bee in about
the same stage of construction was placed in the position occupied
by her own, she adopted it. And when two nests near together, both
half built, were transposed, each bee unhesitatingly adopted the nest
which occupied the position where its own nest had been. It may well
seem strange that, the general locality-memory being so well marked,
the recognition of the particular stone and nest should be deficient.
This may be due to the fact that the so-called compound eyes are
the organs concerned in locality vision, while the ocelli deal with
details at very close range, and that the former alone afford the
requisite data for recognition; by their instrumentality alone arises
the conscious situation which affords guidance in behaviour. And in
that situation slight changes which for us make it “still the same but
with a difference” render it no longer the same for a being of more
limited intelligence--one probably incapable of analyzing the situation
and seeing that the sameness preponderates over the difference. Be
this as it may, the failure of a bee to recognize its own nest under
circumstances so foreign to its experience as removal to a new spot may
be paralleled with what I have observed in the case of sticklebacks.
A nest had been built in a round glass bell jar which stood near a
window. Some aquatic vegetation grew in the tank, and the nest was
built on the window side. An experiment was made by turning the large
bell jar through a right angle. The male stickleback searched for its
nest in the old direction on the window side--that is to say, the
same position in reference to the incidence of the light. The search
was, of course, fruitless, and a new nest was begun in this position.
Presently the old nest was discovered, and was then vigorously
destroyed in just the same way as the nest of a rival is pulled to
pieces and scattered. Here a new incidence of light and new direction
of shadows seemed to have completely transformed the visual situation.
To return to insects, it is probable that the homing faculty is not
the result of an inborn mysterious instinct dependent on some sense of
direction of which we have no knowledge, but is based upon experience
gained during their flight hither and thither--that, in a word, it is
intelligent and not instinctive. Experiments of Fabre at first seemed
to suggest some magnetic influence to which bees were sensitive; for
when a minute magnet was fixed to a bee as it started on its return
journey, the insect was at fault; but as a check experiment he affixed
a piece of straw instead of a magnet, with similar results. Some of
Fabre’s observations and those of Dr. Bethe[55] are difficult to
reconcile with the hypothesis that, in the homing, guidance is due to
acquired acquaintance with the locality. But, on the other hand, the
experiments of Lord Avebury and of Romanes seem to favour this view.
Romanes found that when bees were taken inland from their hive near
the seaboard, and then liberated, they returned from considerable
distances, the whole locality being familiar; but taken to the
seashore, where the objects around them were unfamiliar (since the
seashore is not the place where flowers and nectar are to be found),
the bees, though not far distant from the hive, were nonplussed and
lost their way. Dr. and Mrs. Peckham, as the result of their extremely
careful observations, seem to have no doubt that the homing of solitary
wasps is due to locality-experience; and of the social wasp, _Polistes
fusca_, they say:[56] “We have seen the young workers make repeated
locality studies when they first began to venture away from home, but
as they occupy the same nest all summer they, of course, grow more and
more familiar with their surroundings, until they become so thoroughly
acquainted with them that they can find their way without the least
difficulty. We have no doubt that with them, as with the solitary
wasps, the faculty is not instinctive, but is the direct outcome of
individual experience.”
In the interesting pages of the works in which Dr. and Mrs. Peckham
describe their investigations, there are many observations which show
that wasps are capable of intelligently profiting by the experience
which their instinctive behaviour places them in a position to acquire.
The inherited tendencies and aptitudes pave the way for acquired
modification and accommodation of behaviour. To catch and paralyze
spiders, to dig and prepare a tunnelled nest, and to carry the prey
to the nest, all this affords the instinctive basis; but when the
observers tell us that they “have several times seen wasps enlarge
their holes when a trial had demonstrated that a spider would not go
in,” and even on one occasion without trial when an unusually bulky
spider was brought, there is something beyond instinct; there is
intelligent adjustment to special circumstances given in experience.
Presumably intelligent is the habit frequently observed in one species
of _Pompilus_, and occasionally in another, of hanging the paralyzed
spider in a crotch of a branching stem, usually of bean or sorrel,
where it will be safe from the depredation of ants. On one occasion
Dr. Peckham, desirous of seeing the exact manner in which the victim
was stung, substituted an unhurt spider for that which the wasp had
paralyzed.[57] “According to the habit of its species when danger
threatens, it kept perfectly quiet, and when the wasp returned it was
hanging there as motionless as a piece of dead matter; but she would
not touch it; she hunted all over that plant and then over several
others near to it, returning continually to look again at the right
spot. After five minutes she flew off in the direction of the woods
to catch another spider. Why did she go to the woods? Why did she
not take the one that hung there in plain view? It could not have
been due to the fact that we had handled the spider, since when, on
other occasions, we took one that had been paralyzed, examined it, and
then returned it to the wasp, she accepted it without hesitation....
In forty minutes she came back with another spider, but, instead of
taking it into the nest, she hung it upon a bean plant near by, and
then proceeded to dig a new hole a few inches distant from the first.
Foolish little wasp, what a waste of labour! Truly, if you are endowed
with energy beyond your fellows, you are but meagrely furnished with
reason.”
[Illustration: FIG. 20.--Spiders placed by Solitary Wasps in the
crotches of branching stems (after Peckham).]
Here we have the routine of instinct--the normal mode of hunting and
capturing prey, the normal procedure of bringing the spider, and
then making the nest, predominating over any tendency to initiate
intelligent improvements. This, however, should not surprise us, in
whom the force of habit is often so strong. Nor should we feel surprise
at the apparently stupid tolerance some of these wasps display in
presence of parasites. _Bembex_, which does not store and close its
cell, but brings continual supplies of food to its larvæ, is not
disturbed by the presence in the cell of the grubs of the parasitic
fly _Miltogramma_. She could, we think, easily free her nest of these
intruders, but she continues to bring supplies, though the parasites
may absorb it all and leave her own larvæ to perish. She adapts her
procedure to the new conditions, being incapable of knowing that she is
feeding the enemies of her race.
Enough has now been said to show the extent and the limitations of the
intelligence of such insects as the solitary wasps. It will be noticed
that the acquired modifications of behaviour occur in close connection
with the inherited ground-plan of instinctive procedure. We shall
have occasion to note the same connection in our discussion of social
behaviour in the next chapter. And we shall consider the influence of
intelligence on instinct before we bring this chapter to a close.
III.--SOME RESULTS OF EXPERIMENT
It is unnecessary to give a _resumé_ of entertaining anecdotes
illustrative of intelligent behaviour in the higher animals. Such
anecdotes are too often the outcome of casual observations by untrained
observers; and the interpretation put upon the facts frequently shows
a want of psychological discrimination. Such is not the material of
which science is constituted. What is needed is systematic observation
conducted, so far as possible, under controlled conditions. Two
things are necessary: first, to distinguish instinctive behaviour,
inherited as such, from the acquired modifications or new departures
due to intelligence; and secondly, to determine the method and range
of intelligent procedure. These problems can only be solved in their
entirety by a complete knowledge of the life-history of the animal
concerned. But they may be attacked in detail by a systematic study
of particular modes of behaviour, and by an investigation into
their manner of origin. That this may be done with some approach
to accuracy, resort must be had to experiment, which permits of
observation under controlled conditions.
To ascertain, for example, how far nest-building is instinctive in
birds, Mr. John S. Budgett hatched a hen greenfinch under a canary. In
the following autumn he bought a caged bird, a cock, probably of the
same year, and in the succeeding spring turned the pair into a large
aviary, supplying such material as twigs, rootlets, dried grass, moss,
feathers, sheep’s wool and horsehair. The hen soon began to build, the
cock bird taking no share in the work, and finished her nest in a few
days. On careful comparison it was found to resemble that of a wild
greenfinch in every particular, being made of wool, roots, and moss,
lined with horsehair. A second nest the aviary greenfinch built was
also quite normal.
In the case of a bullfinch which Mr. Budgett reared, having obtained it
when a few weeks’ old, the first nest was composed of dried grass with
a little wool and hair, but without either rootlets or twigs. A second
which she built was, however, quite typical, made of fine twigs and
roots, and lined with horsehair; as was also a third nest.
It is just possible, though most improbable, that the bullfinch
utilized its three weeks’ experience gained in the nest from which it
was taken. But Mr. Jenner Weir describes[58] observations on canaries
in which this source of experience is excluded. “It is usual,” he
says, “with canary fanciers to take out the nest constructed by the
parent birds, and to place a felt nest in its place, and when her young
are hatched, and old enough to be handled, to place a second clean
nest, also of felt, in the box, removing the other. But I never knew
that canaries so reared failed to make a nest when the breeding time
arrived. I have, on the other hand, marvelled to see how like a wild
bird’s the nests are constructed. It is customary to supply them with
a small set of materials, such as moss and hair. They use the moss for
the foundation, and line with the finer materials, just as a wild
goldfinch would do.”
Experiment seems, therefore, to show in a way, and with a clearness
impossible of attainment by observation under natural uncontrolled
conditions, that nest-building in birds is instinctive. That the manner
and method of procedure is often modified in accordance with special
conditions--that the instinctive outline of nidification receives
its final touches through individual experience--is sometimes seen
under nature, and more often under the semi-experimental conditions
of domestication. Thus three pairs of pigeons in the Wilson Tower
of Clifton College made their nests in 1898, as I am informed by
Mr. H. C. Playne, of galvanized iron wire, pieces of which were
left in a corner at the top of the tower, thus affording a parallel
to the behaviour of the unconventional crow of Calcutta, mentioned
by Mr. F. W. Headley,[59] which made its nest of soda-water bottle
wires, which it picked up in a back yard. But even in this matter
experiment serves to bring out clearly the selective influence which
is exercised by intelligence. Bolton,[60] in 1792, observed a pair of
goldfinches beginning to build their nest in his garden. They formed
the ground-work of moss, grass, etc., as usual; but on his scattering
small parcels of wool in different parts of the garden they, in great
measure, left off the use of their own stuff and used the wool.
Afterwards he gave them cotton, and they then used this instead of the
wool; then he supplied fine down, and they finished their work with
this, leaving the wool and cotton.
In studying the behaviour of wild animals under natural conditions, it
must always be difficult to distinguish the congenital basis from the
acquired elements; for both tend to bring about a working adjustment
to the conditions of life, and we can seldom have opportunities of
tracing the interplay of the factors which produce the instinct-habits
of adult life. But under domestication we seek to bring about a new
working adjustment to conditions imposed by man. The skilful trainer
utilizes the natural instinctive tendencies as a basis; and, by a
system of rewards and punishments, leads the intelligent modifications
of behaviour along lines directed by his deliberate purpose. The
conditions are largely those of experiment, and they bring out the
play and range of intelligence in a way which would otherwise elude
our observation. The training of falcons for the chase affords a good
illustration, since they cannot be bred in confinement, and the effects
of training cannot therefore be hereditary. The falconer’s object is
to modify the congenital instinctive behaviour of a bird of prey for
the purposes of sport. She is trained to the lure at first at short
distances, and step by step through longer flights; she is taught by
snatching away the lure to stoop at it repeatedly as often as it is
jerked aside; and then she is trained on living quarry, at first under
easy conditions, till eventually she can be flown at a wild bird. And
as a result a well-trained falcon will follow her master from field
to field, regulating her flight by his movements, always ready for a
stoop when the quarry is sprung. The fact that she can be thus educated
for her work shows that her behaviour is plastic, and can be moulded
by intelligence. Experimental conditions reveal the fact; but under
nature the moulding influence of intelligence is presumably not less
important, though it is more directly in line with the congenital
instinctive tendencies.
That much of the behaviour of the higher animals is guided by
experience similar to that which plays so large a part in their
training under the experimental conditions of domestication is
generally admitted. But what are the range and limits of animal
intelligence, and whether it attains the level of rational conduct,
in the restricted sense of the term “rational,” are questions open to
discussion, to which answers are more likely to be obtained through
experiment than by chance observations.
Before giving some of the results of such experiment it will be well
to revert to the distinction, which was drawn in the second chapter,
between the lower or intelligent stage of mental development and the
higher or rational stage. It will be remembered that rational processes
were characterized by the fact that the situations contain the products
of reflective thought, presumably absent in the earlier stages of
development; that they were further characterized by a new purpose or
end of consciousness, namely, to explain the situations which at an
earlier stage are merely accepted as they are given in presentation or
re-presentation; they require deliberate attention to the relationships
which hold good among the several elements of successive situations;
and they involve, so far as behaviour is concerned, the intentional
application of an ideal scheme with the object of rational guidance.
On the other hand, the animal at the stage of intelligent behaviour
deals with the circumstances of his comparatively simple life by
making use of the particular situations which have been presented to
consciousness in the course of his practical experience. If such an
animal be placed in the midst of new circumstances he has to find out
by a process of trial and error how they are to be met. After a longer
or shorter period of trial, guided only by particular experiences,
he chances to hit upon a mode of procedure which is successful. The
successful act is then incorporated in a new situation; at first,
perhaps, only incompletely. The association is eventually established
by repetition, through which is acquired the habit of doing the right
thing in the appropriate manner. Why he does this and not something
else, in so far as he is intelligent and not rational, he probably
neither knows nor has the wit to consider. The satisfaction of success
suffices for intelligence as such. If the circumstances be so modified
as to render the particular mode of meeting them ineffectual, after
trying again and again in the old way, he will sometimes stumble upon
the proper mode of overcoming the difficulty, and after doing so two
or three times a new conscious situation involving the requisite
associations will be established, and the appropriate behaviour will
become habitual. But why this new mode of procedure rather than any
other is adopted, intelligence as such does not know, because it does
not analyze the situation and disentangle the essential relationships.
The satisfaction of success again suffices. In a word, such an animal
in the perceptual stage of mental development seems wanting in the
power of reflection. He does not appear to show evidence of framing
anything like a general scheme of knowledge which he can apply to the
solution of particular problems, of a practical nature, involving
difficulties and obstacles.
The method of intelligence--in the sense in which we are using this
term--the method of varied trial and error with the utilization of
chance success, is a lengthy and somewhat clumsy process; but it
suffices. Now contrast it with the procedure of a rational animal, such
as man is or may be. When he is confronted by a difficulty he is not
content to meet it by trying this way, and that way, and another way,
anyhow, and trusting to chance to bring success, but he considers the
problem in all its relations with a view to ascertaining the essential
nature of the difficulty. For each attempted mode of meeting the case
he has a definite reason. He knows why he does this and not that. He
has a plan or scheme which he puts into execution. And if it fail,
he is not content till he finds out wherein the failure lay. This
enables him to plan a better scheme. He sees why it is better; and if
at last he be successful by a happy hit, as in the chance procedure
of intelligence, he looks for the reason of it. And seeing why this
fortunate attempt, unlike his previous efforts, just meets the case,
he repeats it because he perceives that herein lies the essential
solution of the difficulty. Both in the case of intelligence and in
that of reason, as here distinguished, present procedure is based upon
past experience; but reason has built upon the foundations thus laid an
orderly scheme, and knows its whys and wherefores, while intelligence
is at the mercy of chance associations. The reason for success it has
not the wit to assign.
The essential difference between the two cases may be put in another
way by saying that the intelligent being forms sensory impressions and
sensory images linked together by bonds of association, combining and
coalescing to constitute a conscious situation effective in behaviour
under the guiding influence of pleasure and pain; while the rational
being not only does all this, but goes further. He fixes his attention
on the way in which the elements in the situation are connected and
related; he builds an ideal framework on which the sensory impressions
are set or move in an orderly manner. And it is this scheme, fashioned
by reason and transforming the situation, which he utilizes in dealing
with difficulties.
Yet another way of putting the same essential distinction is to say
that intelligence deals with pictures, either directly presented to
the senses or called up in re-presentation. If we state the matter
thus, however, we must remember that the “pictures” may be painted in
colours supplied by any of the senses; and that smells, tastes, sounds,
touches, pressures, limb-movements, and so forth, are elements in the
pictured product. Bearing this in mind, we may say that intelligence
deals with sensory impressions and their revived images in concrete
and particular situations; while reason analyzes the pictures, and
extracts from them general notions in terms of which the pictures may
be explained. For example, we picture a stone falling to the earth;
but we explain it by the general notion of gravitative attraction. The
conception forms part of our ideal scheme of knowledge, which is not
itself picturable, though this or that example of its action may be
presented or re-presented in sensory imagery.
Once more we may say--and this way of looking at the question arises
naturally out of what has gone before--that intelligence deals with
concrete examples, and does not rise to the abstract and general
rule. The ideal scheme of reason is the result of abstraction and
generalization. It is a framework of conceptions which can be applied
to the particular facts which fall under observation to see whether
it fits and meets the case. Intelligence has to deal with the facts
as they present themselves, without the aid of an organized system of
knowledge built up into an ideal scheme.
Enough has now been said to indicate the distinction between the
method of intelligence and that of reason. It may, no doubt, be said
that the terminology used is open to criticism; for, on the one hand,
the words “intelligence” and “intelligent” are frequently used as
synonymous with “reason” and “rational;” and, on the other hand, acts
requiring neither abstraction, generalization, nor the application
of any scheme of knowledge are frequently spoken of as “rational.”
Hence there is, it may be urged, some danger of misunderstanding. This
may be granted. And unless some such restriction of meaning under
suitable terms be accepted by psychologists, misunderstanding will
continue. More essential, however, than the distinctive terms we are
to use is the distinction of method which underlies them. That, I
trust, is sound. Dr. Lindley, in an interesting paper on “A Study of
Puzzles,”[61] has utilized the distinction in his investigation of the
mental development of children, and has found that the procedure of
young children is predominantly of the “sense-trial and error” order
which has above been termed intelligent; and he expresses the opinion
that “most of the adaptations of animals are on this sense-trial and
error level.”
Such certainly seems to be the conclusion to be drawn from my own
experimental observations on dogs. It has frequently been asserted
that the behaviour of a dog with a stick in his mouth, when he comes
to a narrow gap, shows that he at once perceives the nature of
the difficulty, and meets it in a rational manner by adopting the
appropriate plan of action. He pulls the stick through by one end. But
experiments, which I have elsewhere described,[62] showed that a fox
terrier, fourteen months old, seemed to be incapable of perceiving
the nature of the difficulty which vertical iron railings presented
to his passage with a stick in his mouth, and only imperfectly learnt
to overcome it after many ineffectual trials and many failures. The
results obtained on the first afternoon may be quoted to indicate the
nature of the evidence. The dog was sent after a short stick into a
field, and had to pass through vertical rails about six inches apart.
On his return the stick caught at the ends. I whistled and turned as
if to leave; and the dog pushed and struggled vigorously. He then
retired into the field, lay down, and began gnawing the stick, but,
when called, came slowly up to the railings and stuck again. After some
efforts he put his head on one side, and brought the stick, a short
one, through. After patting and encouraging him, I sent him after it
again. On his return he came up to the railings with more confidence,
but, holding the stick by the middle, found his passage barred. After
some struggles he dropped it and came through without it. Sent after it
again, he put his head through the railings, seized the stick by the
middle, and then pulled with all his might, dancing up and down in his
endeavours to effect a passage. Turning his head in his efforts, he
at last brought the stick through. A third time he was again foiled;
again dropped the stick; and again seizing it by the middle tried to
pull it through. I then placed the stick so that he could easily seize
it by one end and draw it through the opening between the rails. But
when I sent him after it, he went through into the field, picked up the
stick by the middle, and tried to push his way between the railings,
succeeding, after many abortive attempts, by holding his head on one
side.
Subsequent trials on many occasions yielded similar results. But the
following summer, when I resumed the experiments, I was able with some
guidance to teach him to bring a long stick to the railings, drop
it, and then draw the stick through by one end; though even then,
if he had dropped it so that one end just caught a rail, he often
failed, shaking his head vigorously, dropping the stick and seizing
it again, and repeating this behaviour until it chanced to fall in
a more favourable position. He did not apparently perceive that by
gently moving the stick a little one way or other the difficulty
could be simply overcome with little effort. Nor when given a crooked
stick, which caught in a rail, did he show any sign of perceiving that
by pushing the stick and freeing the crook he could pull the stick
through. Each time the crook caught he pulled with all his strength,
seizing the stick now at the end, now in the middle, and now near the
crook. At length he seized the crook itself, and with a wrench broke
it off. A man who was passing, and who had paused for a couple of
minutes to watch the proceedings, said, “Clever dog that, sir; he knows
where the hitch do lie.” The remark was the characteristic outcome of
two minutes’ chance observation. During the half hour or more during
which I had watched the dog he had tried nearly every possible way of
holding and tugging at the stick. Such is the mode of behaviour based
on intelligence--continued trial and failure, until a happy effect is
reached, not by methodically planning, but by chance.
Two of my friends criticized these results, and said that they only
showed how stupid _my_ dog was. _Their_ dogs would have acted very
differently. I suggested that the question could easily be put to the
test of experiment. The behaviour of the dog was in each case--the
one a very intelligent Yorkshire terrier, the other an English
terrier--similar to that above described. The owner of the latter was
somewhat annoyed, used forcible language, and told the dog that he
could do it perfectly well if he tried.
In experimenting with my fox terrier on the method adopted in seizing
and carrying differently balanced objects, I used (1) a straight
stick, the centre of gravity of which was at the middle; (2) a Kaffir
knob-kerrie, the centre of gravity of which was about six inches from
the knob; (3) a light geological hammer; and (4) a heavier hammer. In
the last, the centre of balance was close to the hammer head. The net
result of the observations was that the best place for seizing and
holding the object was hit upon in each case after indefinite trials;
that after three or four days’ continuous experience with one (say the
knob-kerrie), another (say the stick) was at first seized nearer one
end, showing the influence of the more recent association; and that
there was little indication of the dog’s seizing any one of the four
at once in the right place, that is to say, the point of seizure was
not clearly differentiated in accordance with the look of the object. I
tied a piece of string, in later trials, round the centre of balance,
but this, at the time of the dog’s death, had not served as a sure
guide to his experience.
The way in which my dog learnt to lift the latch of the garden gate,
and thus let himself out, affords a good example of intelligent
behaviour. The iron gate outside my house is held to by a latch, but
swings open by its own weight if the latch be lifted. Whenever he
wanted to go out the fox terrier raised the latch with the back of his
head, and thus released the gate, which swung open. Now the question in
any such case is: How did he learn the trick? In this particular case
the question can be answered, because he was carefully watched. When
he was put outside the door, he naturally wanted to get out into the
road, where there was much to tempt him--the chance of a run, other
dogs to sniff at, possibly cats to be worried. He gazed eagerly out
through the railings on the low parapet wall shown in the illustration;
and in due time chanced to gaze out under the latch, lifting it
with his head. He withdrew his head and looked out elsewhere; but
the gate had swung open. Here was the fortunate occurrence arising
out of natural tendencies in a dog. But the association between
looking out just there and the open gate with a free passage into the
road is somewhat indirect. The coalescence of the presentative and
re-presentative elements into a conscious situation effective for the
guidance of behaviour was not effected at once. After some ten or
twelve experiences, in each of which the exit was more rapidly effected
with less gazing out at wrong places, the fox terrier had learnt to
go straight and without hesitation to the right spot. In this case
the lifting of the latch was unquestionably hit on by accident, and
the trick was only rendered habitual by repeated association in the
same situation of the chance act and the happy escape. Once firmly
established, however, the behaviour remained constant throughout the
remainder of the dog’s life, some five or six years.
[Illustration: FIG. 21.--Fox-terrier lifting the latch of a gate.]
Mr. E. J. Shellard observed[63] an act of similar import in a Scotch
staghound, which “appeared at first to be the result of thought,”
but which, on closer observation, was clearly seen to be the result
of intelligence in the restricted sense of the term. The dog released
the lever-latch of a yard door. “At first he raised his paws to the
door and scratched violently, manifesting various signs of impatience.
His scratches, which extended from the top of the door downwards, and
over the whole area, would thus inevitably at some time or other reach
the handle of the latch, which was thus struck forcibly downwards, the
latch itself rising upwards. The door would then open from the weight
of the dog pushing against it. The dog always opened the door in this
manner from the time when the incident was first noticed until he left,
a period of about three years. The door was opened with no greater
ease at the expiration of that period than at the commencement. His
paws would strike various parts of the door, and he never appeared to
exercise any degree of judgment in the localization of his strokes, the
fact of his paws striking the handle of the latch being a necessary
result, providing the dog had sufficient patience and strength to
continue.”
One or two more experiments with my fox terrier may be briefly
described. I watched his behaviour when a solid indiarubber ball was
thrown towards a wall standing at right angles to its course. At first
he followed it right up to the wall and then back as it rebounded. So
long as it travelled with such velocity as to be only just ahead of
him he pursued the same course. But when it was thrown more violently,
so as to meet him on the rebound as he ran towards the wall, he
learnt that he was thus able to seize it as it came towards him. And,
profiting by the incidental experience thus gained, he acquired the
habit--though for long with some uncertainty of reaction--of slowing
off when the object of his pursuit reached the wall so as to await its
rebound. Again, when the ball was thrown so as to glance at a wide
angle from a surface, at first--when the velocity was such as to keep
it just ahead of him--he followed its course. But when the velocity
was increased he learnt to take a short cut along the third side of a
triangle, so as to catch the object at some distance from the wall. A
third series of experiments were made where a right angle was formed
by the meeting of two surfaces. One side of the angle, the left, was
dealt with for a day or two. At first the ball was directly followed.
Then a short cut was taken to meet its deflected course. On the fourth
day this method was well established. On the fifth, the ball was thrown
so as to strike the other or right side of the angle, and thus be
deflected in the opposite direction. The dog followed the old course
(the short cut to the left) and was completely non-plussed, searching
that side, then more widely, and not finding the ball for eleven
minutes. On repeating the experiment thrice, similar results were that
day obtained. On the following day the ball was thrown just ahead of
him, so as to strike to the right of the angle, and was followed and
caught. This course was pursued for three days, and he then learnt
to take a short cut to the right. On the next day the ball was sent,
as at first, to the left, and the dog was again non-plussed. I did
not succeed in getting him to associate a given difference of initial
direction with a resultant difference of deflection.
I may here mention that, whenever searching for a ball of which he had
lost sight in the road, he would run along the gutter first on one
side and then on the other. A friend who was walking with me one day
regarded this as a clear case of rational inference. “The dog knows,”
he said, “the effects of the convex curvature of the road as well as we
do.” I am convinced, however (having watched his ways from a puppy),
that this method of search was gradually established on a basis of
practical experience. No logical inference on his part is necessary for
the interpretation of the facts; and we should not assume its presence
unless the evidence compels us to do so.
Dr. E. L. Thorndike, in a monograph on “Animal Intelligence” published
as a supplement to the _Psychological Review_ (June, 1898), has fully
described and carefully discussed a number of interesting experiments.
The subjects (one might, alas! almost say victims) of some of these
were thirteen kittens or cats from three to eighteen months old. His
method of investigation shall be stated in his own words.
“After considerable preliminary observation of animals’ behaviour
under various conditions, I chose for my general method one which,
simple as it is, possesses several other marked advantages besides
those which accompany experiment of any sort. It was merely to put
animals when hungry in enclosures from which they could escape by
some simple act, such as pulling at a loop of cord, pressing a lever,
or stepping on a platform. The animal was put in the enclosure,
food was left outside in sight, and his actions observed. Besides
recording his general behaviour, special notice was taken of how he
succeeded in doing the necessary act (in case he did succeed), and a
record was kept of the time that he was in the box before performing
the successful pull, or clawing, or bite. This was repeated until the
animal had formed a perfect association between the sense-impression
of the interior of that box and the impulse leading to the successful
movement. When the association was thus perfect, the time taken to
escape was, of course, practically constant and very short.