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cases where the intelligent factor operates by taking advantage of a fortuitous occurrence, and we need not depreciate this too much, since many of man's inventions have been made in a more or less similar way. It is said that the Greek eagle lifts the Greek tortoise in its talons to a great height and then lets it fall on the rocks below, with the result that the extremely strong carapace is broken and the muscles exposed. This is an ingenious way of utilising an almost invulnerable animal, but it may have been discovered quite fortuitously. Eagles often lift booty in their talons without stopping in their wild rush, but they often let their captive fall. This would be very apt to occur with a smooth-backed tortoise, and the intelligence might lie in taking advantage of a useful accident, and one that would be likely to happen over and over again and with different eagles. Similar behaviour has been often observed on the part of herring-gulls which lift crabs, sea-urchins, and clams in their bills and let them fall on the rocks or shingle below, with the result that the hard shells are broken, In some places and on some occasions this may be observed frequently among the gulls, and then it may not be observed again for a long time. This requires further observation; but it suggests repeated re-discovery as the result of a natural accident. Rooks deal in a similar way with freshwater mussels.

At various levels of the animal kingdom, from the Protozoa upwards, one sees the pursuance of a random 'trial and error' method in which the creature, in face of some difficulty, tries its various common movements one after the other, and may thus solve a problem. It is seeking satisfaction or the removal of dissatisfaction, and it goes through its repertory of movements. Here we have to do with endeavour, but not with intelligence. In any case it is far below the level of the deliberately purposeful experiments made by the chimpanzee in trying to retrieve the out-of-reach fruit. Intelligence might be inferred if attention were arrested by the movement that proved effective, and if on subsequent occasions the profitless movements were more or less quickly eliminated. One of the lower monkeys wished to get a peanut out of a narrow-necked bottle, and tried all manner of unintelligent shakings. Among these there

occurred holding the bottle inverted in a vertical We position, which of course attained the desired result. But this individual monkey had not the wit to notice what particular movement solved the problem; nor did its fortuitous success lessen during the period of observation the number of subsequent failures. It is profitable to contrast this case with the way in which an untaught thrush, carefully observed by Miss Frances Pitt, learned to open its first wood-snail. In the course of a week it passed through the stages of indifference, interest, fumbling strokes, more effective thrusts, lifting the shell, and finally hammering it on a stone until it broke. But when it reached the solution which it had deliberately sought, it did not require any further experimenting. It had learned its lesson-along an intelligent line.

The term 'habit' should be restricted to the individual enregistration of a novel sequence of actions, which require to be in some way 'learned.' In the sequence one neuro-muscular action automatically calls up another, and that another, and so on; and it is easier that the links in the chain should follow one another than that anything else should happen. As people often speak of 'habit' and 'habits' with other quite different meanings, it might be useful to use the term 'habituation' for the individually acquired enregistration, as well as for the process by which the enregistering is effected. There are two important points: (a) to distinguish habituation, which requires to be individually 'learned,' from instinctive capacities and reflex actions which form part of the inherited organisation; and (b) to recognise that the habituation may be effected by non-intelligent as well as by intelligent repetitions of the same experience.

Thus it is an entirely individual and also peculiar achievement to master a labyrinth of the Hampton Court pattern, as has been done by many animals, such as monkeys, rats, mice, dogs, cats, pigeons, and tortoises. In the course of a few days a docile rat will scamper through the maze to get its food, and some rats that have learned their lesson well are able to traverse the perplexing paths without a mistake after an interval of several weeks. How the rat masters the labyrinth is uncertain, but it can do so apart from sight and smell. It can hardly be credited with having a plan of the

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labyrinth in its head, or with noticing, as a clever boy
might, that there is a 'secret,' like 'second to the right
and third to the left,' which leads the explorer in or out.
It makes mistakes at first, but it gradually eliminates
these; and the probability is that it has a kinesthetic
sense that enables it to remember the effective routine
of movements. It must be noticed that these maze-
solving creatures do not learn in cold blood, but with
an interest whetted by appetite. The 'homing' of
horses and some other mammals is probably kinesthetic;
and as for cats that are transported to a distance in
a basket, more precise information is required, One
requires to know, for instance, the percentage of failures,
and whether a cat that found its way in a few days
from Ayrshire to Fife could have repeated the journey
the following week. The homing' power of ants and
bees is in the main the outcome of learning the region
and taking advantage of landmarks; the case of homing
pigeons is by itself, since man secures a graduated educa-
tion for the birds; the homing of migrant birds remains
a puzzle. The experiments made with brooding terns,
removed in closed baskets from the Tortugas and taken
on board steamer for hundreds of miles into unknown
waters, whence a variable percentage returned in safety,
seem to prove conclusively that there is a 'sense of
direction' whose nature and location are quite unknown.
All this, however, is but to emphasise the point that
habituation is a very important factor, and that the
'learning' process need not be intelligent. Very clear
evidence of this is afforded by the behaviour of starfishes,
which learn to free themselves more and more rapidly
from staples which bind their arms to the experimenting
table, of course without pain or actual contact.
is a gradual elimination of useless movements, but we
dare not speak of anything like intelligence when we
are dealing with animals that have not a single nerve-
ganglion in their bodies. The nerve-cells are not inte-
grated into centres. Nor, on the other hand, can we
put our learning to ride a push-bicycle or to play a game
like tennis at the simple level illustrated by the starfish,
for although there is the important common feature
of eliminating useless movements, man is continually
demanding and receiving intelligent reasons for learning

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as he does. One of the clearest instances of nonintelligent 'learning' is afforded by some experiments on earthworms which were confined in T-shaped tubes filled with soil, one path leading to a mild electric shock and the other to satisfaction. After 120-180 lessons, about six per day, the earthworms learned to avoid the electric path, making only one mistake or two out of twenty trials. But the lesson was learned not less thoroughly by headless earthworms!

こ On a different line of evolution from intelligent behaviour at its various levels are the diverse forms of instinctive behaviour, reaching its finest expression in ants, bees, and wasps. On its physiological side instinctive behaviour is a chain of reflex actions, the histological elements of which and their arrangement in sequences form part of the hereditary organisation of the animal. But in some cases it seems necessary to assume an active psychical correlate, and there is evidence that the instinctive chain of reflexes is suffused with an awareness that is more than sensitiveness to stimuli, and backed by an endeavour that is more than appetite.

For some spiders it has been shown that they construct their web true to the type of the species the very first time they try. Subsequent webs may be stronger and larger, but the first web has the characteristic architecture. As Rösch has shown, the worker honeybee serves an interesting apprenticeship within the hive, being promoted, so to speak, from task to task, all discharged instinctively, until after about a fortnight she passes into the new world of flowers and sunshine. But there the outstanding fact is that she enters and rifles difficult blossoms, collecting nectar as to the manner born. She fills her honey-sac, makes a bee-line for home, executes a peculiar nectar-dance (as Frisch has shown) on the honeycomb, makes her contribution to the communal wealth, and, after a short rest, flies off again for more. Although there are interesting idiosyncrasies, for it is a common saying among bee-keepers that 'bees never do anything always,' the behaviour is for the most part instinctive routine.

One of the most instructive illustrations of instinct is the behaviour of the Yucca moth which pollinates

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the Yucca flower. Emerging from her cocoon, the female moth meets a mate in the air and flies from the encounter to visit a Yucca flower with ripe stamens. She collects a ball of pollen and carries it prominently beneath her mouth; she flies to another Yucca blossom and deposits some eggs in the seed-box; but on this visit she leaves the mass of pollen on the surface of the ripe stigma. The pollen-tubes grow down into the ovary; the egg-cells in the ovules are fertilised and begin to develop; the possible seeds become real seeds; and some of them form suitable food for the larvæ of the moth when these hatch out from the eggs. It is evident that there would be no seeds at all if it were not for the pollinating visits of the moth; it is evident that the nurture of the larvae is ensured by the development of the seeds; and it should be noted that there are plenty of uninjured seeds left to ensure the propagation of the Yucca plant; but the important point for our present purpose is that an animal emerging into a new world goes through a performance hitherto untried, the success of which depends on a regular sequence of steps. An instinct is an inborn capacity for doing apparently clever things, without any need for 'learning' or apprenticeship, though this is not to be taken as denying that the instinctive performance is sometimes perfected by practice,

Many years ago, Sir Ray Lankester drew a clear distinction between (a) the 'little brain' type, reaching a climax in ants and bees, with a rich repertory of instincts and very little power of educability, and (b) the 'big brain' type, reaching a climax in the highest vertebrates, with relatively few instincts in the strict sense but with remarkable powers of learning or profiting by experience. From a different angle Bergson reached the same general conclusion, that instinctive and intel ligent behaviour are on different lines of evolution, each with its own advantages and disadvantages. But these two great kinds of behaviour do not admit of very close comparison, still less of being pitted against each other.

It is useful to dwell for a little on the contrast be tween instinctive and intelligent behaviour. Instinctive behaviour requires no learning, but intelligent behaviour is based on what the naturally nimble brain learns. The

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