Pagina-afbeeldingen
PDF
ePub

If one may say so, the organism plays its hereditary hi cards. This point of view is justified, we think, by the familiar cases where animals in the course of their lifetime, and sometimes in the course of brief experiments, are able to improve upon their hereditary equipment by f establishing novel reflexes on the basis of profitable associations. We may compare with these instances the phenomenon of 'facilitation' in higher animals, in which even a purely automatic and unconscious response to stimulation becomes more and more sensitive and certain ad in its action with repeated use.

m

F

LOW

pe

Bith

Some of the simplest reflexes are very instructive in this connexion. In sea-anemones there is no central nervous system, nothing more than a network of nervecells. Sensory neurons on a tentacle are stimulated by the touch of a fragment of flesh; the nerve impulse passes to a deeper motor neuron and thence to the muscle, the result being that the tentacle curves round the food and bends in towards the mouth. In many cases it passes on the booty to another tentacle, which continues the transport. This is a very simple reflex action, and it suffices for a considerable part of the sea-anemone's everyday life. But deeper scrutiny shows that the behaviour of sea-anemones is not so simple as it appears at first sight. Unpalatable fragments are often refused; sometimes they are positively rejected. In some cases when the sea-anemone is fed with crab's flesh and filter-paper in rapid succession, it soon comes to reject the unprofitable. In two to five days a par ticular tentacle, as Fleure and Walton showed, will refuse to grip the filter-paper. Yet unexperienced adjacent tentacles fell into the trap, though only once or twice. The profiting by experience was somehow transferred by the network of nerve-cells to neighbouring tentacles. Perhaps there is here a glimmering of aware ness, feeble because the nervous system is so diffuse. Prof. G. H. Parker cheated the tentacles of one side of an anemone till they would not be cheated any more, but he found that those on the other side were quite liable to be deceived by faked food. Our view is that most sea-anemones get along very well without 'mind,' in virtue of their inborn and acquired neuro-muscular linkages, and yet sometimes there is in the background

[ocr errors][ocr errors][merged small][ocr errors][merged small][merged small][ocr errors]

hint of an inner awareness that enables the animal to 18e its reflexes in a somewhat new and more unified way. Thus the beautiful Anthea allows a spider-crab to shelter between its base and the rock, and stretches down one of its long tentacles to grip the booty that the crustacean has lugged home to its retreat. It is too soon to offer an argument, but it appears to us very difficult to account for the details of the much-studied commensalism or mutually beneficial partnership between sea-anemones and hermit-crabs without crediting both parties with the stirrings of mind.

From reflexes the inclined plane continues to still simpler reactions, a term which might be conveniently appropriate for responses on the part of animals like sponges, which have no nerve-cells at all, and yet are occasionally able to shut their exhalant orifices in the face of intruders. Similarly the unicellular Protozoa show various effective reactions, though without any nervous differentiation. In some cases there is an interesting testing of one reaction after another in the small repertory - the simplest form of trial and error behaviour.

[ocr errors]
[ocr errors]

We must now return to the other main line in the evolution of animal behaviour, where the characteristic is not enregistration but experiment, not instinctive endowment but plastic educability; not a repertory of ready-made capacities but initiatives and tentatives. This has its finest expression in the intelligent behaviour with which we started, but it is represented at lower levels by experiential learning,' by the establishment of associations (sometimes under parental guidance); by non-intelligent experiments; by a 'trial and error' testing of reactions, and by such simple tentatives as many of the Protozoa illustrate. The simplest behaviour on this line is what we see when a minute infusorian explores the tangle in the field of our microscope. It works its way vigorously among the alga threads, almost like a dog through brushwood. No doubt it is in part reacting, as the dog does, to the diverse stimuli of its environment, but it is at the same time obeying the fundamental urge of hunger and self-assertiveness. If it were the size of a shark, and we were in its vicinity, would we doubt its purposiveness ?

[ocr errors]

wer

te

Paso

erg 3.

That

Vin

atti

Bod

Among larger animals the simple forms of initiative or tentative behaviour are well illustrated by Echino- 1 derms, where the almost universal absence of ganglis forbids us thinking of anything like perceptual inference. ink Of this non-intelligent experimentation a good instance to fin may be found in the behaviour of the common starfish, Asterias rubens, of the seashore. Prouho has observed 2 that some individuals attack small sea-urchins, bristling with spines and equipped with hundreds of minute snapping-blades (pedicellaria), some of them poisonous. The starfish lays one of its arms on the sea-urchin, which responds by reflexly clinching scores of its snapping. spines on the soft suctorial tube-feet of the aggressor. Whereupon the starfish draws away its arm, wrenching off the clinched pedicellariæ, which are unable to let go. It then repeats the performance with another arm, and then with another. When the sea-urchin is thus more or less disarmed, the starfish begins to protrude on it its very elastic stomach, which has poisonous as well as solvent juices, and thus, though a 'soft-mouthed' animal, it soon makes an end of the hard urchin. This is a particularly instructive case, for only some individuals among the starfishes tackle sea-urchins; moreover, what is attempted has to be persisted in until it is finished, if it is to be of any use. There is a spice of originality in the behaviour, which cannot be described as following the line of least resistance. Now, the starfish has no nerve-centres or ganglia, only a superficial nerve-strand up each arm, a ring around the mouth connecting these strands and in some measure unifying their activities, besides a network of nerve-cells in various parts of the body. Since there is no concentration into ganglia, we cannot describe the behaviour by any more psychological word than experimental.

en

Bod

the

ne

her

Our general view, then, is that of two main trendson the one hand, experimenting, initiatives, tentatives; on the other hand, answering back from an inborn or acquired repertory of reaction-capacities. Both modes of behaviour have their advantages and disadvan tages; the perfecting of the second often makes an advance of the first more feasible, yet the very perfection of the instinctive may remove the intelligence.

spur

to

s di

ed t

CONCLUSIONS.

1. By 'mind in animals' we mean whatever in them corresponds in any degree to our own inner life of thinking, feeling and purposing; but we must be prepared to find that what is a powerful stream in ourselves is a very slender rill in many an animal.

2. The inner or psychical life cannot be reduced to a lower common denominator of nervous impulses and the like. The psychological cannot be expressed in terms of the physiological. Mental activity cannot be explained in terms of matter and energy. To mention only one reason, we require mental activity to explain matter and energy.

3. No thinker has attained to clearness in regard to what is called, badly perhaps, the relation of 'Body' and 'Mind.' We say 'badly perhaps,' because that way of putting the question commits one to the theory that 'Body' and 'Mind' can be thought of as separate realities or entities. Perhaps they are separable, as many believe, Ebut this should not be assumed at the beginning of the inquiry. Some thinkers believe that the Mind uses the Body as its instrument, as a musician his violin. To others it seems that mental and bodily, psychical and physical, subjective and objective, are two aspects of one activity which we call Life-just like the concave or inner and the convex or outer surfaces of a dome. And there are other theories. But in any case, the certainty is that there are two sides of the behaviour of man and of higher animals, and that neither can be ignored. Sometimes the physiological or bodily side is more prominent, and we say 'psycho-biosis' or mind-Body. At another time the psychological or mental side is more dominant, and we say 'bio-psychosis' or body-Mind.

4. Animals seldom show more cleverness than is demanded of them by the conditions of their life, and if frequently recurring difficulties can be adequately met by some inborn predisposition of the body, as when elvers swim straight up-stream, or by some ready-made or instinctive equipment that does not need any individual apprenticeship or learning, there is not likely to be much evidence of intelligence on these occasions.

5. In many cases it seems likely that the psychological side of the animal's life does not count for very much in

Bot

ide

[ocr errors]
[ocr errors]
[ocr errors]

that

the ordinary behaviour. That is to say, what the creature does may be sufficiently accounted for by what has been racially enregistered in its mind-Body, or, as some would prefer to say, in its BODY. As Spinoza warned us, we should beware of being dogmatic in regard to what the body, as body, may not be able to do. In such cases we jerk must try to avoid two extremes. We must not think of a minute Mind, which might be called a 'menticule' sitting in the organism out of employment, like an artist without a commission, because the body is sufficient unto itself. We must rather think of the creature as running according to an engrained bodily rule, and running so automatically that the mental side of its behaviour is not in any high degree activated.

[ocr errors]
[ocr errors]
[ocr errors]
[ocr errors]

Along with the finely integrated nervous system of higher animals there is a corresponding integration of igt the inner life, helped by memory and perceived purpose; and the result is an adumbration of what in ourselves we call 'self' or personality. In the lower reaches of the animal kingdom, there is probably no such psychical integration, no unified and unifying mind, but only the ever-flowing, though often slender, psychic rill that probably accompanies all life. To ignore this altogether would be the other extreme, that of reducing the animal to an automatic machine. This is to say dogmatically that mind does not count. It should be noted that while the mental aspect may not be needed to guide behaviour by forming images and inferences, it may be an indispensable factor in the unifying of the life. It may be the esprit de corps. Moreover, feeling is a mental activity as truly as inference is.

ec

[ocr errors]

8

ke

that

But

mer

6. In describing animal behaviour we must not be too generous, reading the man into the beast, and making every creature a Brer Rabbit. On the other hand, we must not be too stingy, trying to make out that the animal is no more than an automatic machine, or never more than a big bundle of reflex actions. We must follow what is sometimes called the 'Lloyd Morgan principle—that in describing any particular case we must not assume higher mental qualities than are necessary for a satisfactory description. In so doing we may do the animal an injustice, for we know that in our own case the simplest explanation or description is

ell

End

thi

ch

« VorigeDoorgaan »