Animal intelligence: Experimental studies

by Edward L. Thorndike

The experiment with 10 and 110 is noteworthy. Although, as can be seen from the figures, the difference is obvious to one looking at the white part of the figure, it is not so to one looking at the black part. No. 1 failed to improve appreciably in fifty trials, probably because his previous experience had gotten him into the habit of attending to the black lines.

Before arguing from the suddenness of the change from failure to success we have to consider one possibility that I have not mentioned, and in fact for the sake of clearness in presentation have rather concealed. It is that the sudden change in the records, which report only whether the animal did or did not go down, may represent a more gradual change in the animal’s mind, a gradual weakening of the impulse to go down which makes him feel less and less inclined to go down, though still doing so, until this weakening reaches a sort of saturation point and stops the action. There were in their behavior some phenomena which might witness to such a process, but their interpretation is so dependent on the subjective attitude and prepossessions of the observer that I prefer not to draw any conclusions from them. On the other hand, records c, g, n, A and D seem to show that gradual changes can be paralleled by changes in the percentage of failures.

In the statement of conclusions I shall represent what would be the effect on our theory of the matter in both cases, (1) taking the records to be fairly perfect parallels of the process, and (2) taking them to be the records of the summation points of a process not shown with surety in any measurable objective facts. But I shall leave to future workers the task of determining which case is the true one.

If we judge by the objective records themselves, we may still choose between two views. (1) We may say that the monkeys did come to have ideas of the acts of going down to the bottom of the cage and of staying still, and that their learning represented the association of the sense-impressions of the two signals, one with each of these ideas, or possibly their association with two other ideas (of being fed and of not being fed), and through them with the acts. Or (2) we may say that the monkeys had no such ideas, but merely by the common animal sort of association came to react in the profitable way to each signal.

If we take the first view, we must explain the failure of the animals to change suddenly in some of the experiments, must explain why, for instance, No. 1 in g should, after he had responded correctly to the ‘no’ signal for 27 trials out of 30, fail in one trial out of four for a hundred or more trials. If the 27 successes were due to ideas, why was there regression? If the animal came to respond by staying still on seeing the K (card 104), because that sight was associated with the idea of no food or the idea of staying still, why did he, in his memory trial, act sometimes rightly, sometimes wrongly, for eleven trials after his acting rightly twice. If he stayed still because the idea was aroused, why did he not stay still as soon as he had a few trials to remind him of the idea? It is easy, one may say, to see why, with a capacity to select movements and associate them with sense-presentations very quickly, in cases where habit provides only two movements for selection and where the sense-presentation is very clear and simple, an animal should practically at once be confirmed in the one act on an occasion when he does it with the sense-impression in the focus of attention. It is easy, therefore, to explain the sudden change in i, l, m, B, C and E. But our critic may add, “It is very hard to suppose that an animal that learned by connecting the sight of a card with the idea ‘stay still’ or the idea ‘no food,’ should be so long in making the connection as was the case in some of these experiments, should take 10, 20 or 40 trials to change from a high percentage of wrong to a high percentage of right reactions.”

If we take the second view, we have to face the fact that many of the records are nothing like the single one we have for comparison, that of the kitten shown in [Fig. 30], and that the appeal to a capacity to form animal associations very quickly seems like a far-fetched refuge from the other view rather than a natural interpretation. If we take the records to be summation points in a more gradual process, this difficulty is relieved.

If further investigation upheld the first view, we should still not have a demonstration that the monkeys habitually did learn by getting percepts and images associated with sense-impressions, by having free ideas of the acts they performed; we should only have proved that they could under certain circumstances.

The circumstances in these experiments on discrimination were such as to form a most favorable case. The act of going down had been performed in all sorts of different connections and was likely to gain representation in ideational life; the experience ‘bit of banana’ had again been attended to as a part of very many different associations and so would be likely to develop into a definite idea.

These results then do not settle the choice between three theories: (1 a) that they were due to a general capacity for having ideas, (1 b) that they were due to ideas acquired by specially favoring circumstances, (2) that they were due to the common form of association, the association of an impulse to an act with a sense-impression rather roughly felt.

It would be of the utmost interest to duplicate these experiments with dogs, cats and other mammals and compare the records. Moreover, since we shall find (1 a) barred out by other experiments, it will be of great interest to test the monkeys with some other type of act than discrimination to see if, by giving the animal experience of the act and result involved in many different connections, we can get a rate of speed in the formation of a new association comparable to the rates in some of these cases.