It

between the method of intelligence and that of reason. 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," 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,† 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

* American Journal of Psychology, vol. viii., no. 4, pp. 431-493. † "Introduction to Comparative Psychology," p. 255.

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.

Mr. E. J. Shellard observed an act of similar import in a Scotch staghound, which "appeared at first to be the result *"Introduction to Comparative Psychology," p. 290.

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

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