[7] The experiments now to be described were for the most part made in the Psychological Laboratory of Columbia University during the year ’97-’98, but a few of them were made in connection with a general preliminary investigation of animal psychology undertaken at Harvard University in the previous year. [8] No. 7 hit the string in his general struggling, apparently utterly without design. He did not realize that the door was open till, two seconds after it had fallen, he happened to look that way. [9] No. 6, in trying to crawl out at the top of the box, put its paw in above the string. It fell down and thus pulled the string. It did not claw at it, and it was 16 seconds before it noticed that the door was open. In all the other times that it escaped the movement was made in the course of promiscuous scrambling, never in anything like the same way that No. 2 made it. [10] No. 3 did not go out until 12 seconds had elapsed after it had pulled the string. [11] The back of the pen adjoined the elevator shaft, being separated from it by a partition 33 inches high. No. 2 heard the elevator coming up and put his paws up on the top of this partition so as to look over. In so doing he knocked the fastening of the cord at that end and opened the door. He did not turn to come out, and I shut the door again. [12] FF was a box 40 × 21 × 24 inches, the door of which could be opened by putting the paw out between the bars to its right and pulling a loop which hung 16 inches above the floor, 4 inches out from the box and 6 inches to the right of the door. [13] KKK was box K with both bolts removed. All that had to be done was to poke the paw out at one side of the door and press down a little bar of wood. [14] The cats and chick were left in for two minutes at each trial, the dogs for from one to one and a half minutes. [15] One result of the application of experimental method to the study of the intellect of animals was the distinction of learning by the selection of impulses or acts from learning by the selection of ideas. The usual method of learning in the case of animals other than man was shown by the studies reprinted in this volume to be the direct selection, in a certain situation, of a desirable response and its association with that situation, not the indirect selection of such a response by the selection of some _idea_ which then of itself produced the response. The animals did not usually behave as if they _thought of_ getting freedom or food in a certain way and were thereby moved to do so, but as if the stimulus in question made immediate connection with the response itself or an intimately associated impulse.