[Illustration: FIG. 14.] The curves on page 60 are to be interpreted in the same way as those for the cats, and are on the same scale. The order in which No. 1 took up the various associations was AA, BB, BB1, G, N, CC, II, O. The percentage of dogs succeeding in the various boxes is given below, but is of no consequence, because so few were tried, and because the motive, hunger, was not perhaps strong enough, or equal in all cases. In AA 3 out of 3. In BB 0 out of 2 (that is, without previous experience of AA). In CC 1 out of 2. In II 3 out of 3. In M 1 out of 2. In N 1 out of 3. In G 1 out of 3. EXPERIMENTS WITH CHICKS The apparatus was as follows: [Illustration: FIG. 15. FIG. 16. FIG. 17.] P was simply a small pen arranged with two exits, one leading to the inclosure where were the other chicks and food, one leading to another pen with no exit. The drawing (Fig. 15 on this page) explains itself. A chick was placed at A and left to find its way out. The walls were made of books stuck up on end. Q was a similar pen arranged so that the real exit was harder to find. (See Fig. 16.) R was still another pen similarly constructed, with four possible avenues to be taken. (See Fig. 17.) S was a pen with walls 11 inches high. On the right side an inclined plane of wire screening led from the floor of the pen to the top of its front wall. Thence the chick could jump down to where its fellows and the food and drink were. S was 17 × 14 in size. T was a pen of the same size as S, with a block of wood 3 inches by 3 and 2 inches high in the right back corner. From this an inclined plane led to the top of the front wall (on the right side of the box). But a partition was placed along the left edge of this plane, so that a chick could reach it only _via_ the wooden block, not by a direct jump. U was a pen 16 × 14 × 10 inches. Along the back toward the right corner were placed a series of steps 1½ inches wide, the first 1, the second 2, and the third 3 inches high. In the corner was a platform 4 × 4, and 4 high, from which access to the top of the front wall of the pen could be gained by scrambling up inside a stovepipe 11 inches long, inclined upward at an angle of about 30°. From the edge of the wall the chick could, of course, jump down to food and society. The top of the pen was covered so that the chick could not from the platform jump onto the edge of the stovepipe or the top of the pen wall. The only means of exit was to go up the steps to the platform, up through the stovepipe to the front wall, and then jump down.