Since hearing is an important sense in pigeons, we should expect them to be capable of useful acoustical associations. Several things occurred in the course of the two preceding experiments which seemed to indicate that this is true; for example, although I could move about, rather noisily, in the darkened room, without apparently disturbing any of the birds, some few showed signs of fright (moving about restlessly) on hearing the low, grating noises made by lifting the hanging door of the cage, sounds which had always preceded the handling of the subjects before experimentation, and which had probably become signs to them of being taken.
FIG. 4. Learning-curves: A, in Labyrinth L; B, in Labyrinth M. Divisions of ordinates indicate minutes; of abscissas, successive daily trials. The rise on curve A for tests 23 and 26 was due to diminution of illumination of room.
To investigate this kind of association I constructed a labyrinth (see Fig. 5) in connection with which sounds could be utilized as one form of sense-data. The passages were so arranged that along the route leading to the food there were three blind alleys, which the animals would surely enter before mastering the course. In another part of the room were placed, very close to each other, two electric gongs of the same size, but of different material. One was of metal and gave a clear ringing sound; the other was of wood and gave a low rattling noise.
When an animal was learning the route (as in the other two mazes) I sounded the gongs, the metallic, as the bird approached and entered the blind alleys, by openings M, O, and R, and the wooden, as it emerged from them and proceeded along the proper course, and occasionally after it had reached the food. The ringing sound was also given after the animal passed P and was approaching Q. When the new route was fairly well learned, I changed the order of the sound stimuli, ringing one gong at the places where the other had previously been sounded, and compared the records thus obtained with those obtained when the sounds were given in the original order. As an animal is liable to become confused by the sounds, or else quickly accustomed to them, I thought it best to give only a few trials, one trial with the usual order of sound stimulations, the next immediately following with the reversed order, and so on till four pairs of records had been secured, the series of trials being completed in a single day. Four animals were thus tested. The periods of the various trials are shown in Table III.
TABLE III. SOUND ASSOCIATION, LABYRINTH H
Time required to reach food under different sound conditions
| I | II | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Order of gongs the same as when course was being learned. | Order of gongs reversed. | ||||||||||
| Animals | Animals | ||||||||||
| Trials | A | B | E | G | Trials | A | B | E | G | ||
| ˝ | ˝ | ˝ | ˝ | ˝ | ˝ | ˝ | ˝ | ||||
| (1) | 13 | 19 | 24 | 17 | (1) | 14 | 16 | 18 | 27 | ||
| (2) | 16 | 12 | 13 | 16 | (2) | 37 | 17 | 16 | 27 | ||
| (3) | 10 | 16 | 20 | 14 | (3) | 14 | 19 | 26 | 11 | ||
| (4) | 12 | 19 | 10 | 12 | (4) | 27 | 22 | 21 | 14 | ||
| Total, | 51 | 66 | 67 | 59 | ˝ | Total, | 92 | 74 | 81 | 79 | ˝ |
| 243 | 326 | ||||||||||