In the case of thirteen of the sixteen tests given with reversed acoustical conditions (see column II) the periods were longer than the corresponding ones given alternately with them for comparison, and there was an average time-lengthening of 5.2 seconds per trial, or 34.2%. The following is a short description of the animals' reactions to the changed conditions. It corresponds to the time-values expressed in column II of the table.
Bird A: test 1, animal undisturbed; test 2, drew back from S, turned to the left and went toward R, but later returned and passed S without pausing; test 3, paused at O for a short interval, but did not enter the blind alley; test 4, paused at O again, later drew back from S, turned to the left and entered blind alley 3; it soon escaped, and this time passed S without being disturbed, although it paused at T and U.
Bird B: tests 1 and 2, animal apparently undisturbed; test 3, a few slight pauses at openings; test 4, drew back from S, entered blind alley 3, but soon escaped and passed S without hesitation.
Bird E: test 1, undisturbed; tests 2 and 4, paused at openings; test 3, turned back from S, entered blind alley 3, and paused at several places later when passing toward F.
Bird G: test 1, many pauses; test 2, turned from S and entered blind alley 3; test 3, undisturbed; test 4, drew back from S, went toward R, but did not enter the blind alley.
As the animals gave little attention to the wooden gong, but were always sensitive to the metallic one, their observed movements probably must be accounted for chiefly on the basis of certain visual and organic sense-data now with, and now without, the ringing sound. The data governing the start (as already noticed) were probably sufficient for the avoidance of the first blind alley when the gongs were reversed. In case of the other two, however, the birds had come to depend upon acoustical data, and when these were lacking as they approached the openings O and Q, the left turn could not readily be initiated, hence certain hesitations and misdirections of movement frequently occurred. Experience with the blind alley in the first experiment assisted the animals in dealing with the second blind alley here, but mistakes were made. Visual data usually were sufficient to produce the proper turn at Q, but when the ringing sound was given just afterwards, it sometimes occasioned the left turn, thus bringing the animals toward the opening of the blind alley. While the tests given were not such as would indicate how far pigeons can discriminate sounds, they certainly show that these birds are capable of useful sound associations, although visual ones are evidently of greater importance to them.
D. Habits in Labyrinth O
I next made tests in which tactual and electrical sense-data could also be utilized. In one of the passages of a simple labyrinth was placed a board 8 in. square and 3/4 in. thick, over which were stretched copper wires which formed a series of interrupted electrical circuits. By closing a key a bird could be stimulated whenever it stepped upon the wire surface. A second key was connected with a metallic gong. When an animal on its way through the maze first stepped upon the wire surface, electrical and acoustical stimuli were given; later it was allowed to walk across the board without being thus stimulated; afterward acoustical stimuli were given it at various parts of the maze.
