ATTENTION IN THE PIGEON: TESTING FOR EXCITATORY AND INHIBITORY CONTROL BY THE WEAK ELEMENTS 1

In two experiments, pigeons were trained on a successive discrimination between a color and either a compound S+ or a compound S— consisting of a form superimposed on a second color. Two stimulus control tests followed discrimination training: an attention test in which the form and colors used in training were presented singly and in combination, and then a resistance‐to‐reinforcement test using the form element of S+ or S— and a novel form. In the attention test, the birds trained with a compound S+ responded most to the S+ compound, less to the S+ color alone, and still less to the S+ form on a dark key. Few responses were made to the negative stimulus, either alone or with the S+ form added. The birds trained with a compound S— pecked most at the S+ color and to a compound of the S+ color with the S— form added. The resistance‐to‐reinforcement test showed that the birds trained with a compound S+ responded more to the S+ form than to a novel form. However, the birds trained with a compound S— did not reliably respond more to a novel form than to the S— form. These findings suggested that the form element of a compound S+ gains some excitatory control, but the form element of a compound S— does not acquire inhibitory control. The possibility existed that low levels of responding to the S+ form on a dark background in the first experiment were due to use of a darkened key to separate S+ and S— periods during discrimination training. However, the essential findings were the same in a second experiment in which darkening of the chamber separated S+ and S— periods.