1994 年 12 巻 2 号 p. 99-103
Three pigeons were trained concurrently with both Pavlovian feature-positive and feature-negative discrimination tasks (A-, X→A+, B+, Y→B-), in which one diffuse feature stimulus (X) signaled that one target keylight (A) was followed by the food and another diffuse feature stimulus (Y) signaled that another target keylight (B) was not followed by the food. The birds learned both of these two discriminations and produced many pecks to the target keylight in both kinds of positive trials (X→A+ and B+) and few pecks to the target keylight in both kinds of negative trials (A- and Y→B-). In the test after this training, a temporal gap was inserted between the feature and the target, and its effects on the discriminations were investigated. The performance of the feature-positive discrimination was less susceptible to the effect of the gap than that of the feature-negative discrimination.