Nonrelational processing of a sequential duration discrimination by pigeons

Pigeons were trained on a conditional discrimination involving signal duration. Red and green keylights were presented in succession for different durations. The pigeons were then allowed to choose between the two colors, and responding to the color that had appeared for either the shorter or the longer duration was reinforced. Following acquisition, probe trials were presented in which only one color appeared. Performance on these trials indicated that the pigeons had not learned to process the two duration signals in a relational manner, but instead based responding exclusively on the color with longer duration. Implications for the study of representation in animals are considered.