ABSTRACT
A code can be thought of as an internal representation of an external stimulus. According to D. H. Lawrence, a representation is a response, either overt or covert, that intervenes between the external stimulus and the overt response required by the task. W. W. Cumming, R. Berryman, and L. R. Cohen and later D. E. Carter and T. J. Werner expanded the notion of coding to include stimuli that had not been experienced. Cumming, Berryman, and Cohen trained pigeons on a matching-to-sample task in which pigeons learned to respond to the red, green, or blue comparison stimulus that matched the sample on each trial. Gumming and Berryman argued that the pigeons' response to the novel yellow sample was the coding response that they had learned to make in the presence of the red sample.
