[Effects of change-over-delay in the signal-key procedure].

The effects of change-over-delay (COD) in discrimination training using the signal-key procedure were investigated in the pigeon. In Experiment I, generalization gradients along the line-tilt dimension following the signal-key procedure with and without COD 2 s were studied. Regardless of the application of COD, following results were obtained: (1) Relative generalization gradients were similar. (2) No behavioral contrast was observed on the operant-key. (3) Some responding to the signal-key occurred during the VI component of the multiple VI EXT schedule. The responses on the signal-key decreased slightly with COD 2 s. These data suggest that the responses on the signal-key were maintained partly by response-reinforcer contingency. In Experiment II, local contrast in the signal-key procedure was investigated. Response distribution within 30 s period of stimulus presentation revealed that COD produced decreased number of responses to the signal-key after 1.5 s of stimulus onset. These suggest that the stimulus-reinforcer contingency is responsible primarily for the local contrast.