Abstract
Pigeons were trained to respond equally to various orientations of three parallel lines projected on a response key. One group was then punished for responding to the vertical lines, but not punished in a line-absent condition. Two other groups were also punished but had no opportunity to make such a discrimination. Orderly generalization gradients were obtained from the discrimination group during recovery from punishment, with least responding to the vertical lines and higher rates to other orientations. Gradients obtained from the non-discrimination groups were flat. A discrimination of punishment contingencies appears to be necessary for a stimulus correlated with punishment to acquire control over its reductive effects.