| Abstract: | In Exp. I, shallow U-shaped gradients of inhibition in the line-orientation dimension were obtained from birds that had a vertical (0°) line on a green surround correlated with extinction and a blank green surround correlated with reinforcement. Birds that had massed extinction in the presence of the 0° line showed flat gradients. Thus, discrimination training, but not massed extinction, appears to generate inhibitory control. In Exp. II, as in studies of control by a stimulus correlated with punishment, non-differential training across the line-orientation dimension preceded further sessions. Steep inverted gradients about the 0° line were obtained after discrimination training with the 0° line correlated with extinction. Gradients obtained after massed extinction tended to be flat. Again, discrimination training was critical in obtaining negative gradients of stimulus control. |
