Spatial Peak Shift and Generalization in Pigeons

How pigeons generalize across spatial locations was examined in the 4 experiments reported in this article. During training, a square was presented at a fixed height at 1 of 2 horizontal locations on a monitor screen. One location (S +) signaled reward, whereas the other one (S ) signaled no reward. The birds were then tested occasionally with a range of locations. After training with S+ only, the generalization gradient peaked at S + and was approximately Gaussian in shape. After training with equal numbers of S + and S trials, response rates were higher on the S + side of the distribution. This asymmetry diminished over testing. When the S + and S were close together, the peak of responding was shifted on initial generalization tests. Generalization gradients along the orthogonal vertical dimension were approximately exponential in shape. This is the first demonstration of generalization and peak shift in the spatial domain.