Intradimensional and extradimensional shifts in conditional discrimination.

Two groups of pigeons learned a two key conditional discrimination. Color was the conditional stimulus and form the choice stimulus for subjects in one group. Form was the conditional stimulus and color the choice stimulus in the other group. Half the subjects in each group then underwent an intradimensional shift: The conditional stimulus dimension and choice stimulus dimension were unchanged but the correct and incorrect stimulus compounds were reversed. The remaining subjects underwent an extra-dimensional shift in which the conditional stimulus dimension and choice stimulus dimension were reversed. Subjects which experienced an intradimensional shift learned the new conditional discrimination more quickly. It was concluded that subjects followed rules to solve conditional discriminations but also learned the functions of each stimulus dimension.