"Perception" versus "Learning": The effect of different instructions upon the central tendency shift

Abstract.— Earlier studies of context effects in stimulus generalization, especially in the adaption-level tradition, have failed to take into account the subjective difference between a learning experiment and an experiment in perception. In the present study, 68 student subjects were trained to discriminate a 30 cm vertical line from shorter and longer lines, and were subsequently tested for generalization with asymmetrical test series (centering around 34 cm). Half of the subjects were told that they were participating in a perception experiment, the other half that they were participating in a learning experiment. Subjects in the latter condition were considerably more influenced by context and gave a greater number of equivalence responses than did the subjects in the perception condition. Amount of training and discriminability of training stimuli did also influence the central tendency shift, but to a lesser extent.