Generalization across dimensions: A model for three-alternative choice

This experiment was an investigation how reinforcers for one response in the presence of one stimulus may generalize to other dimensionally related stimuli. Four pigeons were trained on a three-alternative concurrent variable-interval schedule in which, after an initial condition, extinction was arranged for one alternative. In Part 1, we varied the reinforcer rate on a dimensionally distant alternative while keeping the reinforcer rate on the dimensionally closer stimulus constant. In Part 2, the reinforcer rate for the distant alternative was kept constant and that for the closer alternative was varied. Increasing the reinforcer rate for the closer alternative increased responding on the extinction alternative, but increasing the reinforcer rate on the distant alternative decreased extinction response rates. This result is predicted by the generalization across dimensions model. This model also helps to explain the results from previously reported choice research that involves multiple alternatives, and particularly why Luce's indifference principle is sometimes supported and sometimes not.