Book reviews

Balsam, P. D. and Tomie, A. (Eds.) Context and learning. Hillsdale, N.J.: Lawrence Erlbaum Associates. 1985. Pp. xi+ 419. ISBN 0-89859-442-1. £39.95.

Greenberg, G. and Tobach, E. (Eds.). Behavioral evolution and integrative levels: The T. C. Schneirla Conference Series. Hillsdale, N. J., Lawrence Erlbaum Associates. 1984. Pp. 307. ISBN 0-89859-363-8. $34.50. £28.75.

Commons, M. L. and Nevin, J. A. (Eds.). Quantitative analyses of behavior. Vol. 1: Discriminative properties of reinforcement schedules. Cambridge, Mass.: Ballinger. 1981. Pp. xxvii + 437. ISBN 0-88410-377-3 (v.1). Hardback. $42.50.

Lynch, G., McGaugh, J. L. and Weinberger, N. M. (Eds.). The neurobiology of learning and memory. New York: The Guilford Press. 1984. Pp. 528. ISBN 0-89862-645-5. £65.00.

Toates, F. M. Motivational systems. Cambridge: Cambridge University Press. 1986. ISBN 0-521-26854-0 (Hardback) £22.50; ISBN 0-521-31894-7 (Paperback) £7.95.     

Tests for inhibition after extinction of a conditioned stimulus in the flavour aversion procedure

In four experiments, rats received flavour aversion conditioning followed by extinction. The flavour was then subjected to retardation and summation tests. Experiment 1 showed that reacquisition of an extinguished flavour aversion was retarded with respect to the performance shown by rats for whom the flavour was novel. No retardation was found, however, with respect to a control group that had been given non-reinforced pre-exposure to the flavour. Experiment 2 demonstrated that extinction showed the same sensitivity to the effects of a retention interval as did latent inhibition, consistent with the view that the retardation effect was a consequence of the occurrence of latent inhibition during extinction. An extinguished stimulus was also found to alleviate the response governed by aseparately trained excitor in a summation test (Experiments 3 and 4), but the size of this effect did not exceed that produced by a control stimulus when the procedure used ensured an equivalent aversion to the test excitor in the two cases. These results challenge the proposal that extinction can turn a stimulus into a net inhibitor.     

Discrimination between outcomes in instrumental learning: Effects of preexposure to the reinforcers

In two experiments rats received instrumental training with two response levers, one response being reinforced by sucrose solution and the other by sucrose pellets. Prior to a test session, on which both levers were made available in the absence of reinforcement, the rats were given free access to one of the reinforcers, a procedure known to reduce its value. It was found that the rats responded at a lower rate on the lever that had produced the now-devalued reinforcer, but that this effect was substantial only in rats that had received preexposure to the two reinforcers before instrumental training was begun (Experiment 1). Experiment 2 demonstrated that this effect was obtained only when presentations of the two reinforcers were presented according to an inter-mixed schedule during preexposure. It is suggested that this result constitutes an instance of the perceptual learning effect in which intermixed preexposure to similar events enhances their discriminability.