Paleostriatal lesions and instrumental learning in the pigeon

In three experiments, pigeons with lesions of the paleostriatum (experimental subjects) and unoperated control birds were trained on tasks designed to assess their instrumental learning abilities. In Experiment 1, using an orthodox Skinner box, training was given on a variable interval (VI) followed by a fixed interval (FI) schedule of reinforcement and only non-significant differences between the groups emerged. Experiment 2 examined the performance of the same subjects on a VI schedule in which a response-contingent signal accompanied reinforcement. For control subjects the presence of the signal resulted in a low rate of response compared with that found in equivalent conditions with the signal omitted. Experimental subjects showed the same response rate when the signal was present as when it was absent. Experiment 3 employed naive subjects, and a Skinner box modified to facilitate key-pecking in total darkness. In this apparatus, experimental subjects showed a lowered response rate on a VI schedule. These tasks were analyzed in terms of the classical (stimulus-reinforcer) and instrumental (response-reinforcer) learning they involve. The results suggest that pigeons with paleostriatal lesions show a deficit in forming response-reinforcer associations, perhaps because the lesions reduce the salience of response-produced cues.     

Book reviews

DONAHOE, J. W. and WESSELS, M. G. Learning, Language and Memory. New York: Harper & Row. 1980. Pp. 513.

GRIFFIN, D. R. The Question of Animal Awareness: Evolutionary Continuity of Mental Experience. (Revised and enlarged edition.) New York: The Rockefeller University Press. 1981. Pp. xi + 209. $13.95. ISBN 87470 035 3.     

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.     

Book reviews

Bloom, A. H. The Linguistic Shaping of Thought : A Study of the Impact of Language on Thinking in China and the West. Hillsdale, N.J.: Erlbaum. 1981. Pp. 106. £9.95. ISBN 0 89859 089 2.

Fodor, J. A. Representations : Philosophical Essays in the Foundations of Cognitive Science. Brghton: Harvester. 1981. Pp. 343. £22.50. ISBN 0 85527 977 X.

Sanford, A. J. and Garrod, S. C. Understanding Written Language: Explorations in Comprehension Beyond the Sentence. Chichester: John Wiley & Sons. 1981. Pp. xiv + 224. £ 11.30. ISBN 0 471 27842 4.

Springer, S. P. and Deutsch, G. Left Brain, Right Brain. San Francisco: W. H. Freeman & Co. 1981. Pp. 243. £4.95 (paperback). ISBN 0 7167 1270 9.

Crystal, D. Introduction to Language Pathology. London : Edward Arnold. 1980. Pp. 214. ISBN 0 7131 62759. £5.50.

Hulme, C. Reading Retardation and Multi-Sensory Teaching. London : Routledge & Kegan Paul. 1981. £12.50. Pp. 200. ISBN 0 7100 0761 2.

Liben, I,. S., Patterson, A. R. and Newcombe, N. (Eds). Spatial Representation and Behaviour Across the Life Span. New York: Academic Press. 1981. Pp. 404. ISBN 0 12 447980 4. £17.80.

Coltman, D. Jean Piaget: Experiments in Contradiction. Chicago: University of Chicago Press. 1980. Pp. 310. ISBN 0 226 66779 0. £13.20.

Hofer, M. A. The Roots of Human Behavior. San Francisco: Freeman. 1981. Pp. xiii + 331. Paperback £6.70. ISBN 0 7167 1278 4.