Flavor preferences produced by backward pairing with wheel running

In 3 experiments rats given 8 sessions of preexposure to wheel running acquired a preference for a flavor that was given immediately after each of 4 subsequent sessions of wheel running. Such flavor preference was less likely when rats were given the same conditioning procedure but without preexposure to wheels (Experiment 1) or when access to flavor was delayed by 30 min following a wheel session (Experiment 2). When rats were given a flavor before each wheel session, the resulting conditioned aversion was greater in rats that had no prior exposure to wheel running (Experiment 3). These results show that whether an aversion or preference for a flavor is produced by wheel running depends on an interaction between prior wheel experience and the sequence of events.     

Expression of flavor preference depends on type of test and on recent drinking history

The persistence of a conditioned flavor preference was examined in 3 experiments. All contained an initial acquisition phase in which half the rats were given almond odor mixed with sucrose (AS) in some sessions and water (W) only in other sessions, whereas the other half (controls) were given explicitly unpaired exposures to almond (A) and sucrose (S) in separate sessions. Subsequent 2-bottle choice tests revealed a persistent preference for A, despite extinction exposure to A or S, but this depended on the choice offered on test: Exposure to A did not extinguish the preference for A over W but did reduce the preference for AS over S; conversely, exposure to S did not extinguish the preference for AS over S but did reduce the preference for A over W. These results indicate that flavor preferences can be resistant to extinction procedures but suggest that the expression of such preferences in choice tests depends on an adaptation-level process.     

High ambient temperature reduces rate of body-weight loss produced by wheel running

This study examined the effect of ambient temperature (AT) on the relationship between activity and weight loss. Compared with a neutral AT of 21 degrees C, high ATs of 27-29 degrees C produced a slower rate of weight loss in rats given 1.5-hr food access and 22.5-hr running-wheel access in a standard activity-based anorexia (ABA) procedure (Experiments 1 and 2). The high AT did not affect food intake or wheel running in Experiment 1, but did reduce running in Experiment 2. Switching from neutral to high AT had only a transient effect on weight loss when wheel access was maintained (Experiment 2) but resulted in less weight loss when wheel access was prevented (Experiment 3). Giving rats only 3 hr of wheel access each day at a neutral AT also produced substantial weight loss, but less if for the rest of each day they were maintained at a high AT (Experiment 4).     

Weight Loss in Rats Produced by Running: Effects of Prior Experience and Individual Housing

To investigate factors affecting activity-based anorexia (ABA) or activity-stress (AS), rats were given 2-hr access to a running wheel immediately prior to their daily 1.5-hr food access during the light cycle. This produced a reduction in food intake, a steady increase in running, and a large drop in body weight with a prolonged delay before weight recovery began. Experiment 1 found that these effects were reduced in rats with prior experience of eating at this time of day. In contrast, prior experience of running in the wheel when on ad lib food enhanced these effects in Experiment 2, where a subsequent change for half the subjects to individual housing produced a further decrease in body weight. The latter factor was investigated from the outset of Experiment 3 and again individually housed rats showed greater weight loss than did group-housed rats. This experiment also found that in rats of the same age a low initial body weight predicts greater vulnerability to ABA. It was concluded that ABA results from activity-induced reduction of feeding, which prolongs adaptation to a new feeding schedule and is accentuated by social isolation.     

Instrumental learning as a result of omission training on wheel running

The present experiment sought to provide unequivocal evidence of instrumental learning under omission training. Hungry rats received free food reinforcement while spontaneously running in a wheel. For an omission group, running postponed or cancelled reinforcers in the presence of a discriminative stimulus (SD) requiring subjects to reduce responding to earn food. Background food presentations were then yoked to reinforcement delivered in the presence of the discriminative stimulus. For a control group, which received the same stimulus presentations, reinforcement delivery was yoked to the experimental group at all times. The procedure allowed both within- and between-subject comparisons between omission and response-independent schedules. The response-reinforcer delay under the omission contingency was adjusted so as to equate reinforcement frequency in the presence and absence of the SD. As the SD was not correlated differentially with reinforcement and the running response did not involve approach or withdrawal to the site of food delivery, the successful discrimination performance observed in this experiment cannot be accounted for by appeal to implicit classical conditioning. Instead, it is suggested that decreased running in the presence of the discriminative stimulus was based on the animals' veridical representation of the negative contingency between the response and reinforcement.     

Book reviews

Premack, D. Gavagai! or the future history of the animal language controversy. Cambridge, Mass.: The MIT Press. 1986. Pp. 164. ISBN 0-262-16099-4. £12.50.

Gandelman, R. (Ed.). Autobiographies in experimental psychology. Hills dale, N. J.: Lawrence Erlbaum Associates, Inc. 1985. Pp. 179. ISBN 0-89859-544-4. £14.00.

Modgil, S. and Modgil, C. (Eds.). B.F. Skinner: Consensus and controversy Lewes, East Sussex: The Falmer Press. 1987. Pp. xii+383. ISBN 1-85000-026-3. Hardback, £35.00.

Boakes, R. A, Popplewell, D. A. and Burton, M.J. (Eds.) Eating habits: Food, physiology and learned behaviour. Chichester: Wiley. 1987. Pp. xii+ 225. IBSN 0-471-90744-8. £20.00.     

Book reviews

Richards, G. (1987). Human evolution: An introduction for the behavioural sciences. London: Routledge & Kegan Paul. Pp. 374. ISBN 0-7102-0326-8. £40.

Roitblat, H. L. (1987). Introduction to comparative cognition. New York: Freeman. Pp. xiv+377. ISBN 0-7167-17784. Hardback £29.95; paperback £17.95.

Pauly, P. J. (1987). Controlling life: Jacques Loeb and the engineering ideal in biology. New York: Oxford University Press. Pp. 252. ISBN 0-19-50424-1. £22.50.