Robert A. Boakes

Motivational control after extended instrumental training

Hungry rats were trained to press a lever for food pellets prior to an assessment of the effect of a shift in their motivational state on instrumental performance in extinction. The first study replicated the finding that a reduction in the level of food deprivation has no detectable effect on extinction performance unless the animals receive prior experience with the food pellets in the nondeprived state (Balleine, 1992; Balleine & Dickinson, 1994). When tested in the nondeprived state, only animals that were reexposed to the food pellets in this state between training and testing showed a reduction in the level of pressing during the extinction test relative to animals tested in the deprived state. The magnitude of this reexposure effect depended, however, on the amount of instrumental training. Following more extended instrumental training, extinction performance was unaffected by reexposure to the food pellets in the nondeprived state whether or not the animals were food deprived at the time of testing. A second study demonstrated that the resistance to the reexposure treatment engendered by overtraining was due to the animals’ increased experience of the food pellets in the deprived state during training rather than to the more extensive exposure to the instrumental contingency. In contrast to the results of the first two experiments, however, a reliable reexposure effect was detected after overtraining in a final study, in which the animals were given greater reexposure to the food pellets in the nondeprived state.

The knowing nose: the role of knowledge in wine expertise

Wine expertise refers here to a superior ability to discriminate between, recognize and describe different wines. Previous studies give only limited support to the possibility that such expertise relies on inherently superior sensory abilities. Instead, research suggests that it relies heavily on explicit knowledge about wine. The experiments reported here were designed to increase understanding of some of the cognitive processes involved, using approaches employed to investigate expert performance in other domains. The first two experiments compared recall for wine-related words by experts and novices under both intentional (Experiment 1) and incidental (Experiment 2) conditions. Experts recalled more words than novices, but in the intentional condition, they did so only when the words were grouped so as to form possible descriptions of actual wines (Varietal), but not when meaningless combinations of words (Shuffled) were used. The final two experiments tested the ability of novices to produce descriptions of wines that would enable them later to match their own descriptions to the wines. Five dissimilar white wines were used in Experiment 3 with three groups of subjects. The groups were given either a long list of wine descriptors, short lists of variety-relevant descriptors or no list (Control group). Matching performance was best in the short-list condition where it was well above chance level. However, when five wines of the same variety were used (Experiment 4) novice performance did not differ between the control and short-list conditions. Overall, the results suggest that expert and novice performances differ partly because novices lack the vocabulary and the knowledge of varietal types that experts employ in such tasks.

A mnemonic theory of odor perception.

The psychological basis of odor quality is poorly understood. For pragmatic reason, descriptions of odor quality generally rely on profiling odors in terms of what odorants they bring to mind. It is argued here that this reliance on profiling reflects a basic property of odor perception, namely that odor quality depends on the implicit memories that an odorant elicits. This is supported by evidence indicating that odor quality as well as ones ability to discriminate odors is affected by experience. Developmental studies and cross-cultural research also point to this conclusion. In this article, these findings are reviewed and a model that attempts to account for them is proposed. Finally, the models consistency with both neurophysiological and neuropsychological data is examined.

Resistance to extinction of conditioned odor perceptions: evaluative conditioning is not unique.

A tasteless odor will smell sweeter after being sampled by mouth with sucrose and will smell sourer after being sampled with citric acid. This tasty-smell effect was found in experiments that compared odor-taste and color-taste pairings. Using odors and colors with minimal taste (Experiment 1), the authors found that repeated experience of odor-taste mixtures produced conditioned changes in odor qualities that were unaffected by intermixed color-taste trials (Experiment 2). An extinction procedure, consisting of postconditioning presentations of the odor in water, had no detectable effect on the changed perception of an odor (Experiments 3 and 4). In contrast, this procedure altered judgments about the expected taste of colored solutions. Evaluative conditioning (conditioned changes in liking) is claimed to be resistant to extinction. However, these results suggest that resistance to extinction in odors is related to the way they are encoded rather than to their hedonic properties.

Perceptual and cognitive aspects of wine expertise

This paper reviews experimental studies of wine expertise and the evidence that experts are better than novices at discriminating between, recognising, and describing wines in a consistent manner. An Australian Wine Knowledge test is reported that discriminates well between wine experts and novices (1st-year undergraduates). We examine the issue of whether expert performance is based on superior sensory ability, on fluency in “wine talk”, or on knowledge about wine. Despite some evidence for more effective perceptual encoding in regular wine drinkers, it appears that expert performance may rely heavily on explicit knowledge.

Activity-based anorexia in rats as failure to adapt to a feeding schedule.

Progressive weight loss resulting from restriction to a daily 1.5-hr feeding period and access to a running wheel, the Activity-Based Anorexia (ABA) effect, was obtained in 3 experiments. However, bodyweight recovered when adaptation to the feeding schedule preceded access to the wheel (Experiment 1), when feeding was at the start of the dark period (Experiments 2 and 3), and when wheel access was denied in the 4 hr before food (Experiment 4). It was concluded that ABA results from interference with adaptation to a new feeding schedule due to the development of anticipatory behavior.

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.

Activity-based anorexia: ambient temperature has been a neglected factor.

Activity-based anorexia refers to the self-starvation of rats exposed to experimental conditions that combine restricted access to food with access to an activity wheel. This paper compares previous studies of this phenomenon in relation to the ambient temperatures (AT) that were employed. On this basis, and from some more direct evidence, we argue that AT is an important, but neglected, factor in activity-based anorexia research. More attention to AT is needed in future research, since its neglect threatens the validity of conclusions drawn from those studies. Furthermore, direct examination of the effect of AT on activity-based anorexia will allow a better understanding of the mechanisms underlying this phenomenon and the possible clinical implications for the treatment of human anorexia nervosa.

SIMULTANEOUS ACTIVATION OF THE REPRESENTATIONS OF ABSENT CUES RESULTS IN THE FORMATION OF AN EXCITATORY ASSOCIATION BETWEEN THEM

It is a common assumption of associative theories of learning that no change in the strength of an associative connection between 2 cues is possible in the absence of those cues. However, recently suggested modifications to associative theory (A. Dickinson & J., Burke 1996) have questioned this assumption by arguing that if the representations of 2 cues are simultaneously retrieved from memory, an association will be formed between them even though the cues themselves are not present. A flavor preference procedure was used to find evidence for such associations. In 3 experiments a novel excitatory connection was formed between the representations of peppermint and sucrose in their absence. This suggests that the assumption that cues cannot undergo a change of associative strength in their absence should be abandoned. The tension between the current results and accounts of mediated conditioning is discussed, and some suggestions regarding the difference between the 2 procedures are proposed.

Chronic restricted access to 10% sucrose solution in adolescent and young adult rats impairs spatial memory and alters sensitivity to outcome devaluation

Although increasing consumption of sugar drinks is recognized as a significant public health concern, little is known about (a) the cognitive effects resulting from sucrose consumption; and (b) whether the long-term effects of sucrose consumption are more pronounced for adolescents. This experiment directly compared performance on a task of spatial learning and memory (the Morris Water Maze) and sensitivity to outcome devaluation following 28 days of 2-h/day access to a 10% sucrose solution in adolescent and young-adult Wistar rats. Sucrose groups developed elevated fasting blood glucose levels after the diet intervention, despite drawing <15% of calories from sucrose and gaining no more weight than controls. In subsequent behavioral testing, sucrose groups were impaired on the Morris Water Maze, with some residual deficits in spatial memory observed more than 6 weeks after the end of sucrose exposure. Further, results from outcome devaluation testing indicated that in the older cohort of rats, those fed sucrose showed reduced sensitivity to devaluation of the outcome, suggestive of differences in instrumental learning following sucrose exposure. Data provide strong evidence that sucrose consumption can induce deficits in spatial cognition and reward-oriented behavior at levels that resemble patterns of sugar drink consumption in young people, and which can remain long after exposure.