Histological data: Hollard and Davison (1971)

As Mogenson and Cioé (1977) have assumed that our electrodes aimed at the ectostriatum (Hollard and Davison, 1971) were actually located there, we feel that a presentation of the histological data is necessary. Following termination of further experiments (Hollard, 1974) the pigeons, numbered 93, 95, and 119, were sacrificed and perfused with saline followed by 10% formalin. Sections, 50 microns thick, were cut on a freezing microtome. Prints were made by mounting each unstained section of a microscope slide and placing them in a standard photographic enlarger. The electrode tips of Pigeons 93 and 119 were located in the paleostriatal complex. The sections of Pigeon 95 were damaged and precise localization was not possible. Further work in this laboratory has also found that, using the same coordinates, electrode tips tend to fall in the paleostriatum, rather than in the more dorsal ectostriatum at which they are aimed. The paleostriatal placements tended to sustain self-stimulation, whereas others located in the ectostriatum sustained relatively low or unstable rates.     

THE RELATION OF FOOD QUANTITY TO RUMINATION BEHAVIOR

Preliminary work suggested that the quantity of food ingested by retarded individuals who usually ruminated following meals was related to the frequency and duration of ruminating responses. This possible relation was experimentally examined by systematically varying food quantity from regular portions to satiation levels for three retarded individuals who exhibited high levels of ruminating. A clear functional relation of food quantity to ruminating emerged, with satiation procedures producing rapid and large decreases in the relatively high frequencies and durations of ruminating characteristic of baseline food quantity conditions.     

Choosing schedules of signaled appetitive events over schedules of unsignaled ones

Two experiments were completed allowing albino rats to choose between signaled and unsignaled reward conditions. These experiments examined the effects on preference of (1) response dependent versus response-independent reward and, (2) food pellets versus chocolate milk as the reward. All subjects preferred the signaled condition over the unsignaled condition, whether exposed to response-dependent, or to response-independent delivery of rewards. Preference was controlled most effectively by presenting both the signal itself and the correlated stimulus identifying the signaled condition. The signal presented alone (Extinction 3) controlled preference more effectively than did the stimulus correlated with the signaled condition (Extinction 2). The second experiment showed that the quality of the reinforcer (pellets and chocolate milk) did not affect preference for signaled reward since all subjects preferred the signaled condition at levels comparable to those observed in Experiment 1, with food pellets. These results, along with others, argue against species differences, response-dependency, and reinforcer quality as variables affecting the direction of preference.     

Suppression of ethanol-reinforced lever pressing by delaying food availability.

When food was initially available to rats under a fixed-interval 26-second schedule and each liquid-reinforced lever press delayed food availability 8 seconds, suppression of liquid-reinforced lever pressing and liquid consumption occurred when the liquid presented was 4, 8, 16, 32, and 0% ethanol. Suppression did not occur in yoked-control animals, which received food coincidentally with experimental animals but were not directly exposed to the delay dependency. After exposure to the food schedule, each ethanol solution served as a reinforcer in the absence of food presentation. Delaying food availability for increasingly long periods (8 to 2048 seconds) suppressed ethanol-reinforced lever pressing and consumption relative to baseline levels, with the maximum decrease being below the level maintained in the absence of food. However, degree of suppression did not increase monotonically with delay length. Liquid-reinforced performance of yoked-control animals indicated that suppression did not result from changes in the sequencing of food presentation alone.     

TREATING CHRONIC FOOD REFUSAL IN YOUNG CHILDREN: HOME-BASED PARENT TRAINING

We evaluated the effects of a behavioral parent training program on parent and child feeding-related behaviors in the home. We trained mothers to initiate regular offerings of previously rejected (target) foods and to provide contingent attention (i.e., specific prompts, positive reinforcement) to increase their child's acceptance of nonpreferred foods. For 1 subject, we also directed training at increasing self-eating. Results of a nonconcurrent multiple baseline design across 3 mother-child dyads demonstrated that, with training, all mothers increased offerings of target foods and use of specific prompts, and 2 mothers increased levels of positive attention. In turn, children increased their acceptance of target foods and self-eating, thus demonstrating the functional effects of parent training on in-home mealtimes. Temporary increases in food refusals occurred when treatment was initiated but declined as treatment continued. We discuss the results in terms of the potential benefits and limitations of a home-based treatment model.     

Predictive validity of the theory of planned behaviour: the role of questionnaire format and social desirability

The present study was designed to assess the predictive validity of a theory of planned behaviour extended to include self‐identity, in the context of health‐related food choice. Following criticism of the use of questionnaires in social cognitive research, the impact of questionnaire format (random vs structured) and social desirability on questionnaire responses was assessed. Findings indicated that intention was the principal determinant of food choice; attitude, subjective norm and self‐identity were independently predictive of intention. There was only weak evidence to suggest effects of social desirability or questionnaire format on component relationships. The present study indicates that the impact of questionnaire format and social desirability on models such as the theory of planned behaviour is minimal, and that such models are robust predictors of food choice. Copyright © 1999 John Wiley & Sons, Ltd.     

The role of intermittent food in the induction of attack in pigeons

The present experiments evaluated whether transitions in reinforcer probability are necessary to induce attack in pigeons. In Experiment I, three of six pigeons exposed to response-contingent constant-probability food schedules and a photograph of a conspecific as a target exhibited sustained postreinforcement attack on the target. The postreinforcement pattern of attack developed over the course of the experiment and was accompanied by a reduction in the rate of postreinforcement key pecking and an increase in the postreinforcement pause in key pecking. These effects on key pecking resulted in unprogrammed variations in the probability of reinforcement which may have been responsible for the induction of attack. In Experiment II, the attack-inducing properties of a constant-probability response-independent food schedule were compared to a periodic food schedule matched for overall rate of food delivery and to a no-food condition. In addition to attack, the spatial location of the subjects was monitored during each interfood interval. The periodic and aperiodic food schedules generated very different patterns of spatial location. Postfood attack was induced by both food schedules, although the constant-probability schedule induced attack in fewer birds. The no-food condition was not effective in inducing attack in any birds. These experiments indicate that intermittent food schedules without reductions in reinforcer probability are sufficient to induce attack in some pigeons, although not as effective as schedules with transitions in reinforcer probability.     

On the relative contributions of positive reinforcement and escape extinction in the treatment of food refusal

We compared the effects of positive reinforcement alone, escape extinction alone, and positive reinforcement with escape extinction in the treatment of the food and fluid refusal of 4 children who had been diagnosed with a pediatric feeding disorder. Consumption did not increase when positive reinforcement was implemented alone. By contrast, consumption increased for all participants when escape extinction was implemented, independent of the presence or absence of positive reinforcement. However, the addition of positive reinforcement to escape extinction was associated with beneficial effects (e.g., greater decreases in negative vocalizations and inappropriate behavior) for some participants.     

Assessment of attack and drinking in White King pigeons on response-independent food schedules.

Four White King pigeons in Experiment I were exposed to a fixed-time 90-second food schedule with successive access to water and a conspecific target. Drinking per session was sporadic and minimal, while attack per session occurred during most interfood intervals for all animals. Analysis of the temporal distribution of attack showed that the typical postreinforcement pattern of attack developed over the course of the experiment. In Experiment II, the same animals were exposed to a series of fixed-time schedules ranging from 30 to 360 seconds with successive access to water and target. Time engaged in drinking and the number of interfood intervals with drinking were less than that of attack. Food and no-food baselines, which have been typically used to assess schedules-induced drinking and attack, respectively, were used to evaluate the effect of the schedule on attack and water ingestion. Relative to the no-food baseline, both attack and drinking were enhanced by the schedule in all birds. Relative to the food baseline, drinking was slightly suppressed in three birds and attack was enhanced in all. For all animals, the food baseline resulted in more attack and drinking than the no-food baseline.     

The allure of forbidden food: On the role of attention in self-regulation

The aim of the present studies was to examine the impact of food cues on restrained eaters’ attention for food. Previous research has shown that restrained eaters spontaneously activate hedonic thoughts in response to palatable food cues, and that such food cues also lead them to inhibit their dieting goal. We argue that as a consequence, restrained eaters’ selective attention will automatically be drawn towards hedonically relevant food items. Consistent with our expectations, the results of two studies revealed that restrained eaters, but not unrestrained eaters, displayed an attentional bias for hedonically rated food items when they had been pre-exposed to food cues. However, this attentional bias did not occur when restrained eaters were primed with the concept of dieting, thereby rendering the regulation of eating behavior more successful. These findings are discussed in the context of implicit processes in self-regulation.