W. Robert Batsell

“You Will Eat All of That!”: A retrospective analysis of forced consumption episodes ☆

The present research was initiated to examine the prevalence of forced consumption and its role in subsequent food rejection. A forced consumption episode was defined as a situation where Person(s) A forced or demanded Person B to consume a specific substance against Person Bs will. An initial survey of 407 college students revealed that over 69% of them had experienced at least one forced consumption episode. One hundred forty individuals completed a follow-up questionnaire exploring various characteristics of their most memorable forced consumption scenario. Specifically, the most common type of forced consumption (76%) involved an authority figure (e.g. parent, teacher) forcing a child to consume a novel, disliked, or aversive food. In this authority figure scenario, respondents recalled the episode as involving interpersonal conflict and negative affect, and identified the most aversive aspects of this scenario as lack of control and feelings of helplessness. Furthermore, most respondents (72%) reported that they would not willingly eat the target food today. In sum, the forced consumption episode appears to be a unique situation in which distasteful food combines with interpersonal conflict to result in long-lasting food rejection.

One bottle too many? Method of testing determines the detection of overshadowing and retention of taste aversions

A two-bottle testing method generally is regarded as a more sensitive measure of taste aversions than a one-bottle test. The current research compared the sensitivity of one-bottle and two-bottle tests in the detection of taste aversions. Specifically, the experiments were designed to detect both overshadowing (single- vs. compound-element conditioning) and retention interval (5 days vs. 1 day) effects. The groups tested with the one-bottle method evidenced both significant overshadowing and stronger aversions at 5-day retention intervals. On the other hand, the differences on these measures were not significant with the two-bottle tests. It is suggested that the efficacy of the two-bottle test be re-evaluated since it may obscure between-group differences in aversion strength.

Variations in the retention of taste aversions: Evidence for retrieval competition

In six experiments, we examined taste and compound taste/taste aversions at different retention intervals. In Experiment 1, saccharin aversions were significantly weaker 1 day after conditioning than 21 days after conditioning. This effect was determined not to be caused by the aftereffects of illness or differential hydration. With the use of a saccharin/denatonium compound, Experiment 2 demonstrated overshadowing of a denatonium aversion at 21- and 1-day retention intervals, Experiment 4 showed a potentiated saccharin aversion only at the 21-day retention interval, and both Experiments 2 and 4 revealed that the aversion of the taste-only controls was stronger at the later retention interval. Experiments 3 and 5 demonstrated that the differences at the two retention intervals were not caused by unconditioned changes in taste preference. Finally, Experiment 6 showed that extinction of the conditioning environment prior to testing results in stronger saccharin aversions than occur in nonextinguished controls. Collectively, these experiments suggest that testing within a 24-h period after conditioning will result in significantly weaker taste aversions. Also, these results support a retrieval-competition explanation that may account for the weakened aversions at the 1-day testing interval of both groups conditioned to single elements and those conditioned to compounds.

Augmentation, not blocking, in an A+/AX+ flavor-conditioning procedure

An A+/AX+ Pavlovian conditioning design typically produces weakened or blocked conditioning to stimulus X. Two experiments were conducted in which rats first received an odor (A+) paired with an emetic US, and then received odor and taste (AX+) paired with the US. In both experiments, the preconditioned odorfacilitated conditioning to the taste. In Experiment 1, a group that received two odor-illness pairings in A+ conditioning had a stronger taste aversion than a group that only had a single odor-illness pairing. Experiment 2 demonstrated that the strengthened taste aversion in the A+/AX+ condition was not due to stimulus generalization. The results represent a unique outcome in the flavor-aversion literature that is similar to potentiation. We propose that this facilitated conditioning to X in the A+/AX+ design be termedaugmentation.

Taste + odor interactions in compound aversion conditioning.

In three experiments with rats, taste + odor interactions in compound aversion conditioning were investigated. In Experiment 1, two odors (0.02% almond and 0.02% orange) were compared on singleelement odor aversions, taste (denatonium) potentiated odor aversions, and potentiated odor aversions following taste extinction. Although no odor differences were seen following single-element conditioning, both types of potentiated orange odor aversions were stronger than their almond odor counterparts. These data show that odors of similar conditionability are differentially potentiated by the same taste. To determine whether these differences were due to unique perceptual representations, the effects of elemental extinction or compound extinction on aversions to the compound were investigated in Experiments 2 and 3. In Experiment 2, orange odor extinction weakened responding to the compound significantly more than taste extinction did. In contrast, almond odor extinction and taste extinction produced similar decrements in responding to the compound in Experiment 3. These results suggest that the perceptual representation of these specific taste + odor compounds are different, and they are discussed in regard to configural and within-compound association accounts of potentiation.

The role of US novelty in retention interval effects in single-element taste-aversion learning

Retention interval effects are seen in taste-aversion learning when single-element aversions are significantly weaker 24 h after conditioning compared with tests at later intervals. This report contains three experiments which suggest that the source of the increased drinking at the 1-day interval is nonassociative interference produced by the novel conditioning episode. In Experiment 1, a parametric analysis demonstrated that aversion strength increased monotonically over a 30-h period following conditioning, and that by 48 h after conditioning it was stabilized. In Experiment 2, a single US preexposure was used to reduce the novelty of the US prior to conditioning. As a result, animals preexposed to the US had stronger taste aversions than did non-preexposed controls at a 1-day retention interval; however, no differences were seen at a 5-day interval. Experiment 3 investigated whether the counterintuitive outcome of Experiment 2 was due to the summation of environment-illness and taste-illness associations at the 1-day test. The results ruled out the summation argument; the US preexposure did not need to be presented in the conditioning context to strengthen the aversion at the 1-day interval. Collectively, these results suggest that the presentation of a surprising US can interfere with the retrieval of the taste-illness association for a short period after conditioning, and that this contributes to the retention interval effect.

Beyond Potentiation: Synergistic Conditioning in Flavor-Aversion Learning.

Taste-aversion learning has been a popular paradigm for examining associative processes because it often produces outcomes that are different from those observed in other classical conditioning paradigms. One such outcome is taste-mediated odor potentiation in which aversion conditioning with a weak odor and a strong taste results in increased or synergistic conditioning to the odor. Because this strengthened odor aversion was not anticipated by formal models of learning, investigation of taste-mediated odor potentiation was a hot topic in the 1980s. The present manuscript reviews the history of potentiation research with particular focus given to the stimuli that produce potentiation, the conditions that produce potentiation, the possible mechanism of this phenomenon, and possible reasons for the decline of research in this area. Although the number of published reports of potentiation has decreased since the 1980s, recent physiological and behavioral assessments have advanced the field considerably, and the opportunities for future research are bountiful. Recent physiological experiments, for example, have identified the basolateral nucleus of the amygdala as the key brain region to produce taste-mediated odor potentiation (e.g., Hatfield andGallagher, 1995). Also, recent behavioral experiments have extended the generality of synergistic conditioning effects. Studies have shown that odor can potentiate responding to taste (Slotnick, Westbrook and Darling, 1997) and that augmented responding can be produced in the A+/AX+blocking design (e.g., Batsell and Batson, 1999). With the current understanding of where synergistic conditioning may occur in the brain and the new tools to explore synergistic conditioning, we propose various directions for future research to determine whether taste-aversion learning and synergistic conditioning require unique explanations.

Investigation of replacement fluids and retention-interval effects in taste-aversion learning

In two experiments, taste aversions were tested at different retention intervals. Experiment 1 demonstrated that saccharin aversions were significantly weaker when tested 1 day following conditioning than when tested 3, 5, or 10 days after conditioning. It was hypothesized that the increased drinking observed at the 1-day testing interval might be attributable to limited fluid exposure during the conditioning-to-testing interval (CTI). The results of Experiment 2 indicated that providing replacement fluids during the CTI did not eliminate these retention-interval differences. Instead, these results suggested that an alternative associative or nonassociative mechanism was responsible for the retention-interval effect.

Effects of postconditioning inflation on odor + taste compound conditioning

The within-compound association approach has been proposed as an account of synergistic conditioning in flavor aversion learning. One prediction from the within-compound association approach is that following taste + odor compound conditioning, postconditioning inflation of one element of the compound should increase responding to the second element. In four experiments with rats, the AX+/A+ design was used to determine whether postconditioning inflation of A would increase responding to X. In Experiments 1 and 3, responding to X was significantly stronger after AX+/A+ conditioning, as compared with AX+ conditioning. In Experiments 2 and 4, the specificity of the inflation effect was demonstrated, because AX+/A+ conditioning produced a stronger aversion to X than did AX+/B+ conditioning. Furthermore, it appears that the taste + odor association is symmetrical because inflation of the taste aversion increased responding to the odor (Experiments 1 and 2) and inflation of the odor aversion increased responding to the taste (Experiments 3 and 4).

Unconditioned stimulus intensity and retention interval effects.

In single-element taste-aversion learning, retention interval effects are seen if taste aversions are paradoxically weak when they are tested 1 day after conditioning than when they are tested 3 or more days after conditioning. One explanation of this phenomenon is that weaker taste aversions may increase in strength across a retention interval. To test this possibility, rats were given saccharin followed by an unconditioned stimulus (US) of weak, medium, or high intensity; testing occurred after a 1-day or a 5-day retention interval. The results showed retention-interval effects only at medium and high dosage levels, but not following a weak-intensity US. Furthermore, at the 5-day retention interval, aversion strength increased as the intensity of the US increased. However, at the 1-day retention interval, there were no significant differences due to US intensity. In accordance with previous experiments, this outcome suggests that nonassociative factors, such as US novelty, and not associative factors (e.g., US intensity), modulate taste aversion performance on a 1-day test.