Taste-aversion retention: An animal experiment with implications for consummatory-aversion alcoholism treatments

Inquiries into the longevity of illness-induced aversions (TAs) in animals are relevant to consummatory-aversion (CA) treatments of human alcoholism. The range of nausea reactions that accompanied the relapses of some alcoholics who had acquired alcohol aversions during covertsensitization (verbal aversion) alcoholism treatment has implicated CA forgetting as one probable contributor to recidivism. CA forgetting is operationalized as aversion diminution during postconditioning periods in which Ss abstain from contact with the target substance. TAs of varying strengths were induced in groups of Sprague-Dawley rats that received low, medium or high doses of the illness-inducing drug cyclophosphamide following saccharin-solution ingestion. TA retention was assessed following saccharin-free intervals of 2–40 days. Each Ss' retention interval was followed by 30 days of two-bottle preference testing, thereby additionally permitting an assessment of TA extinction following differing degrees of TA forgetting. Low-dose Ss displayed moderate strength TAs that were forgotten within 20 days and that had little resistance to extinction when testing began shortly after conditioning. Medium-dose Ss displayed stronger TAs having greater resistance to both forgetting and extinction. Unlike these low- and medium-dose TAs, high-dose TAs were impervious to aversion degradation as a result of forgetting. This finding is interpreted as supporting the attempted induction of intense nausea during covert-sensitization and chemical aversion (emetic therapy) alcoholism treatment. Other related conditioning procedures that may contribute to effective treatment are also discussed.     

Forgetting, preconditioning CS familiarization and taste aversion learning: An animal experiment with implications for alcoholism treatment

The rapid taste aversion acquisition, which typically occurs in many species when ingestion of a novel flavor precedes gastrointestinal distress, is retarded by preconditioning familiarity with the CS flavor. This CS familiarity effect (CSFE) might contraindicate taste aversion approaches to alcoholism treatment since alcoholics are quite accustomed to the tastes of alcoholic beverages. However, many alcoholics do develop strong nausea—induced alcohol aversions under appropriate conditioning parameters. Additionally, the CSFE is attenuated in rats by repeated conditioning trials including discrimination training. The present animal experiment was conducted to determine if the CSFE could additionally be weakened by process of forgetting, i.e. by preconditioning withdrawal of a familiar flavor analogous to an alcoholic's ‘drying out’ before psychotherapeutic intervention. Using saccharin as the CS flavor and cyclophosphamide as the conditioning agent, Sprague-Dawley derived rats acquired no aversions when conditioning was attempted immediately after flavor familiarization. However, significant and equivalent saccharin aversions were observed when conditioning was delayed for either 20 or 100 days after familiarization. These findings imply that the efficiency and cost effectiveness of taste aversion approaches to alcoholism treatment might be enhanced by a pretreatment period of abstinence from alcohol ingestion.     

Chemical aversion conditioning in the treatment of alcoholism: further comments.

The literature on consummatory aversion (CA) conditioning in rats does provide a well-developed theoretical foundation for chemical aversion conditioning. Nevertheless, differences between rats and humans in CA learning suggest caution in extrapolating from the animal laboratory to the treatment of alcoholic patients. Serious methodological problems with studies of emetic therapy with alcoholics preclude unambiguous evaluation of its effects. Emetic therapy is an intrusive and relatively costly form of treatment which has not been shown to be more effective than alternative, less costly methods. The onus is on proponents of this method to demonstrate its specific advantages over alternative treatments.     

Chemical aversion conditioning as a treatment for alcoholism: A re-analysis

The literature on chemical aversion conditioning is characterized by the lack of controlled clinical research. The existing data derive primarily from methodologically inadequate studies. Although short-term conditioned aversion reactions to alcohol have been demonstrated, the independent efficacy of this technique in clinical treatment remains to be shown. Beyond the failure to demonstrate the value of adding chemical aversion conditioning to more standard treatments for alcoholism, evaluation in terms of broader outcome criteria (e.g. safety, intrusiveness, acceptability, the availability of alternative methods, and cost-effectiveness) indicates that chemical aversion conditioning cannot be recommended as a standard form of treatment for alcoholism.     

Formation of food aversions in cancer patients receiving repeated infusions of chemotherapy

Patients receiving emetogenic chemotherapy for cancer have been found to develop aversions to normal dietary items consumed in close temporal relation to treatment administrations. These aversions are presumed to develop via conditioning processes as demonstrated in experimental studies of food aversion learning. The present study used a prospective, longitudinal design to evaluate the possible role of conditioning in the formation of aversions to normal dietary items in women receiving adjuvant chemotherapy for breast cancer. Patients were monitored for the development of aversions to foods and beverages consumed in the 24 hr periods before and after each of eight consecutive chemotherapy infusions beginning with the initial infusion. Data on the prevalence, course, and prediction of aversions to normal dietary items are reported. These results pointed to similarities and differences between aversions formed to normal dietary items during chemotherapy treatment and aversions formed to taste stimuli during experimental conditioning studies. In addition to their theoretical significance, results also suggest possible strategies for preventing the clinical problem of aversions to normal dietary items in chemotherapy patients.     

The acquisition of taste aversions in humans with eating and drinking disorders

A written questionnaire or interview concerned with acquisition of illness-induced (taste) aversions to foods and drinks was given to three groups of people with eating and drinking disorders. These groups consisted of 101 male and 1 female hospitalized alcoholics, 8 male and 8 female college-student heavy consumers of alcohol and 18 females with anorexia nervosa and/or bulimia. In most respects taste-aversion acquisition in these three groups was similar to taste-aversion acquisition in a general college-student population previously studied by Logue, Ophir and Strauss (1981), and to taste-aversion acquisition in other species. In all three groups the aversions were more likely to be reported as having been formed through forward rather than simultaneous or backward conditioning, and long-delay learning was frequent. The aversions usually formed to the tastes rather than to the appearance or other aspects of the foods and drinks. Extinction appeared more effective in decreasing the aversions than did forgetting. While the illness responsible for the aversions forming was usually attributed to the subsequently aversive food or drink, in at least one third of the cases subjects reported that something else might have caused their illness. Aversions were more likely to have formed to relatively less familiar and less preferred foods and drinks. However, the hospitalized alcoholics reported fewer aversions, less generalization of aversions, and stronger nausea as the cause of the aversions than did Logue et al.'s (1981) subjects. About 15% of these subjects reported taste aversions to alcoholic beverages. The college-student heavy consumers of alcohol reported no generalization of their taste aversions, but in other respects were similar to Logue et al.'s subjects. Thirty-one percent of these subjects reported taste aversions to alcoholic beverages. The anorexic and bulimic subjects were also similar to Logue et al.'s subjects with the exception that they, like the hospitalized alcoholics, reported stronger nausea as the cause of the aversions. These data may help to understand and treat people with eating and drinking disorders     

The acquisition of taste aversions in humans

A written questionnaire or an interview was given to 517 undergraduates concerning their acquisition of illness-induced (taste) aversions to foods and drinks. The subjects reported 415 aversions, with 65% of the subjects reporting at least one aversion. The aversions were more likely to be reported as having been formed through forward rather than simultaneous or backward conditioning, and long-delay learning was frequent. The aversions usually formed to the taste of the foods, rather than the appearance or other aspects of the foods. Extinction appeared more effective in decreasing the aversions than did forgetting. The illness responsible for the aversion's forming was usually attributed to the subsequently aversive food, but for 21% of the reported aversions subjects were sure that something else had caused their illness. Aversions were more likely to have formed to relatively less familiar and less preferred foods. Aversions were also more likely to form between the ages of 13 and 20. Generalization of the aversions to similar foods occurred in 29% of the cases. Approximately one fourth of the aversions were to alcoholic beverages. Finally, instances of aversions forming without food or drink consumption and instances of observational learning were reported. The data were quite similar to laboratory taste aversion data collected using other species and can help in optimizing taste aversion treatments of eating and drinking disorders. Taste aversions among humans are frequent and strong.     

Taste aversions conditioned by the aversiveness of insulin and formalin: role of CS specificity

Experimenters in the past have reported that when insulin is used as the unconditioned stimulus (US), rats will learn an aversion to a sodium chloride but not a sucrose solution, whereas with formalin as the US, they will learn an aversion to a sucrose but not a saline solution. The present experiments failed to confirm these findings. Aversions to sucrose were conditioned with insulin and aversions to sodium chloride were conditioned with formalin. The use of a more concentrated sucrose solution in the present study may have been responsible for the successful sucrose-aversion conditioning with insulin. Although the source of the discrepancy in findings concerning aversion conditioning with formalin remains unclear, experiments ruled out numerous possibilities. These experiments also showed that sodium chloride aversion conditioning with formalin is a highly robust phenomenon that occurs with a variety of conditioned stimulus durations and formalin doses, with distributed and massed training, in male and female rats, and even if saline is not the only novel solution presented during conditioning. Furthermore, the aversion can be detected with both single-stimulus and choice test procedures.     

Characteristics of the relapse situation of alcoholics treated with aversion conditioning

Recently, there has been considerable interest in applying the principles of learning theory and operant conditioning to the problems of alcoholism. One principle which may be of value is stimulus control. The principle of stimulus control would suggest that there should be some degree of similarity between the environmental circumstances in which alcoholics do their drinking and the situation where they take their first, post-treatment, drink. The principle of stimulus control also suggests that alcoholics treated with aversion therapy would tend to relapse under environmental conditions that were in some way different from their usual drinking environments.Whether we are able to observe a difference in drinking environments before and after treatment depends on whether we have selected the appropriate stimulus dimensions. The present author is in agreement with Lunde and Vogler (1970) who suggest that; types of liquor consumed; drinking associates; whether at home alone, with others or at a bar; are some of the important characteristics of an alcoholic's learning history. These stimulus conditions could be further simplified to location, type of beverage and social or non-social drinking.Since it is physically impossible to turn time backwards or to have observers follow patients everywhere they go, we must rely on self-reports of alcoholics about their drinking history. Although many clinicians have reservations about the veracity of alcoholics. Guze et al. (1963) report that 97 per cent of alcoholics in a prison population could be correctly diagnosed from their own self-report. Thus, it appears that at least when interviewed in the context of a research study where no contingencies are placed on their behavior, verbal or otherwise, self-report by alcoholics can indeed be reliable. The present study examined the relapse situation of alcoholics in terms of the location of the first drink episode, the social environment, and type of beverage consumed and compared this situation to the usual (most frequent) drinking situation prior to treatment.     

Drugs employed in the treatment of alcoholism: rat data suggest they are unnecessarily severe

A tacit assumption, which has often been made by practitioners of both chemical aversion therapy (CAT) and deterrent therapy of alcoholism, is that efficacy of a drug depends mainly on how noxious it is. We conducted two experiments which challenge this assumption. These experiments compared five noxious drugs employed in the treatment of alcoholism, with lithium, in regard to their ability to reduce rats' drinking of a familiar, readily consumed, ethanol (10% v/v) solution. In both experiments, the dose of lithium was equivalent, in terms of body weight, to the largest daily recommended human dose: the dose of each of the five, noxious drugs was twice this equivalent. In the first experiment, the CAT drugs emetine, ipecac and succinylcholine were compared with lithium: in the second, the deterrent therapy drugs citrated calcium carbimide and disulfiram were compared. Despite the use of comparatively smaller doses of lithium, none of the noxious drugs administered in either experiment produced stronger ethanol aversions than lithium. This supports the use of lithium in CAT, and suggests that unnecessarily noxious drugs are being used in the treatment of alcoholism.     

Cardiac response as an index of the effect of aversion therapy

Recent research shows that aversion conditioning produces conditioned aversions to target stimuli. Conditioned aversions are manifest in the following posttreatment changes in Ss' responses to target stimuli: increased negative evaluations, decreased contact or consumption, and increased phasic heart-rate responses (HRRs). Research on aversion therapy for additive disorders reveals that HRR is a particularly important index of therapeutic change as it is predictive of latency to relapse to drug use. We speculate that aversion conditioning increases Ss' fear and repugnance of target stimuli, that HRRs accurately reflect such defensive responses and that magnitude of defensive response is positively related to latency to relapse. In addition to defensive responding, we believe that HRRs may reflect coping-response or active-avoidance information processing.     

Human Flavor-Aversion Learning: A Comparison of Traditional Aversions and Cognitive Aversions

Traditional flavor aversions form when an organism consumes a flavor prior to an illness-producing unconditioned stimulus (US). Rozin (1986), however, introduced a second type of taste-aversion learning produced by a disgust-eliciting US. In the present work, Rozin's disgust categorization is extended to include other human situations (negative information, forced consumption) in which taste aversions are mediated by cognitive processes. College students completed a self-report questionnaire that addressed their experiences with taste-aversion learning. The results show that cognitive aversions were stronger and longer-lasting than traditional aversions, they formed to foods of animal origin more than to other substances, and they could be produced without nausea. Finally, individuals who reported having a cognitive aversion had significantly more taste aversions than individuals who reported having a traditional aversion. These results provide additional evidence that taste-aversion learning can occur without the direct mediation of an illness-producing US.     

Flavor-illness aversions: potentiation of odor by taste is disrupted by application of novocaine into amygdala

Taste and odor have different properties in toxiphobic conditioning. When each is used alone, taste becomes aversive when followed by immediate or delayed poison, while odor becomes aversive only if followed by immediate poison. However, if odor and taste are presented as a compound and followed by delayed poison, then odor does become aversive when tested alone. It is as if taste has potentiated the odor signal. Several experiments assessed the role of the amygdala in this potentiation effect by anesthetizing the amygdala with 10% novocaine. Novocaine applied 30 min before presentation (Pre-CS) of an odor-taste compound disrupted the potentiated odor aversion but not the taste aversion. In contrast, novocaine applied 1 min after the compound odor-taste or 1 min prior to LiCl poison did not dissociate odor and taste aversions; both odor and taste aversions were facilitated. Novocaine applied 30 min before an odor alone also disrupted an odor aversion induced by immediate LiCl. But identical treatment did not disrupt odor avoidance conditioned by immediate foot-shock, suggesting that amygdala anesthesia does not simply produce anosmia. Pre-CS novocaine treatment also disrupted flavor neophobia prior to conditioning. The results suggest that novocaine applied to the amygdala disrupts the integration of odor with taste and illness during toxiphobic conditioning.     

Individual differences in imagery and reports of aversions

Recent theoretical models highlighting the role of imagery in trauma and aversion learning focus on the role of images in memory (e.g., Brewin, Dalgleish, & Joseph, 1996) and images as substitute stimuli in aversive conditioning (Dadds, Bovbjerg, Redd, & Cutmore, 1997). An unanswered question is whether individual differences in imagery are associated with different rates of traumatisation and aversion states (fear and avoidance of various stimuli). We examine one aspect of this: does high imagery ability correlate with the frequency with which people report aversions? Three samples of university students were tested on the Betts Questionnaire Upon Mental Imagery, the Tellegen Absorption Scale, and a new measure we designed to sample of range of aversions. As hypothesised, vividness of imagery showed positive correlations with number of aversions reported. This relationship held after controlling for general neuroticism and proneness to disgust. Results for absorption showed no relationship. The results are unable to disentangle causal paths but suggest a focus on individual differences in imagery vividness may be fruitful for understanding individual differences in aversion learning.     

Individual differences in imagery and reports of aversions

Recent theoretical models highlighting the role of imagery in trauma and aversion learning focus on the role of images in memory (e.g., Brewin, Dalgleish, & Joseph, 1996) and images as substitute stimuli in aversive conditioning (Dadds, Bovbjerg, Redd, & Cutmore, 1997). An unanswered question is whether individual differences in imagery are associated with different rates of traumatisation and aversion states (fear and avoidance of various stimuli). We examine one aspect of this: does high imagery ability correlate with the frequency with which people report aversions? Three samples of university students were tested on the Betts Questionnaire Upon Mental Imagery, the Tellegen Absorption Scale, and a new measure we designed to sample of range of aversions. As hypothesised, vividness of imagery showed positive correlations with number of aversions reported. This relationship held after controlling for general neuroticism and proneness to disgust. Results for absorption showed no relationship. The results are unable to disentangle causal paths but suggest a focus on individual differences in imagery vividness may be fruitful for understanding individual differences in aversion learning.     

Relative potency of foods and drinks as targets in aversion conditioning

The potency of food stimuli as targets in aversion learning was examined using an interference paradigm. In the first study, foods interfered with liquid aversions but liquids did not interfere with food aversions. In the second study, food aversions were found to be resistant to interference by other foods. These findings suggest that foods are relatively potent targets in aversion conditioning in that they are resistant to interference by both foods and drinks. The final study examined the contribution of flavor intensity and nutrient density to the potency of aversion conditioning. The relative potency of foods over drinks may reflect differences in their intensity as well as their different roles in toxin avoidance and nutrient selection.     

Human classical aversion conditioning: Nausea versus electric shock in the reduction of target beverage consumption

Two experiments were conducted to investigate the effectiveness of the nausea-pro-ducing Pseudo-Coriolis Effect (PCE) in conditioning aversions to beverage consumption. The first experiment assessed the effectiveness of this procedure while controlling for demand characteristics. The second experiment compared this procedure with electrical aversion conditioning. This study demonstrates the effectiveness and relative superiority of the PCE in classical aversion conditioning. Consideration is given to the parameters and potential applications of this procedure     

Flavour-odour compound conditioning: Odour-potentiation and flavour-attenuation

Five experiments employed a toxiphobia conditioning paradigm to examine the strengths of odour and flavour aversions when conditioned separately and in compound. When conditioned in compound, odour aversions were stronger than when conditioned separately, i.e., the flavour potentiated the odour (Experiment Ia), but flavour aversions were weaker than when conditioned separately, i.e., the odour attenuated the flavour (Experiment Ib). The duration of exposure to the reinforced compound governed the nature of the interaction between the components: at a brief exposure, the flavour overshadowed the odour; at a long exposure, the flavour potentiated the odour (Experiment II). The remaining experiments examined the mechanism subserving the potentiation effect. Experiment III demonstrated that extinction of the flavour associate of the odour attenuated the odour aversion but further conditioning of the flavour did not strengthen the odour aversion. Experiment IV confirmed this effect of extinction but also found a comparable attenuation of the odour aversion from extinction of a separately conditioned flavour. Experiment V examined the previous failure to influence the strength of the odour aversion by strengthening the flavour aversion. In this experiment, conditioning the flavour associate or a separately conditioned flavour with a more potent US augmented the strength of the odour aversion. The results did not provide support for the idea that the potentiation phenomenon reflects the formation of within-compound associations but did indicate that a potentiated odour aversion could be modulated by manipulations designed to alter the US representation.     

The effect of three procedures for eliminating a conditioned taste aversion in the rat

Although extinction procedures have been the most common techniques used to eliminate conditioned taste aversions, several studies have employed postconditioning exposure to the US instead. To date, a comparison of the effectiveness of these two techniques has not been possible, because there were differences in the conditioning phases of these studies. In the present study, after an aversion to saccharin had been established, rats were administered 1, 5, or 10 extinction trials, 1, 5, or 10 postconditioning exposures to the US, or a period of no treatment. Then, all rats received seven two-bottle extinction tests. Five or ten extinction trials reduced the aversion to saccharin most effectively. Five or ten postconditioning presentations of the US were also effective. However, this effect was not noticeable until the fourth of seven test trials, suggesting an elimination procedure-test trials interaction. Neither the extinction nor the US postexposure procedure completely eliminated the aversion. In addition: (i) a single postconditioning exposure to either the CS or the US was ineffective in attenuating the aversion; and (ii) when no postconditioning treatment was administered, the strength of the aversion was undiminished for 20 days.     

Is blockade of conditioned flavor aversions by chlorpheniramine the result of state dependency?

Conditioned flavor aversions induced by pairing flavored fluids with ionizing irradiation, lithium chloride, estrogen, or centrifugal rotation have been blocked by prior administration of chlorpheniramine. The blockade may be due to state dependency. This possibility was evaluated in the present experiment, which assigned female Long-Evans rats to a factorial combination of chlorpheniramine (20 mg/kg) vs saline during training, centrifugal rotation (150 rpm for 15 min) vs none as an UCS, and chlorpheniramine vs saline in testing. Rats conditioned with saline and rotation showed strong aversions when tested with either same or chlorpheniramine. Rats conditioned with chlorpheniramine and rotation showed no change during conditioning; when tested with saline they showed no aversion, and when tested with chlorpheniramine they showed no change from conditioning. Rats conditioned with either chlorpheniramine or saline and no rotation showed high fluid intake when tested with saline and reduced fluid intake when tested with chlorpheniramine. The results were interpreted as offering little support for state dependency.