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 familiarity and apomorphine-induced taste aversions in humans

Human volunteers learned taste aversions to a relatively novel cranberry flavor paired with apomorphine-induced illness. These aversions were significantly reduced by pretreatment familiarization to the flavor unless an unpalatable interfering flavor was introduced just prior to the administration of apomorphine. The outcomes have implications for taste-aversion learning in humans and for the control of flavor preferences in patients undergoing illness-inducing chemotherapy.     

Higher-order conditioning and sensory preconditioning of a taste aversion with an exteroceptive CS1

An exteroceptive stimulus compound (context) was employed as CS₁ in higherorder conditioning (H-OC, Experiments I and II), and sensory preconditioning (SPC, Experiment III) of a saccharin (CS₂) aversion in rats. The results indicated that aversions were established with the H-OC as well as with the SPC procedures. Stimulus generalization and first-order conditioning explanations were ruled out by appropriate controls. A CS₁-extinction period, performed prior to testing, did not affect the H-OC aversion, whereas it reduced the SPC aversion at least partially. These findings imply that interoceptive (taste, nausea) and exteroceptive stimuli (context) are readily associable in rats. Implications of the resemblance between the SPC procedure and long-delay taste-aversion learning are discussed.     

The influence of flavor preexposure and test interval on conditioned taste aversions in the rat

The effects of flavor preexposure and test interval on conditioned taste aversions were examined in four experiments. In the first three experiments, prior experience with a flavor different from that used as a conditioned-stimulus (CS) produced attenuated aversions when testing occurred after a 1-day interval but not after a 21-day interval. Preexposure to the same stimulus used as a CS produced attenuated aversions at both 1- and 21-day intervals. In Experiment 4, a delay interval between flavor preexposure and conditioning eliminated the attenuating effect of preexposure, but only when different stimuli were used for preexposure and conditioning. These data could not be easily accounted for by contemporary interpretations of preexposure as an event that interferes with subsequent acquisition of a conditioned aversion. An alternative retrieval interference hypothesis was outlined.     

Further Evidence that Social Interaction Reduces Conditioned Taste Aversions in Mice

Social interactions with other conspecifics affect food selection in mammals. A previous study suggested that male mice attenuate conditioned taste aversion (CTA) by lithium chloride after interacting with an unfamiliar male conspecific. The present study was designed to (a) examine whether interactions with a familiar conspecific would attenuate CTA and (b) investigate sex differences in the social attenuation of CTA in mice. Results indicated that interacting with a familiar conspecific of the same sex following poisoning attenuated conditioned taste aversions only in male mice. The results suggest that the familiarity of conspecifics was not a critical factor in the social attenuation of CTA. Discrepancies between present and previous findings are discussed.     

Effects of CS concentration in taste-aversion learning: Problems in assessing aversion strength

The concentration of saccharin (CS) solutions was varied between groups of rats in four taste-aversion learning experiments, using lithium chloride as the aversive agent (US). Saccharin intake was measured on four one-bottle presentations yielding data on initial taste neophobia as well as postconditioning aversion strength. The results indicated that saccharin intake declined progressively with increasing concentrations on the first presentation, and that preconditioning intake to a large extent predicted postconditioning intake. In an attempt to correct postconditioning values for differences of saccharin intake on the preceding trial, a taste suppression ratio (TSR) was computed as the quotient of the amounts of saccharin consumed by individual rats on consecutive presentations. In general, the TSR was found to be too insensitive to detect differences of conditioning strength acquired by different saccharin concentrations. Alternative approaches to the CS-concen-tration problem in taste-aversion learning are 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.     

Does Conspecific Fighting Yield Conditioned Taste Aversion in Rats?

Running in an activity wheel yields conditioned aversion to a taste solution consumed before the running, but its underlying physiological mechanism is unknown. According to the claim that energy expenditure or general stress caused by physical exercise is a critical factor for this taste-aversion learning, not only running but also other stressful exercises should yield conditioned aversion to the paired taste. This prediction was disconfirmed in two experiments, because stressful conspecific fighting did not work as an effective agent to establish taste aversion in rats.

     

Types of Food Aversions: Animal,Vegetable, and Texture

Despite a growing body of research investigating the origins and effects of food aversions, few research instruments have been developed to measure aversions to specific types or categories of food. Undergraduates (N = 209) responded to a series of food aversion questionnaires. The results suggest that people tend to be averse to 2 types of foods (vegetables and meats or fats) and to the texture and taste of certain foods (e.g., oysters). Aversions were slightly more prevalent among women than among men and were correlated with lower educational levels. The authors provide a means of advancing future research on this problem by reliably identifying 3 categories of food aversions. Future researchers should evaluate additional food categories and expand the focus on food aversions beyond the current concern with learned avoidance of specific food items.     

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.     

One-trial acquired likes and dislikes in humans: Disgust as a US,food predominance,and negative learning predominance

Self-reports were solicited by questionnaire on experiences in which likes or dislikes for anything except people were produced as a result of a single event. The same questionnaire also asked for cases of one-experience acquisition of, or loss of, fears. Analysis of 440 reports indicates that the learned taste aversion phenomenon accounts for most rapid acquired dislikes; foods were the subject of 77% of all rapid acquired dislikes. A new form of food “aversion” learning appeared (22 cases), in which the US is a disgusting stimulus rather than illness. This may be mediated by nausea, the same US as in illness-produced aversions. There were more than three times as many cases of one-trial dislikes as opposed to likes. This could result from a bias in remembering or sampling, a bias in the occurrence of events in the world, and/or a bias to learn more rapidly about negative events. In contrast to acquired likes and dislikes, foods were the subject of one-trial acquired fear in only 1 case out of 164.     

Developmental flavor experience affects utilization of odor, not taste in toxiphobic conditioning

Feeding experiences were varied in developing rats and the effects upon flavor neophobia and lithium chloride-induced flavor aversions were observed. In Experiment 1, nursing experience of neonate rats was reduced by artificial feeding via intragastric cannula; the rats then were tested with apple juice paired with lithium chloride injection at weaning or maturity. Conditioned aversions were not affected, but neophobia to novel apple juice was attenuated in artificially-reared rats tested at maturity. In Experiment 2, rats received enriched feeding experience after weaning, which consisted of (a) obtaining many complex flavors, a few of which were paired with poisoning, effortlessly in the home cage, or (b) foraging for various foods on an elevated maze. No dramatic effects on neophobia or conditioned taste aversion for saccharin water were apparent. In Experiment 3, rats were given experience after weaning with vanilla-scented water either paired or unpaired with quinine water, and then tested with the odor of almond or that odor compounded with saccharin water for neophobia and lithium-induced aversions. Flavor-experienced rats exhibited more pronounced odor conditioning and more resistance to extinction of the odor aversion after both simple and compound conditioning. In contrast, saccharin taste aversions were relatively unchanged. Apparently, enriched feeding and drinking experience facilitates the utilization of odor more than taste cues.     

Effect of preconditioning unconditioned stimulus experience on learned taste aversions.

One taste-aversion study using male Long-Evans rats in which ethanol was the unconditioned stimulus (UCS) and six studies in which lithium chloride (LiCl) was the UCS demonstrate that (a) exposure to the UCS prior to conditioning retards subsequent acquisition of learned taste aversions; (b) a single preconditioning UCS exposure is sufficient to attenuate conditioning; (c) the preconditioning UCS exposure must occur within a limited period prior to conditioning to attenuate learning; (d) repeated conditioning trials will override the effect of prior exposure to the UCS; (e) tolerance to the UCS is not a necessary condition for the attenuation effect to occur; (f) pairing the preconditioning UCS with a novel flavor other than the CS does not remove the preexposure effect, although it may reduce its magnitude; and (g) the degree of disruption is a positive function of preconditioning UCS dosage and an inverse function of conditioning UCS dosage.     

Learned safety and the CS-US delay gradient in taste-aversion learning

Decrements in taste-aversion learning produced by extensions of the interval between the CS flavor and poisoning (the US) may be attributed to decay of the CS trace during long CS-US intervals. Kalat and Rozin (1973) alternatively proposed that such decrements occur because during extended CS-US intervals subjects learn that the CS is safe. They sought to show that trace decay is not responsible for the CS-US delay gradient by demonstrating that learning is disrupted even if the CS is reintroduced during extended CS-US intervals. The present experiments show that such a second CS presentation during conditioning may (1) enhance subsequent intakes of the CS solution whether or not subjects are poisoned, and/or (2) facilitate aversion learning, the facilitation being greater the closer the second CS exposure is to poisoning. These results question the adequacy of previous evidence for the contribution of learned safety to the CS-US delay gradient and suggest that some other process is also involved.     

Taste aversions to mother's milk: the age-related role of nursing in acquisition and expression of a learned association.

The development of taste aversion learning to novel cues contained in mother's milk was examined in rat pups. Pups receiving distinctive mild by experimenter-delivered oral infusions followed by toxicosis formed an aversion to the dam's diet. Robust aversions were learned as early as Day 10 and were retained for at least 11 days. When the same distinctive milk was obtained directly from a foster mother through nursing, however, only weanling-age pups (over 20 days) formed an aversion. X-ray analysis of nipple location in the mouths of suckling pups suggested that pups between the ages of 10 and 21 days receive milk at a similar tongue locus. Flavored milk was then delivered at specific time intervals in controlled quantities through tongue cannulas implanted at loci corresponding to the nipple position shown by the X-rays. Cannulated preweanling pups that were attached to a nipple during milk delivery failed to associate the taste cue with illness, whereas both preweanlings off the nipple and weanlings on the nipple acquired aversions to the taste cue in the milk. The evidence obtained in these experiments suggests that pups of all ages are incapable of expressing a taste aversion in a nursing situation and that preweanling pups in particular are also dificient in acquiring aversions within a suckling context. The inability of preweanling pups to acquire taste aversions in a nursing situation appears to result from a failure to associate taste cues with illness rather than a failure to detect taste cues obtained from a nipple.     

An appraisal of chemical aversion (emetic therapy) approaches to alcoholism treatment.

More than 35,000 alcoholics have received chemical aversion (emetic therapy) in at least 75 settings worldwide since the 1930s. This consummatory aversion (CA) treatment, which pairs ethanol ingestion with emetically induced nausea, incorporates the highly efficient variety of learning known as taste aversion (TA) conditioning. The CA literature indicates that emetic therapy should induce conditioned alcohol aversions in many alcoholics. Such aversions have been widely reported by clinicians and have been confirmed by recent psychophysiological evidence. Long standing evidence of treatment effectiveness is found in the results of private hospitals which have consistently produced 1-yr abstinence rates approximating 60%. Diminished alcohol craving is a frequently reported benefit. Few experimental evaluations have been completed, as is generally the case for all alcoholism treatments, but those which used methodologically sound temporal parameters during conditioning have supported the clinical efficacy of emetic therapy. The clear need for more definitive research notwithstanding, there are compelling indications that emetic therapy is a useful component of multimodal treatment within certain alcoholic populations. However, its availability is severely limited. Many alcoholics could probably benefit from expanded treatment availability. The time is ripe for a reevaluation of resistances to the clinical use of emetic therapy alcoholism treatment.     

Formation of associations of colored and flavored food with induced sickness in five avian species

Domestic ducks, geese, pigeons, quail, and chickens were given colored, flavored, or colored and flavored food and then injected with lithium chloride. Each species showed learning of color and taste aversions. Flavor facilitated the formation of color aversions in ducks, geese, and pigeons but not in quail or chickens. Color interfered with the formation of flavor aversions in quail and chickens but not in the other three species. These findings indicate that all birds can probably associate both colored and flavored food with induced sickness and that colored food is more easily associated with induced sickness than is colored water. Moreover, these findings suggest that the capacity to associate colored and flavored food with induced sickness and the interaction between color and flavor in food vary between species. Birds, such as quail and chickens, that eat relatively tasteless food rely more on color than on flavor cues when forming learned food aversions. Birds that can select their food on the basis of taste, such as ducks and geese, rely more on flavor than on color when forming aversions to food. Birds, such as pigeons, that are initially raised on tasty food before switching to predominantly tasteless food show tendencies that are similar to those of ducks and geese.     

Conditioned taste and taste-potentiated odor aversions in the Syracuse high- and low-avoidance (SHA/Bru and SLA/Bru) strains of rats (Rattus norvegicus).

Syracuse high- and low-avoidance Long-Evans rats (Rattus norvegicus; SHA/Bru and SLA/Bru) were selectively bred for good and poor active-avoidance learning. However, SLA/Bru animals are superior to SHA/Bru rats in conditioned suppression and passive avoidance learning. In this experiment, saccharin taste and almond odor were the components of a compound conditioned stimulus (flavor) in an illness-induced aversive conditioning paradigm. SLA/Bru rats (n = 17) showed stronger conditioned flavor, taste, and odor aversion than did SHA/Bru animals (n = 18). Unselected Long-Evans rats (n = 18) were intermediate between the selected strains. SLA/Bru and Long-Evans rats showed taste-potentiated odor aversions in this experiment, whereas SHA/Bru animals did not. The results provide evidence that genetic factors, as exemplified by the different strains, are importantly involved in the mechanisms underlying interoceptive and exteroceptive aversive conditioning.     

Experimentally induced taste aversions in humans: effects of overshadowing on acquisition.

This study used vection-induced symptoms of motion sickness as an unconditioned stimulus to condition food aversions in humans and to evaluate the efficacy of an overshadowing agent (novel flavored candy: CS2) to attenuate acquisition of the aversion. Subjects unfamiliar with a target food (CS1) were assigned to one of the following three groups which were identical except for order of exposure to stimuli: Taste Aversion Group (CS1-US-CS2-Test), Control Group (US-CS1-CS2-Test), and Overshadowing Group (CS1-CS2-US-Test). Subjects were tested on aversion ratings and consumption of the target flavor and ratings of the overshadowing agent. Subjects in the Taste Aversion group rated the target flavor as significantly more aversive and consumed less of it, although not significantly so, that did those in the Control group. The Overshadowing group consumed significantly more of the target food than did the Taste Aversion Group. Considering only subjects unfamiliar with the overshadowing agent, those in the Overshadowing group rated the agent (CS2) as significantly more aversive than the Taste Aversion and Control groups. Implications of these findings to taste aversions in humans are discussed.