Expression of flavor preference depends on type of test and on recent drinking history.

The persistence of a conditioned flavor preference was examined in 3 experiments. All contained an initial acquisition phase in which half the rats were given almond odor mixed with sucrose (AS) in some sessions and water (W) only in other sessions, whereas the other half (controls) were given explicitly unpaired exposures to almond (A) and sucrose (S) in separate sessions. Subsequent 2-bottle choice tests revealed a persistent preference for A, despite extinction exposure to A or S, but this depended on the choice offered on test: Exposure to A did not extinguish the preference for A over W but did reduce the preference for AS over S; conversely, exposure to S did not extinguish the preference for AS over S but did reduce the preference for A over W. These results indicate that flavor preferences can be resistant to extinction procedures but suggest that the expression of such preferences in choice tests depends on an adaptation-level process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interactions between conditioned and unconditioned flavor preferences.

Five experiments investigated how rats' conditioned preferences or aversions for aqueous odors paired with sucrose or salt are affected by their unconditioned response to those tastes. Rats preferred an odor paired with 30% sucrose over an odor paired with 5% sucrose when both were presented in 5% sucrose, but they showed no preference or, if thirsty, showed the reverse preference, when the odors were presented in 30% sucrose. These changes in conditioned preference corresponded to changes in the rats' unconditioned preference for the accompanying sucrose solution. Rats' conditioned aversions for odors paired with salt showed a similar dependence on their reaction to the accompanying salt solution. The results were interpreted as showing that conditioned and unconditioned flavor preferences combine additively, as if mediated by the same sensory representation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Amphetamine and morphine produce a conditioned taste and place preference in the house musk shrew (Suncus murinus).

Rats have been shown to avoid consuming a flavor, but prefer a location, previously paired with amphetamine or morphine. A series of 4 experiments evaluated the hedonic properties of amphetamine and morphine in the house musk shrew (Suncus murinus), an insectivore that (unlike rats) is capable of vomiting when exposed to toxins. Unlike rats, amphetamine (20 mg/kg) and morphine (20 mg/kg) produced both a conditioned sucrose (0.3 M) and saccharin (0.1%) preference in shrews (administered intraperitoneally), when measured by both a 1-and a 2-bottle test. At the same dose, both drugs also produced a place preference in shrews. These results suggest that the potential of rewarding drugs to produce taste avoidance may vary on the basis of the ability of the species to vomit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reinforcer devaluation in palatability-based learned flavor preferences.

Rats exposed to simultaneous compounds of 1 neutral flavor with dilute (2%) sucrose and a 2nd flavor with dilute (2%) maltodextrin subsequently consumed both flavors in preference to a 3rd flavor that was never paired with a palatable taste. Brief training exposure under ad lib food and water minimized the postingestive effects of nutrients, emphasizing the contribution of palatability to these preferences. Devaluation of sucrose or maltodextrin by pairing with illness (Experiment 1) or sensory-specific satiety (Experiment 2) selectively reduced the preference for the flavor previously paired with the devalued reinforcer. Such reinforcer-specific devaluation effects suggest that palatability-based learned flavor preferences are underpinned by a Pavlovian process whereby the cue flavor is associated with the taste of the concurrently consumed palatable reinforcer. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extinction of conditioned flavor preferences.

In a series of 4 experiments, the effects of extinction on flavor preferences conditioned by mixing flavor cues with a nutrient were examined. In each experiment it was observed that rats preferred a flavor cue that had not undergone extinction to one that had. In addition, this preference was reversed in subjects trained thirsty (Experiments 1 and 2) if the associated nutrient had been devalued prior to the test or the preference for the nonextinguished cue was attenuated by nutrient devaluation in subjects trained hungry (Experiments 3 and 4). The results suggest that extinction may weaken associations between the flavor and the specific sensory properties of the nutrient and, for subjects trained hungry, between the flavor and the motivational components of the nutrient as well. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned flavor preferences based on delayed caloric consequences.

In four experiments we showed that rats prefer a flavor associated with a delayed edible consequence if the delayed consequence contains calories; the greater the number of calories, the greater the preference. We obtained conditioned preferences with delayed consequences of dextrose plus quinine, 8% polycose, 8% sucrose, 10 g of high fat mash, and 14 g of lab chow. No conditioned preferences were obtained with delayed consequences of saccharin, 10 g of low fat mash, 1% polycose, or 1% sucrose. Thus, it seems that flavor preferences based on delayed caloric consequences occur only if there are appreciable calories in the consequence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex versus sweet: Opposite effects of opioid drugs on the reward of sucrose and sexual pheromones.

Endogenous opioids mediate some reward processes involving both natural (food, sweet taste) and artificial (morphine, heroin) rewards. In contrast, sexual behavior (which is also reinforcing) is generally inhibited by opioids. To establish the role of endogenous opioids for a newly described natural reinforcer, namely male sexual pheromones for female mice, we checked the effects of systemic injections of the general opioid antagonist naloxone (1-10 mg/kg) and the agonist fentanyl (0.1- 0.5 mg/kg) in a number of behavioral tests. Naloxone affected neither the innate preference for male-soiled bedding (vs. female-soiled bedding) in 2-choice tests nor the induction of place conditioning using male pheromones as rewarding stimuli, although it effectively blocked the preference for consuming a sucrose solution. In contrast, fentanyl inhibited the preference for male chemosignals without altering sucrose preference. These results suggest that, in macrosmatic animals such as rodents, opioidergic inhibition of sexual behavior might be due, at least partially, to an impaired processing of pheromonal cues and that the hedonic value of sweet-tasting solutions and sexual pheromones are under different opioid modulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

I want to be creative: Exploring the role of hedonic contingency theory in the positive mood-cognitive flexibility link.

Three studies explored the role of hedonic contingency theory as an explanation for the link between positive mood and cognitive flexibility. Study 1 examined the determinants of activity choice for participants in happy, sad, or neutral moods. Consistent with hedonic contingency theory, happy participants weighted potential for creativity as well as the pleasantness of the task more heavily in their preference ratings. In Study 2, participants were given either a neutral or mood-threatening item generation task to perform. Results illustrated that happy participants exhibited greater cognitive flexibility in all cases; when confronted with a potentially mood-threatening task, happy participants were able to creatively transform the task so as to maintain positive mood and interest. Finally, Study 3 manipulated participants' beliefs that moods could or could not be altered. Results replicated the standard positive mood-increased cognitive flexibility effect in the nonmood-freezing condition, but no effects of mood on creativity were found in the mood-freezing condition. These studies indicate that the hedonic contingency theory may be an important contributing mechanism behind the positive mood-cognitive flexibility link. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual Learning Enhances Retrospective Revaluation of Conditioned Flavor Preferences in Rats.

Forward and backward blocking of taste preference learning was compared in rats. In the forward condition, thirsty rats were exposed to a flavor (A) in sucrose solution (+) or in water (-), after which they were exposed to A in compound with another flavor (B) in sucrose solution (i.e., AB+). In the backward condition, these phases were reversed. Consumption of B alone was assessed when rats were food deprived. In the forward condition, rats given A+ consumed less B than rats given A-, providing evidence of forward blocking, whereas in the backward condition, rats given A+ drank more of B than those given A-. Subsequent experiments found that alternating but not blocked preexposure to A and B, when given prior to training, produced blocking of B whether A+ was given before or after AB+, suggesting that prior failures to observe backward blocking reflect failures of discrimination. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motivational state regulates the content of learned flavor preferences.

Rats acquired a preference for an aqueous odor (almond) presented in simultaneous compound with sucrose. Separate presentations of saccharin reduced this preference in rats with ad-lib access to food during training or at test, but not in rats that were hungry during both training and test. In contrast, separate presentations of sucrose reduced the preference for the almond irrespective of deprivation state during training and test. We interpret the results to mean that a hungry rat forms odor–taste and odor–calorie associations, and its motivational state on test determines which of these associations controls the preference. In contrast, a rat that is not hungry during training only forms an odor-taste association, and its performance on test is independent of its level of hunger. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Muscarinic receptor antagonism of the nucleus accumbens core causes avoidance to flavor and spatial cues.

Pharmacological blockade of muscarinic receptors in the nucleus accumbens reduces food intake and instrumental behaviors that are reinforced by food delivery. Nucleus accumbens muscarinic antagonism may specifically suppress the hedonic or reinforcing effects of food, thus blocking its capacity to direct behavior. Alternatively, muscarinic receptor blockade may cause a negative hedonic state that interferes with appetitive learning and food intake. In these experiments, rats received infusions of scopolamine methyl bromide (10 μg/0.5 μl) into the nucleus accumbens core, following exposure to a novel flavor of liquid diet (Experiment 1) or prior to being placed into a place preference apparatus (Experiment 2). In both experiments, nucleus accumbens muscarinic receptor antagonism caused subsequent avoidance of the paired cue (flavor or spatial location). This effect was specific to cholinergic manipulation; no conditioned taste avoidance was observed after pairing the novel flavor with nucleus accumbens core antagonism of N-methyl-D-aspartate, dopamine D?, or opioid receptors (Experiment 3). These experiments confirm previous reports of a critical role for striatal acetylcholine in modulating goal-directed behaviors, but suggest caution when interpreting behavioral effects of pharmacological manipulation of striatal acetylcholine. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cue interactions in flavor preference learning: A configural analysis.

[Correction Notice: An erratum for this article was reported in Vol 37(2) of Journal of Experimental Psychology: Animal Behavior Processes (see record 2011-08162-003). There was an error in Figure 3, which is described in the correction.] Four experiments showed that the preference normally established to a neutral flavor cue that was paired with maltodextrin was attenuated when that cue was conditioned in compound with another flavor—overshadowing. Furthermore, two experiments showed that the preference for a neutral flavor conditioned as part of a compound was further attenuated if the other element in that compound was separately paired with the reinforcer—blocking. These results stand in contrast to a number of previous compound flavor preference conditioning experiments, which have not revealed reliable cue competition effects. These discrepant findings are discussed in terms of the effects of within-compound associations and a configural perspective on potentiation. Modeling of this configural perspective predicts that a compound of two separately trained cues will elicit a similar response to the individual cues themselves—absence of summation. Two experiments confirmed this prediction. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Hedonic and sensory characteristics of odors conditioned by pairing with tastants in humans.

Animals readily acquire positive odor-taste hedonic associations, but evidence for this in humans remains weak and was explored further. Retronasal pairing of odors with sucrose or salty stimuli (Experiment 1) increased the rated sweetness of sucrose-paired odors without altering liking, although changes in odor pleasantness correlated with sucrose liking. Experience of odors with sucrose or quinine by sweet likers (Experiment 2) found increased pleasantness and sweetness for sucrose-paired odors, whereas quinine-paired odors became less liked and more bitter. Odor-sucrose pairings in sweet likers and dislikers (Experiment 3) found increased sweetness in both groups but increased odor liking only in likers. These data suggest that evaluative and sensory learning are dissociable and that evaluative changes are sensitive to individual differences in sweet liking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Cue interactions in flavor preference learning: A configural analysis": Correction to Dwyer et al. (2011).

Reports an error in "Cue interactions in flavor preference learning: A configural analysis" by Dominic M. Dwyer, Mark Haselgrove and Peter M. Jones (Journal of Experimental Psychology: Animal Behavior Processes, 2011[Jan], Vol 37[1], 41-57). There was an error in Figure 3. The X-axis of both panels of this figure should be labeled “3-trial block” and not “trial.” The analysis of the simulations presented in Figure 3 are unaffected by this change. The corrected figure is provided in the erratum. (The following abstract of the original article appeared in record 2011-01268-001.) Four experiments showed that the preference normally established to a neutral flavor cue that was paired with maltodextrin was attenuated when that cue was conditioned in compound with another flavor—overshadowing. Furthermore, two experiments showed that the preference for a neutral flavor conditioned as part of a compound was further attenuated if the other element in that compound was separately paired with the reinforcer—blocking. These results stand in contrast to a number of previous compound flavor preference conditioning experiments, which have not revealed reliable cue competition effects. These discrepant findings are discussed in terms of the effects of within-compound associations and a configural perspective on potentiation. Modeling of this configural perspective predicts that a compound of two separately trained cues will elicit a similar response to the individual cues themselves—absence of summation. Two experiments confirmed this prediction. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Negative anticipatory contrast and preference conditioning: Flavor cues support preference conditioning, and environmental cues support contrast.

In 2 experiments, access to a .15% saccharin solution was followed on alternating days by access to a 32% sucrose solution and the same saccharin solution. In Exp 1, rats increased both intake of and preference for a flavored saccharin solution that predicted sucrose, but neither effect was found using a predictive odor cue alone. Exp 2 replicated the predictive flavor results but showed suppression of saccharin intake when environmental cues predicted sucrose. When both flavor and environment predicted sucrose, saccharin intake did not change, but preference for the predictive flavor increased. Discriminative taste cues appear to facilitate the development of preference conditioning, but environmental cues favor negative anticipatory contrast effects. Also, preference conditioning and contrast may develop concurrently and compete for expression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hunger enhances the expression of calorie- but not taste-mediated conditioned flavor preferences.

Compared ethanol-mediated flavor preferences to preferences mediated by saccharin, which is sweet but noncaloric, and sucrose, which is both sweet and caloric in 4 experiments, using 74 Long-Evans rats. Ss learned to associate grape or orange flavor conditioned stimulus/stimuli (CS) with (1) ethanol or saccharin solution or (2) either the other unconditioned stimulus/stimuli (UCS) or plain tap water. They were then given 2-bottle choice tests between the flavor CSs apart from the UCSs. Flavors associated with 5% ethanol were preferred over saccharin-paired and water-paired flavors by sated Ss, and food deprivation during the choice test enhanced this preference. Flavors associated with 8% sucrose were preferred over water-paired flavors, and this preference was also enhanced by food deprivation. Flavors associated with 0.028% or 0.25% saccharin were preferred over flavors paired with water. In all cases, calorie-mediated preferences, at their highest levels, were stronger than taste-mediated preferences. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Morphine- and naltrexone-induced modification of palatability: Analysis by the taste reactivity test.

Used the taste reactivity (TR) test, a direct measure of the hedonic properties of a tastant, to assess in Sprague-Dawley rats the ability of morphine (an opiate agonist) and naltrexone (an opiate antagonist) to modify the palatability of a bitter quinine solution and a sweet sucrose solution. Morphine reduced the aversive hedonic properties of both novel and familiar quinine solution (0.05% and 0.1%) but did not modify the palatability of 20% sucrose solution. Naltrexone reduced the positive hedonic properties of sucrose solution (2% and 20%) but did not modify the palatability of 0.05% quinine solution. The pattern of results suggests that the modification of feeding produced by opiate agonists and antagonists may be mediated by a hedonic shift in the palatability of the tastant. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Potentiation and overshadowing in preweanling and adult rats.

Four experiments that compared the aversion acquired by 599 18- and 60-day-old Sprague-Dawley rats to a flavor that was either tasted alone or in combination (simultaneously or successively) with another flavor when paired with illness were conducted to study temporal variables and theoretical issues pertinent to potentiation and overshadowing while investigating ontogenetic differences in these phenomena. Results show that when either preweanlings or adults were presented with a simultaneous compound flavor (sucrose/coffee) followed by LiCl-induced illness, greater sucrose aversions were found than for Ss conditioned on sucrose alone. Preweanlings demonstrated greater potentiation than adults, whether the CS–UCS delay was 0 or 1 hr. This potentiation was eliminated by nonreinforced presentations of the alternative CS element. Potentiation was not observed when the 2 flavors were presented successively as the CS; instead, overshadowing occurred. Tests of configuring by extinction procedures indicated a tendency for these Ss to form a configured representation of the simultaneous compound solution. This disposition for configuring was more pronounced for preweanlings than for adults. Ontogenetic differences in response to configuration, CS saliency, and generalization decrement were consistent with the observed ontogenetic differences in potentiation. (33 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

LSD produces place preference and flavor avoidance but does not produce flavor aversion in rats.

The hedonic properties of lysergic acid diethylamide (LSD) were assessed using the place conditioning, taste reactivity, and taste avoidance tests. LSD produced a conditioned place preference, but only at the highest dose tested (0.2 mg/kg). A single preexposure to the conditioning chamber (latent inhibition) prevented the establishment of a place preference. When paired with sucrose, doses of 0.05 to 0.2 mg/kg of LSD produced taste avoidance, but no dose of LSD produced an aversion to the taste as assessed by the taste reactivity test. These results suggest that LSD, like other rewarding drugs, produces taste avoidance by a mechanism other than that produced by emetic drugs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)