In summary, using a short period of ethanol exposure and a brief deprivation period the results revealed a direct relationship between chronological age and propensity to consume alcohol, being the adolescence a transition period from the infant to the adult pattern of alcohol consumption. Preadolescent animals showed the highest ethanol consumption level. The ADE was only found in adult animals for both alcohol consumption and preference, whereas adolescents showed an ADE only for preference. No effect of sex was detected in any phase of the experiment.

Differences in food consumption among body-weight statuses (e.g., higher fruit intake linked with lower body mass index (BMI) and energy-dense products with higher BMI) has raised the question of why people who are overweight or are at risk of becoming overweight eat differently from thinner people. One explanation, in terms of sensitivity to affective properties of food, suggests that palatability-driven consumption is likely to be an important contributor to food intake, and therefore body weight. Extending this approach to unpalatable tastes, we examined the relationship between aversive reactions to foods and BMI. We hypothesized that people who have a high BMI will show more negative affective reactions to bitter-tasting stimuli, even after controlling for sensory perception differences. Given that hedonic reactions may influence consumption even without conscious feelings of pleasure/displeasure, the facial expressions were included in order to provide more direct access to affective systems than subjective reports. Forty adults (28 females, 12 males) participated voluntarily. Their ages ranged from 18 to 46 years (M=24.2, SD=5.8). On the basis of BMI, participants were classified as low BMI (BMI<20; n=20) and high BMI (BMI>23; n=20). The mean BMI was 19.1 for low BMI (SD=0.7) and 25.2 for high BMI participants (SD=1.8). Each subject tasted 5 mL of a grapefruit juice drink and a bitter chocolate drink. Subjects rated the drinks' hedonic and incentive value, familiarity and bitter intensity immediately after each stimulus presentation. The results indicated that high BMI participants reacted to bitter stimuli showing more profound changes from baseline in neutral and disgust facial expressions compared with low BMI. No differences between groups were detected for the subjective pleasantness and familiarity. The research here is the first to examine how affective facial reactions to bitter food, apart from taste responsiveness, can predict differences in BMI.

The present study investigated the decrement in nutrient-based conditioned flavor preference found in hungry rats exposed to a flavor following simultaneous flavorsucrose conditioning while thirsty. Although a significant decrease in preference was found in the experimental group in each experiment, there was no evidence of either spontaneous recovery (Experiment 1) or reinstatement (Experiment 2). In addition, posttraining flavor exposure weakened the original flavor-sucrose association (Experiment 3). These results suggested that the flavor-US association might have been impaired after posttraining flavor exposure. Two further experiments assessed whether the flavor acquired the properties of a net inhibitor, using the retardation and summation tests for conditioned inhibition. Experiment 4 revealed that the flavor suffered retardation when retraining was conducted after the exposure phase. In Experiment 5, the target flavor decreased the preference shown for a different flavor previously paired simultaneously with sucrose when both were presented forming an unreinforced compound in the summation tests. None of these effects was found in a control group, which had received serial flavor → nutrient presentations during training. Together, these results suggest that a flavor simultaneously paired with sucrose acquires the properties of a net inhibitor when it is subsequently presented outside the compound to hungry animals.Keywords Conditioned inhibition . Extinction . Flavor preference . Retardation test . Summation test Conditioned flavor preference (CFP) is considered a form of Pavlovian conditioning (Rozin & Schulkin, 1990;Rozin & Zellner, 1985). A simple procedure for establishing this learning is to allow rats to drink a neutral flavor (the conditioned stimulus [CS]) paired with either a palatable second flavor (e.g., Holman, 1975) or a nutrient presented orally or intragastrically (e.g., Capaldi, Campbell, Sheffer, & Bradford, 1987;Sclafani & Nissenbaum, 1988), which serves as the unconditioned stimulus (US). These pairings result in a preference being established for the CS + (flavor paired with US) over CS-(flavor unpaired with US) (e.g., Drucker, Ackroff, & Sclafani, 1994;Lucas & Sclafani, 1989), as well as for the CS + over plain water (e.g., Harris, Gorissen, Bailey, & Westbrook, 2000;Pérez, Lucas, & Sclafani, 1998).An unusual property attributed to learned flavor preferences, established either by combining the flavor with a palatable taste or by following ingestion of the flavor with a nutrient, is their resistance to extinction (e.g., Albertella & Boakes, 2006;Capaldi, Myers, Campbell, & Sheffer, 1983;Drucker et al., 1994;Elizalde & Sclafani, 1990;Fedorchak, 1997;Sclafani, 1991). Nevertheless, it has been possible to observe the effects of flavor-alone presentations on CFP after conditioning with more sensitive testing procedures. Harris, Shand, Carroll, and Westbrook (2004, Experiments 2A and 2B) examined conditioned preference in rats simultaneously exposed to a target flavor and sucr...

Preferences for and consumption of bitter foods such as vegetables and fruit are 28 important in addressing the epidemic of obesity as healthy dietary patterns contribute to its 29 prevention. However, few studies have been undertaken to understand the preference for 30 bitter-tasting foods. A generally accepted but not proven explanation is that these acquired 31 preferences involve changes in affective and motivational processes in order to overcome the 32 innate rejection of bitter tastes. To examine this issue we compared the hedonic and incentive 33 responses to bitter substances among bitter likers and dislikers. In addition, the effects of 34 hunger, stress and weight concern on bitter preferences were also explored. Fifty-nine healthy 35 adults (age = 24.8 ± 6.3; body mass index = 22.0 ± 2.8) were divided into bitter likers and 36 bitter dislikers according to their food preferences. Both groups sampled the unreinforced 37 flavours of coffee, beer, chocolate and grapefruit under four motivational states induced by 38 static pictures (neutral, food, stressor and obesity) at the time of testing. The results showed 39 that the bitter solutions elicited less aversive responses (higher hedonic ratings and less 40 intense disgust reactions) and fewer avoidance behaviours (slower response time and lower 41 amount of water for rinsing) in bitter likers after viewing neutral images. On the other hand, 42 likers exhibited a further reduction in disgust to coffee after viewing stressor pictures, and 43 also drank more water after tasting chocolate following the obesity pictures, compared with 44 the dislikers. The expression of disgust increased in bitter likers, as well as the amount of 45 water used to rinse the mouth, after tasting chocolate following pictures showing obesity 46 compared with pictures showing food. These results show, for the first time, not only the 47 implication of affective and incentive components in reversal of the predisposition to reject 48 bitterness but also the motivational modulation of the expression of rejection of bitter tastes 49 in humans.

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Emotional eating (EE) corresponds to a change in eating behavior in response to distress and results in an increase of food intake (overeating (EOE)) or in food avoidance (undereating (EUE)). EE has been related to temperament (i.e. negative emotionality) and dysregulated stress biomarkers in school-aged children; parenting has been understood to influence this relationship in older children. The aim of the study was to investigate to which extent stress biomarkers and negative emotionality are related to EE and to understand the role of parenting in this relationship. The sample consisted of 271 children aged 2-6 years of the Swiss cohort study SPLASHY. We assessed the child's EE, negative emotionality and parenting by parent based reports. Salivary samples were collected over two days to analyze cortisol and salivary alpha-amylase levels. From the whole sample of children, 1.1% showed EOE and 32.9% EUE. Negative emotionality was related to EOE and EUE (0.13 (CI 0.06, 021), p < 0.001; 0.25 (CI 0.14, 0.35), p < 0.001). There was no relationship between stress biomarkers and EE and parenting had any moderating role (all p > 0.05). Similar to a Danish study, parents reported more often EUE than EOE of their child. Both are related to the temperament. Even though the course of EE has not yet been well documented, we conclude that a certain subgroup of children with difficult temperament could be at-risk for eat and weight regulation problems in later childhood.

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