Motivational state modulates the hedonic value of food images differently in men and women

Abstract

We investigated visual alimentary alliesthesia in non-fasted ($N=369$) and fasted participants ($N=257$) viewing photographs of food. Fasted participants were asked to not eat for 12 h before the session. Each participant was shown food and non-food images and rated each image on valence (i.e., pleasantness). The strongest evidence of alliesthesia was found in women. Fasting enhanced the pleasantness of food images for each of the food categories in women, although this alliesthesia effect was smaller in response to dessert foods compared to the less-pleasantly-rated food categories. In addition, non-fasting women exhibited significant positive correlations between hunger ratings and valence ratings of three of the five food categories. There was no significant difference in valence ratings of food between fasting vs. non-fasting men, but non-fasting men showed correlations between hunger and valence that were similar to those observed among the women. No evidence was found of hunger- or fasting-induced enhancement of hedonic ratings of non-foods in women or men, indicating the specificity of the alliesthesia effect for the food images only.

Introduction

Emotional reactions to foods are important influences on food intake. Prior research has shown, for example, that hedonic value, as assessed by valence ratings of gustatory stimuli, is predictive of amount consumed and food preferences (e.g., Caltabiano & Shellshear, 1998; McCrory, Saltzman, Rolls, & Roberts, 2006). The hedonic value of a food is modulated by the motivational state of an organism, a phenomenon termed “alliesthesia” (Cabanac, 1971; Winkielman & Berridge, 2003). Studies presenting gustatory stimuli to participants have shown that foods can either be perceived as pleasant during a state of hunger or unpleasant or neutral during a state of satiety (Blundell & Hill, 1988; Cabanac, 1979; Fantino, 1984; Frankham, Gosselin, & Cabanac, 2005; Laeng, Berridge, & Butter, 1993; Rolls, Rolls, & Rowe, 1983). Effects of internal state on hedonic value of visual food cues, e.g., the sight of food or of food pictures, have been studied less often, although affective reactions to visual food cues are also important factors in determining future intake, influencing such variables as the probability of the initiation of eating and food choices (Marcelino, Adam, Couronne, Koster, & Sieffermann, 2001; Rolls, Rowe, & Rolls, 1982; Rolls et al., 1983).

Fundamental questions remain about the robustness of alliesthesia with visual stimuli, possible gender differences, its specificity for foods vs. non-foods, and its generality across food categories. Thus, for example, two studies using samples of men and women reported that hungry participants rated food pictures or the sight of food as more pleasant than sated participants did (Rolls et al., 1983; Uher, Treasure, Heining, Brammer, & Campbell, 2006). On the other hand, Drobes et al. (2001) did not find that valence ratings of food pictures were increased by food deprivation in a mixed sample of men and women, but did obtain positive results in a second study with only female participants. In none of these studies were valence ratings of non-foods higher in the fasted compared to the non-fasted state. These outcomes suggest the motivational specificity of alliesthesia, an important property if it is to be useful in guiding behavior. However, the only non-foods tested by Rolls et al. (1983) were water and a low-calorie orange-flavored beverage. Because the motivations to consume foods vs. fluids are closely linked—reciprocally in some circumstances (e.g., hunger reduces motivation to drink; Bolles, 1975) this finding cannot address whether hedonic values of non-foods in general are unaffected by fasting. The other two studies cited above used a wider variety of non-food stimuli, but nonetheless used relatively small sets of stimuli and did not systematically examine different categories of non-foods (Drobes et al., 2001; Uher et al., 2006).

Little is known about the generality of alimentary alliesthesia. Whether test stimuli have been gustatory or visual, they have typically represented foods high in palatability, such as sweet solutions, desserts, and high-fat snacks (e.g., Cabanac, 1979; Drobes et al., 2001; Laeng et al., 1993; Rolls et al., 1983; Uher et al., 2006). Thus, it is not known whether magnitude of alliesthesia varies systematically as a function of type of food.

We have addressed the above issues by comparing valence ratings by fasted and non-fasted participants using an extensive catalog of pictures of foods and non-foods. Our aim was to provide a rigorous test of this form of visual alliesthesia with systematic comparisons of results from men vs. women as well as evaluation of both its generality across several categories of foods and its specificity by providing several categories of non-foods for comparison.