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Typically, the subjective pleasantness of an odor decreases after it has been repeatedly smelled. This study investigates how the pleasantness ("liking") and the wish to be further exposed to the same odor ("wanting") are affected by variety on a longer time scale, and how they relate to actual food intake. Twenty-five participants rated a coconut odor presented 120 times for its liking and wanting before being offered coconut sweets. The amount eaten was assessed. Individual patterns of change were described by fitting 3 different models to the ratings. To study effects of variety on odor evaluation, the ratings were compared with a previous study where coconut was 1 of 3 odors presented in an alternating way. Initially, both liking and wanting the odors were high, but decreased over repetitions in 75% of the subjects. About 40% of all subjects showed an exponential change of ratings, 40% a step-like change, and 20% a linear change. Food intake was not related to the pattern of change in the ratings. Moreover, decreased olfactory pleasure did not seem to affect eating behavior. However, participants who rated the coconut odor higher at the beginning ate twice as many sweets as the others. Odor variety did not affect the experienced pleasure of smelling (liking), but did affect the motivation to experience the same smell again (wanting). This has not been reported for food or touch stimulation and may be specific for the perception of odors.

It has been proposed that both positive and negative symptoms in schizophrenia (SZ) may derive, at least in part, from a disrupted ability to accurately and flexibly represent the value of stimuli and actions. To assess relationships between dimensions of psychopathology in SZ, and the tendency to devalue food stimuli, on which subjects were fed to satiety, we administered a sensory-specific satiety (SSS) paradigm to 42 SZ patients and 44 controls. In each of 2 sessions, subjects received 16 0.7-ml squirts of each of 2 rewarding foods and 32 squirts of a control solution, using syringes. In between the 2 sessions, each subject was instructed to drink one of the foods until he/she felt “full, but not uncomfortable.” At 10 regular intervals, interspersed throughout the 2 sessions, subjects rated each liquid for pleasantness, using a Likert-type scale. Mann-Whitney U-tests revealed group differences in SSS effects. Within-group tests revealed that, while controls showed an effect of satiety that was sensory specific, patients showed an effect of satiety that was not, devaluing the sated and unsated foods similarly. In SZ patients, we observed correlations between the magnitude of SSS effects and measures of both positive and negative symptoms. We argue that the ability to flexibly and rapidly update representations of the value of stimuli and actions figures critically in the ability of patients with psychotic illness to process salient events and adaptively engage in goal-directed behavior.

The current food supply in many parts of the world differs substantially from that which existed during most of human evolution. It is characterized by a high variety of palatable foods with high energy density and low fiber content. Many foods can be eaten very quickly, and there is not always congruency between the sensory properties of the food and the subsequent metabolic consequences of its ingestion, (e.g., as in the consumption of artificially sweetened foods). It is not presently known how the human body copes with this incongruent food environment in terms of short-term satiety responses and long(er)-term regulation of food intake. Cephalic phase responses (CPRs) are innate and learned physiological responses to sensory signals that prepare the gastrointestinal tract for the optimal processing of ingested foods. CPRs could be affected by inconsistencies in the associations between sensory signals and subsequent post-ingestive consequences. Reviewed here are the available data on how CPRs affect the control of food intake.

Sensory properties of food play an important role in satiation. Studies on the effect of taste intensity on satiation show conflicting results. This may be due to the notion that in these studies taste intensity and palatability were confounded. The objective of this study was to investigate the effect of salt intensity of tomato soup on ad libitum intake (satiation), while controlling for palatability on an individual basis. Forty-eight subjects consumed both a low-salt (LS) and high-salt (HS) soup ad libitum from a self-refilling bowl. The results showed no difference between LS and HS soup in ad libitum intake, eating rate, changes in appetite ratings, and changes in hedonic ratings after intake. After intake of HS soup, LS soup was perceived as more bland than before intake of HS soup. After intake of LS soup, HS soup was perceived as more salt intense than before intake of LS soup. In conclusion, this study found no effect of salt intensity on satiation of tomato soups that were similar in palatability. During consumption, subjects adapted quickly to the exposed salt intensity as contrasting salt intensities were rated further from the ideal salt intensity and therefore perceived as less pleasant after consumption.

Odor stimuli play an important role in the perception of food flavor. Olfactory dysfunction is thus likely to affect eating behavior. In the present study, we hypothesized that dysfunctional olfactory perception promotes sensory-specific satiety, a decrease in pleasure derived from a certain test food during and shortly after its consumption relative to other unconsumed control foods. A total of 34 hyposmic/anosmic participants were compared with 29 normosmic control participants. All participants repeatedly consumed a fixed portion of one and the same food item, a procedure known to induce sensory satiation. We found evidence for sensory-specific satiety (SSS) regardless of olfactory function. It thus appears that olfactory deficits have no major effect on SSS.

The acute effect of complexity in aroma composition on perceived satiation and food intake was investigated in 41 young, healthy, and normal weight subjects. Subjects consumed 2 different strawberry-aromatized sweetened yogurt products (i.e., test and placebo product) in either an olfactometer-aided or an ad libitum eating experimental design. The test product was aromatized with a multicomponent strawberry aroma, whereas the placebo product was aromatized with a single-component strawberry aroma. Compared to placebo, subjects felt significantly more satiated during aroma stimulation with the multicomponent strawberry aroma in the olfactometer-aided setting. Additionally, perceived satiation was significantly increased 10-15 min after consumption of the multicomponent strawberry-aromatized sweetened yogurt product in the ad libitum eating setting. There was no effect on the amount of strawberry-aromatized sweetened yogurt product consumed ad libitum. Apart from the differences in timing of the appetite-regulating effects, both experimental settings demonstrated that the multicomponent strawberry aroma, which was perceived as being more complex, yet of similar aroma quality, intensity, and pleasantness compared with the single-component strawberry aroma, was able to enhance perceived satiation. The methodology of the olfactometer-aided aroma stimulation proved to be representative of a real-life setting with regard to aroma exposure and satiation. Food products, which are perceived as being more complex, have been suggested to delay the development of sensory satiation as a result of implicitly cueing for variation. The present results may be explained by increased sensory stimulation, due to concurrent exposure to multiple aroma components cueing for sensorily similar strawberry perception.

ll animals, but especially omnivores such as rats and humans, face the seemingly daunting task of selecting a diet that supplies all of the essential nutrients. The complexity of factors that can affect food selection was out­lined in a recent review which listed the follow­ing influences on the appetite for specific foods: metabolic influences (eg, caloric requirements, neurotransmitter levels, hor­mones); specific appetites (eg, NaCI when salt-deficient); disease states (eg, diabetes, cancer); pharmacological influences (eg, ano­rectic drugs); environmental influences (eg, temperature); social influences (eg, culture, re­ligion); learned preferences and aversions; and hedonic factors (eg, palatability, taste, tex­ture, odor).

Single-neuron recording studies in non-human primates indicate that orbitofrontal cortex neurons represent the reward value of the sight, smell and taste of food, and even changes in the relative reward value, but provide no direct evidence on brain activity that is correlated with subjective reports of the pleasantness of food. In this fMRI investigation we report a significant correlation between the activation of a region of the human orbitofrontal cortex and the decrease in subjective pleasantness when a liquid food is eaten to satiety. Moreover, a cluster of voxels in the orbitofrontal cortex showed a decrease in its activation that was specific to the particular liquid food consumed in a meal, providing a neural correlate of sensory-specific satiety to a liquid whole food in humans. This sensory-specific reduction in activation of the orbitofrontal cortex correlating with subjective pleasantness is consistent with an important role for the orbitofrontal cortex in human emotion and motivation, and associated subjective states.