A COMPUTERIZED SYSTEM FOR CONTROLLING AND MEASURING GUSTATORY REACTION TIMES

Time-intensity and reaction-time methodology applied to the dynamic perception and liking of bitterness in relation to body mass index

There are very few studies which have considered perception temporality when relating perceived intensity and hedonic responses in relation to body mass index (BMI; kg/cm²). The aim of the present study was to determine the relationship between BMI with the dynamic perception and liking of bitter tasting solutions. For this purpose, two different categories of bitter products were applied: 6-n-propilthiouracil (PROP) solutions (0.010, 0.032 and 0.060 mmol/L) and commercial beverages (coffee, yerba mate infusion and grapefruit juice). The proposed methodology to evaluate perception and hedonic response was based on the measurement of reaction-time (R-T) and multiple-sip time-intensity (T-I) registers in people with a high BMI (25 < BMI < 30; overweight group) and a normal BMI (<25; normal-weight control group). The multiple-sip evaluation to describe perception of PROP solutions and liking of beverages was used as a more ecologically valid laboratory methodology to simulate a situation of usual consumption. In this sense, working with a multiple-sip design helped confirm that bitter taste has a cumulative effect since in every case the sip effect was significant when evaluating the maximum intensity; this effect was more important as the bitterness increased. Regarding the body weight group comparisons, the normal BMI group perceived bitter taste more intensely and the time to react to it was shorter (faster reaction) for both PROP solutions and the three beverages. Interestingly, even though the high BMI group rated the bitter taste as less intense, they had a lower level of acceptance than normal BMI. This result suggests that the hedonic rather than the sensory component might be playing a crucial role in the perception of bitter taste in individuals with high BMI.

Facial affective reactions to bitter-tasting foods and body mass index in adults

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.

Comparison times are longer for hedonic than for intensity judgements of taste stimuli

Response times of intensity and hedonic comparisons were determined in a within-subjects experimental design. Forced-choice paired comparisons of orange lemonades with various concentrations of added quinine sulfate were made by 48 subjects. Depending on experimental condition, the subjects had to focus either on intensity or on pleasantness and give their responses as fast as possible. The data showed shorter response times for intensity comparisons than for pleasantness comparisons. Although taste processing may be partially serial and partially parallel, the larger part of the response times and the differences between them may be due to cognitive processing.

The Temporal Automated System for Taste Experiments (TASTE)

We describe a new, open flow device for presenting taste stimuli to human subjects under controlled conditions of timing. The device delivers each stimulus as a mist to the participant's tongue through one of 16 nozzles attached to a linear slide. Software controls the position of the slide, the duration of the stimulus, and the duration of the pre- and poststimulus water rinses and records the responses of the participant. Temporal characteristics of this system make it especially applicable to studies on the role of attention in taste perception.