Effects of different food hardness on cognitive inhibitory control function.

Mastication leads to an immediate enhancement in cognitive functions, including inhibitory control. Furthermore, the hardness of the food increases sympathetic nerve activity during and immediately after mastication. Hence, the cognitive function could be enhanced by increased sympathetic nerve activity. The present study aimed to investigate the effects of food hardness on cognitive inhibitory control function in humans. The participants were 23 healthy adults (19-22 years old). Experiments were conducted with two types of gummies (soft and hard). The participants ingested 13 g of gummies and performed a stop-signal task to measure cognitive inhibitory control function after they rested for 5 min. The reaction time for the stop-signal task after gummy consumption was significantly shorter in the hard gummy condition compared to the soft gummy condition (p < .05). Furthermore, the accuracy rate of the responses was also significantly higher in the hard gummy condition compared to the soft gummy condition (p < .05). The results of the present study suggest that food hardness enhances cognitive inhibitory control function in humans.

Cross-modal and subliminal effects of smell and color.

In the present study, we examined whether the cross-modal effect can be obtained between odors and colors, which has been confirmed under olfactory recognizable conditions and also occurs under unrecognizable conditions. We used two flavors of red fruits such as strawberries and tomatoes for this purpose. We also aimed to compare whether similar cross-modal effects could be achieved by setting the flavors at recognizable (liminal) and unrecognizable (subliminal) concentrations in the experiment. One flavor at a normal concentration (0.1%, Liminal condition) and one at a concentration below the subliminal threshold (0.015%, Subliminal condition), were presented, and the color that resembled the smell most closely from among the 10 colors, was selected by participants. Except for the subliminal tomato condition, each odor was significantly associated with at least one color (p < 0.01). Participants selected pink and red for liminal strawberry (0.1%) (p < 0.05), pink for subliminal strawberry (0.015%) (p < 0.05), and orange for liminal tomato (0.1%) (p < 0.05), but there was no color selected for subliminal tomato (0.015%) (p < 0.05). The results of this study suggest that the flavor of tomato produced a cross-modal effect in liminal conditions, but not in subliminal conditions. On the other hand, the results of the present study suggest that the flavor of strawberries produces a cross-modal effect even under subliminal conditions. This study showed that cross-modal effects might exist, even at unrecognizable levels of flavor.

The effect of background music tempo on eating speed and food intake volume within in healthy women.

BACKGROUND: The effects of the different tempos of background music (BGM) on food intake and eating speed have not been fully studied. AIM: The study aimed to investigate the influence of changing the tempo of BGM during meals on food intake and to explore strategies to support appropriate eating behavior. METHODS: Twenty-six healthy young adult women participated in this study. In the experimental phase, each participant ate a meal under three separate conditions: fast (120% speed), moderate (original, 100% speed), and slow (80% speed) BGM. The same music was used for each condition, and appetite before and after eating, the amount of food consumed, and eating speed were recorded. RESULTS: The results showed that food intake (g, mean ± standard error (SE)) was slow: 317.9 ± 22.2, moderate: 400.7 ± 16.0, and fast: 342.9 ± 22.0. Eating speed (g/s, mean ± SE) was slow: 28.1 ± 2.8, moderate: 34.2 ± 2.7, and fast: 27.2 ± 2.4. The analysis showed that the moderate condition showed greater speed than the fast and slow conditions (slow-fast: p = .008; moderate-slow: p = .012; moderate-fast: p = .004). Moreover, the food intake in the moderate condition was significantly higher than that in the slow and fast conditions (moderate-slow: p < .001; moderate-fast: p < .001), and there was no significant difference between the slow and fast conditions in this regard (p = .077). CONCLUSION: These results suggest that original tempo BGM led to higher food intake compared to the faster and slower tempo conditions. These findings suggest that listening to music at an original tempo during meals may support appropriate eating behavior.

The effect of an image of watchful eyes on the evaluation of the appearance of food.

It is known that an eye-like image promotes generosity. It is also known that the evaluation of the visual deliciousness of food is improved in the presence of an emotionally positive stimulus. The purpose of the present study was to examine whether the presence of open eyes (OPEN) causes generous behavior altering the evaluation of the visual deliciousness of food, and how the images of open and closed eyes (CLOSED) affect human emotions. Seventeen women participated in the present study. A picture of food was presented on a computer screen, and the participants predicted and evaluated its visual deliciousness. An image of OPEN or that of CLOSED was presented simultaneously with a picture of food. There was a significant difference between the OPEN and CLOSED conditions, as demonstrated by the scores on a nine-point Likert scale for visual deliciousness; the ratings in the OPEN condition were significantly higher than those in the CLOSED condition (p = 0.004). There was no significant difference in the image of watchful eyes for the perceived relaxation state; the ratings in the OPEN condition were not significantly higher than those in the CLOSED condition (p = 0.716). The results of the present study revealed that the evaluation of the visual deliciousness of food based on its appearance was likely due to the presence of an image of open watchful eyes, increasing the perceived visual deliciousness of the food without any changes in the participants' emotions.

Mastication of Hard Gumi Decreases the Gustatory Threshold for Sodium Chloride.

In recent years, there has been an increase in the number of hypertensive diseases and the various diseases associated with them. A major cause of these is excessive salt intake. The purpose of the present study was to examine whether chewing hard foods lowers the saltiness threshold. Fifteen subjects (fourteen women and one man) participated in the present study. Two types of gummies are available as ingredients: hard and soft gummies. The saltiness thresholds before and after chewing of each gummi were studied using 11 different NaCl solutions. Then, points of subjective equality (PSEs) were calculated to detect changes in the saltiness for each subject. In the soft Gumi condition, there was no significant difference in PSE for the saltiness between before and after ingesting Gumi (p>0.05), while in the hard Gumi condition, the PSE for the saltiness significantly decreased after ingesting Gumi compared with the value of before ingesting Gumi (p=0.001). From these results, we concluded that sensitivity to saltiness would increase after mastication of hard foods such as hard Gumi.