We examined the effects of the phantom snacking experience and mastication behavior on human emotions using a compact electroencephalography (EEG) and a KANSEI analyzer. Forty participants were divided into young adult and middle-aged groups. All participants experienced both mastication and phantom snacking. We extracted the emotional parameters from the EEG. There were no significant differences in the levels of alertness, concentration, liking, and stress between the mastication and phantom snacking experiences of younger adults. In the middle-aged group, the interest level was significantly higher, the alertness level was significantly lower, and the stress level tended to be lower in the phantom snacking group than in the mastication group. The interest level tended to be higher, the alertness, and stress levels were significantly lower in the middle-aged phantom snacking group when compared to the younger adult phantom snacking group. Our findings reveal that phantom snacking, similar to mastication, can have a positive effect on the emotions of young adults, and the effects of phantom snacking were better than those of mastication in the middle-aged individuals. Phantom snacking may be a practical method to increase interest, improve work efficiency, and decrease psychological stress.
Mastication behavior is important for food intake and nutrient digestion aided by the teeth. Mastication is a practical behavior that plays an important role in preserving and promoting general physical and mental health [1]. Mastication behavior can improve task performance [2, 3], and is suggested to enhance neuronal activities in various regions of the human brain [4, 5]. Mastication behavior also increases arousal levels and affects motor control. These effects may lead to consequent improvements in cognitive performance. Mastication behaviors can influence human emotions, alleviate psychological stress, improve concentration, and elevate alertness, consequently leading to improvements in mental health.
Phantom Snack is a novel mastication experience system that simulates the experience of eating a snack without actual consumption by employing the visual, auditory, and olfactory senses accompanied by the physical sensation of chewing without actual consumption [6]. Phantom snacks could be useful for various applications, such as helping people reduce their calorie intake, aiding those with dietary restrictions, and providing an entertaining and unique sensory experience. This demonstrates how technology can create a convincing simulation of eating, engaging multiple senses to trick the brain into believing that one is consuming food. It is unclear whether the Phantom Snack experience affects human emotions. This study aimed to investigate the effects of a phantom snack experience on human emotions, compared with the impacts of mastication behavior, using the newly developed KANSEI analyzer.
There are several subjective and objective indices for evaluating human emotions, such as behavioral taxonomy and subjective indices. A more reliable quantitative evaluation would enable an objective and engineered approach. Previous neuroimaging studies with functional magnetic resonance imaging (fMRI) found several brain structures involved in perception, valuation, and regulation of human emotions [7]. An electroencephalogram is a biosignal that acts as an objective index for determining human emotions. It is an electrical signal generated by the activity of the cerebral cortex that allows for a more flexible and noninvasive determination of human brain activity with higher spatial and temporal resolution. Conventional electroencephalography (EEG) is performed using multiple electrodes, but these materials cannot be used in natural environments. This study used a recently developed band-type EEG device (Dentsu ScienceJAM Ltd., Tokyo, Japan) and the KANSEI analyzer, which was recently confirmed and validated for clinical application [8–11]. This system was developed to measure five components of human emotions and mental states from EEG data based on a proprietary algorithm: alertness, concentration, interest, liking, and stress [12].
In this study, we quantitatively evaluated the human emotions of a phantom snacking experience in real time by using a compact EEG device equipped with a KANSEI analyzer. We hypothesized that there would be differences in the age-related changes in human emotions induced by the phantom snacking experience because previous studies have shown that the effect of mastication behavior on brain activity is age-dependent [4, 13, 14].
This study protocol was reviewed and approved by the Ethics Committee of the Institutional Review Board of Dentsu Group Inc., Tokyo, Japan (retrieved on May 29, 2024; registration number: 2024004). All study procedures were conducted in accordance with the institutional and national ethical standards for human experimentation and the Declaration of Helsinki, as revised in 2013. Written informed consent was obtained from all participants.
Study participants
Healthy adults were recruited from a wide range of people at Dentsu Group, Inc. This prospective study included 43 participants. Three participants were excluded because their actual ages were unknown. The remaining 40 participants were divided into young adult and middle-aged groups. The young adult group comprised 18 participants (9 males, 9 females; average age: 30.5±5.3 years, age range 20–39 years). The middle-aged group comprised 22 participants (10 males, 12 females; average age: 49.1±5.0 years, age range 41–56 years). All participants experienced both mastication and phantom snacking. We compared the effects of mastication and phantom snacking between the two groups.
The timeline of the experience is shown in Figure 1. All participants were randomly moved through the sequence of Room 1, Room 2, and Room 3, or through Room 1, Room 3, and Room 2. All experiments were carried out at a temperature of 25°C, humidity of 50%, with illumination below 1,000 lux.
EEG: electroencephalography.
Phantom snacking experience and electroencephalogram-KANSEI analyzer
The outline of the phantom snacking experience is as follows.
1. Visual simulation: The display showed an image of a cookie that gradually decreased in size as the participants mimicked mastication movements (Figure 2). This visual feedback enhanced the illusion of snack consumption.
2. Jaw movement tracking: This system used a web-camera to monitor the participant’s face and estimate the jaw joint movements. These movements were analyzed in real time to synchronize the visual and auditory feedback.
3. Auditory and physical feedback: Bone conduction headphones (ES-BC900, Elesound Electronics Technology Co. Ltd., Dongguan, Guangdong, China) delivered the sound and subtle vibrations of mastication. This added a layer of realism by mimicking the crunching sound and the sensation of chewing.
4. Olfactory stimulation: This system incorporated aromatic oils. By opening a bottle of oil, the participants could smell the cookies, enhance their sensory experience, and make the illusion even more convincing.
The simple, compact EEG device, together with a KANSEI analyzer (Dentsu ScienceJAM Inc., Tokyo, Japan), is a wireless, one-channel system. This device evaluated EEG activity at Fp1 (the left frontal lobe) of the international 10–20 system, applying a frequency of 250 Hz. Thus, the proposed EEG device was confirmed to be suitable for estimating human emotions. The evaluations included reference recordings. An exploring electrode was located at Fp1, and a reference electrode was located at the left ear lobe (Figure 3). EEG data were evaluated every second with the aid of fast Fourier transform. The dispersed signals were acquired, and the EEG data were estimated in real time at 24 Hz and 1 Hz intervals. We applied a band filter between 4 and 22 Hz to remove artifacts such as eye blinking and muscle movements from the EEG data for analysis. The filtered data were then transformed into power spectral features. Using pattern recognition techniques, the emotional parameters were defined and quantitatively analyzed from the obtained EEG database [12].
The KANSEI analyzer is a wireless, one-channel electroencephalogram with one Fp1 electrode (A) and a reference ear electrode (B). The simultaneous use of headphones and electroencephalography (EEG) electrodes (C).
Statistical Analysis
All experimental data are presented as mean ± standard deviation (SD). Statistical analyses were performed using SPSS statistical software (version 22 for Windows, SPSS Inc., Chicago, IL, USA). Statistical analyses were performed using Student’s t-test and two-way analysis of variance followed by Bonferroni’s post hoc multiple comparison tests. Differences were considered statistically significant at P < 0.05.
We evaluated the recorded amplitudes of the components extracted from the EEG for alertness, concentration, interest, liking, and stress during mastication behavior and phantom snacking experience. Representative brainwaves indicating the extracted components of alertness, concentration, interest, liking, and stress are shown in Figure 4.
Regarding the total participants, the average level of interest tended to be higher in the phantom snacking experience group than that in the mastication behavior group (P=0.06). There were no significant differences in alertness, concentration, liking, or stress between the mastication behavior and phantom snacking experience groups (Figure 5).
In the younger adult group, no significant differences were observed between the mastication behavior and phantom snacking experience groups (Figure 6). In the middle-aged group, the average level of interest was significantly higher in the phantom snacking experience group than in the mastication behavior group (P=0.003). The average level of alertness in the phantom snacking experience group was significantly lower than that in the mastication behavior group (P=0.03). The average stress level in the phantom snacking group tended to be lower than that in the mastication behavior group (P=0.08; Figure 6).
Compared to the younger adult phantom snacking experience group, the average level of interest tended to be higher (P=0.07), the average level of alertness (P=0.03), and the stress was significantly lower (P=0.003) in the middle-aged phantom snacking experience group. We did not observe any significant age-related differences in the average level of concentration and liking between the mastication behavior and phantom snacking experience groups (Figure 6).
*P <0.05, **P <0.01.
The main results of this study revealed that the phantom snacking experience affects human emotions. The element of interest was significantly higher, and the element of alertness was significantly lower in the phantom snacking experience group than in the mastication behavior group in the middle-aged cohort. The element of interest tended to be higher, and the elements of alertness and stress were significantly lower in the phantom snacking experience of the middle-aged group compared with the younger adult group.
Interest is defined as trait-like preferences for activities, backgrounds in which activities occur, and outcomes related to favorite activities that initiate goal-oriented behaviors and orient individuals toward specific environments. It is important to understand the nature and role of interest in human behavior and their consequences. The power of interest to predict educational and occupational choices, performance, and success suggest that interest predicts important life outcomes [15]. In this study, we found that interest levels among middle-aged adults were significantly higher in the phantom snacking group than in the mastication group. We believe that the phantom snacking experience may enhance the level of interest of middle-aged individuals.
Lower or higher levels of alertness characteristically result in a leftward or rightward bias in attention. The relationship between alertness and spatial attention may have a major impact on safety and health [16]. Alertness level is also a determinant of work efficiency. In the present study, we found that the alertness level in the middle-aged phantom snacking experience group was significantly lower than in the mastication behavior group. Spatial attention and work efficiency might increase after the phantom snacking experience in middle-aged individuals.
Stress is a state of mental tension or worry under abnormal pressure, which comes from different aspects such as increased workload, deterioration of interpersonal relationships, or financial worries. Stress, which affects both physical and emotional aspects, is a risk factor for numerous disorders, including mental health problems, cardiovascular disease, and other health problems [17, 18]. It is important to effectively manage stress and maintain healthy physical and mental states, protecting our bodies and minds from damage caused by long-term stress. Previous studies have indicated that mastication can ameliorate various stress-induced disorders such as osteoporosis, cancers, and cognitive deficits in experimental animals [19–22]. This study showed that stress levels significantly decreased in the middle-aged phantom snacking experience group. We believe that the phantom snacking experience may serve as a stress management method.
This study had several limitations. First, we compared the emotions between mastication behavior and the phantom snacking experience of young and middle-aged adults. We did not analyze the effects on elderly individuals. If we had more cases involving older individuals, we may obtain more satisfactory conclusions regarding the effects of age. Second, we only recorded EEG signals during mastication behavior and the phantom snacking experience after calibration to obtain more reliable EEG data; control EEG data under a resting condition without snacking were not recorded. Including a control group would strengthen the causal association between snacking and emotions. Nonetheless, this study offers insight into the effects of the phantom snacking experience and mastication behavior, which could positively affect human emotions in young adults. The effects of the phantom snacking experience were more noticeable than those of mastication behavior in middle-aged individuals. We believe that the phantom snacking experience may be a practical method for increasing interest, improving work efficiency, and decreasing psychological stress.
We thank Editage (www.editage.com) for editing the English language of this manuscript.
Ko Izumi and Ryonosuke Ono were involved in the development of the Phantom Snacking system. All other authors declare no conflicts of interest in association with the present study.
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.
