Perceptual and cognitive determinants of tactile disgust

Stevenson R. Differential involvement of the senses in disgust memories

One prediction derived from the disease avoidance account of disgust is that proximal disgust cues (smells, tastes and touches) should elicit this emotion more intensely than distal disgust cues (sights and sounds). If correct, then memories of disgusting experiences should involve smelling, tasting or touching to a greater degree than seeing or hearing. Two surveys were conducted on university students to test this idea, drawing upon their naturalistic experiences. Survey 1 (N = 127) asked participants to detail their most memorable disgusting, fear-provoking, morally repulsive and yucky/gross experience, with each recollection self-rated for sensory involvement. Survey 2 (N = 89) employed the same task, but this time, participants recollected their most common disgusting, fear-provoking, morally repulsive and yucky/gross experience in the preceding week. The majority of disgusting experiences were core disgusts-i.e. related to disease/pathogen presence or stimuli. The proximal and distal sensory cues contributed equally to individuals' most memorable core disgust experiences, but the proximal senses were more involved than the distal senses in individuals' most common core disgust experiences. Further, the proximal sensory cues, as compared with the distal sensory cues, were signficantly more involved in core disgust experiences than in morally repulsive and fear-provoking experiences. The implications of these findings for a disease avoidance account of disgust, for multi-sensory disgust research, and core disgust's classification as an emotion or a drive, are discussed.

Contact forces and motion behavior of non-Newtonian fluid-solid food by coupled SPH-FEM method

The non-Newtonian fluid-solid interaction food has complex physical properties and complicated contact force, which brings the greater technical challenge to improving the food fetching rate. In this work, we used the smooth particle hydrodynamics and finite element coupling method for a node-to-surface penalty function contact to characterize the contact forces between non-Newtonian fluid food and solid foods. The shear rheological properties and density of non-Newtonian fluid food, including xanthan gum (XG) and guar gum (GG), were investigated by a viscometer and densitometer, respectively. The results showed that the shear viscosity of non-Newtonian fluid food depends to some extent on the mass ratio of the thickening gums. We investigated the effects of the end-effector with different fetching velocities and different inclination angles, and the nut root powder paste (NRPP) food with different ratios of XG and GG, on the fetching rate, stress-strain, and motion behavior. The results showed that the stress increased with increasing v₁ and w; however, the v₂ had less effect on the stress. The sparseness of the distribution of solid food was related to the v₁ and w, whereas it was less influenced by the v₂ . The distribution of solid food became denser in the X-Z plane and sparser in the X-Y plane with increasing inclination angle. The motion behavior of viscoelastic solid foods depended on the mass ratio of XG to GG dissolved in NRPP. The present work can provide a theoretical foundation for meal-assisting robots and robots in the field of food engineering with the task of improving the food fetching rate.

Longitudinal changes in disgust sensitivity during pregnancy and the early postpartum period, and the role of recent health problems

Disgust is an essential part of the behavioral immune system, protecting the individual from infection. According to the Compensatory Prophylaxis Hypothesis (CPH), disgust sensitivity increases in times of immunosuppression, potentially including pregnancy. We aimed to replicate a previous study observing longitudinal changes in disgust sensitivity in pregnant women. Additionally, for the first time, we explored how recent health problems influence these changes. To do this, we obtained disgust sensitivity measures from 94 women in each trimester and in early postpartum. In contrast to the original study, where disgust sensitivity was highest in the first trimester, we found that overall and animal reminder disgust increased across pregnancy and after birth. In line with the CPH, women who were recently sick in the first trimester had elevated disgust sensitivity at that time. Although disgust sensitivity was significantly higher in the second trimester and postpartum period compared to the first trimester in mothers pregnant with a male fetus, the overall results regarding the effect of fetus sex on disgust sensitivity were mixed. It seems that changing levels of disgust sensitivity during pregnancy and postpartum result from a suite of physiological and psychological changes that occur during this sensitive period of a woman's life.

What's in a name? Role of verbal context in touch

Can a name (i.e. verbal context) change how we react to and perceive an object? This question has been addressed several times for chemosensory objects, but appears unanswered for touch. To address this, two studies were run. In each, we allocated participants to a Positive, Neutral or Negative Group, and asked them to touch the same four objects, twice-first, named by the experimenter according to their Group-name, and second, named by the participant. Participants were timed as they touched and rated the objects on pleasantness and disgust. Negative-named objects were touched for shorter durations, and rated more negatively, than neutral-named objects, and positive-named objects were touched for the longest and rated most positively. In the second presentation, most objects (greater than 90%) were named by participants in accordance with their assigned Group-names. The similarity of these findings to chemosensory verbal context effects and their mechanistic basis is discussed.

Effects of sickness manipulation on disgust and pleasantness in interpersonal touch

The theory of the behavioral immune system (BIS) describes a set of behaviors that protect the individual from infectious diseases and that are motivated by disgust and the perceived vulnerability to disease. As interpersonal touch is one of the most common situations of potential transmission of infectious diseases in our everyday life, it seems likely that being touched by an apparently sick individual activates disgust. Our aim was to determine if risk of contamination from interpersonal touch alters the pleasantness of interpersonal touch and modulates facially expressed emotions. In total, 64 participants received interpersonal stroking by either a healthy or by sick-appearing experimenter. Half the strokes were performed at a slow velocity of 3 cm/s and half at a faster velocity of 30 cm/s, to modulate the degree of C-tactile fiber activation in the touch perceiver. While the experimental sickness manipulation did not influence the reported touch pleasantness, there was a tendency for a diminished expression of happiness in the slow stroking condition. In addition, the desire to clean the arm after stroking correlated positively to disgust sensitivity and to germ aversion, which is a subscale of the perceived vulnerability to disease. Contrary to previous studies, participants did not prefer the slow over the fast stroking velocity, irrespective of sickness induction. Our results lead us to assume that disgust in interpersonal touch depends especially on the touch receiver and we speculate that a rather conservative reactivity of the BIS allows for an adaptive behavioral balance in interpersonal relations. This balance may be needed to weight the risks of contamination against the benefits of interpersonal touch for social interaction.

Food neophobia and the evaluation of novel foods in adults; the sensory, emotional, association (SEA) model of the decision to taste a novel food

Reluctance to eat new foods, known as food neophobia, is well researched in children but not adults. Two studies were carried out to understand the emotional, sensory, and cognitive factors associated with food neophobia in an adult sample, and to propose a preliminary explanation of the decision to taste a novel food named the SEA model (Sensory, Emotional, cognitive Association model). Participants were recruited through opportunity sampling of a university population in the Leicester region of the UK. Study one (n = 534) was a cross sectional study examining associations between self-report measures of food neophobia, emotional variables and sensory variables. In study two (n = 160), participants completed an online cognitive evaluation of 7 images of novel fruits and vegetables, rating perceived familiarity, categorisation as fruit or vegetable, cognitive associations based on appearance (what does the food look like), liking of any associated foods, and expected liking of the novel food. In study 1 it was found that tactile sensitivity and disgust sensitivity were the main sensory and emotional variables associated with food neophobia. In study 2, it was found that food neophobia and lower expected liking of novel foods were associated with disgust sensitivity, associating the novel foods with disliked foods, and lower perceived familiarity. The SEA model further proposes that underlying tendencies and automatic reactions to foods, combine with cognitive associations based on negative memories and negative beliefs about tasting new foods, to create expected disliking of a food and a decreased likelihood that it will be tried. Further work is needed to fully test the SEA model of the decision to taste a novel food, in particular to further examine how associations are formed.

Tactile disgust: Post-contact can be more disgusting than contact

Several studies have examined if disgust can be evoked by contacting an object-yet none have examined if reported disgust changes when the hand leaves the object. This is surprising given that post-contact tactile disgust is probably a driver of hand hygiene. We examined contact and post-contact tactile disgust and its sensory origins. Participants were asked to touch several objects, making sensory, disgust, and desire-to-handwash evaluations. These ratings were made at three stages-of-contact: object-contact (just touch), post-contact (just touch), and visual post-contact (touch, vision). Disgust was typically highest at post-contact (when the hand left the object). Stickiness and wetness were uniquely predictive of object-contact disgust. Only stickiness drove post-contact disgust, and only wetness visual post-contact disgust. Hand-washing desire was primarily driven by quantity of residue perceived on the hand. These findings suggest that tactile disgust is a multisensory and iterative process relating to object- and residue-adhesiveness.

Conducting exposure and response prevention treatment for contamination fears during COVID-19: The behavioral immune system impact on clinician approaches to treatment

The coronavirus disease 2019 (COVID-19) pandemic sparked significant anxiety regarding viral rates and means of transmission. Heightened concerns about contamination have prompted new hygienic strategies to vigilantly guard against infection, including hand washing immediately after touching foreign objects or suspected contaminants. This has presented a critical challenge for the delivery of exposure and response prevention (ERP) therapy to individuals with contamination fears due to Obsessive Compulsive Disorder (OCD), as providers must manage not only their clients' attitudes and reactions but their own as well. In this investigation, self-identified anxiety and OCD treatment specialists (N = 139) provided demographic information, including their anxiety and OCD caseloads, and completed measures related to intolerance of uncertainty (IUS-SF; Carlton et al., 2007), beliefs about exposure therapy (TBES; Deacon et al., 2013), and emotional reactions to physical sensations (The Chills; Maruskin et al., 2012). We tested the hypothesis that intolerance of uncertainty and activation of the behavioral immune system (BIS; Schaller & Park, 2011), a mechanism theoretically activated by the prominent emergence of pathogens to protect against illness would predict attitudes toward exposure. The Chills Scale was used to assess BIS activation, a broad assessment of vasoconstriction responses associated with different emotional reactions, and includes a subscale (coldness) that evaluates vasoconstriction associated with defense against pathogens. Both coldness and OCD caseload, but not anxiety caseload or subscales of intolerance of uncertainty, emerged as significant predictors of clinicians' beliefs about exposure; increases in OCD caseload were also related to decreases in negative beliefs about exposure. Findings are useful in determining methods for aiding clinicians in developing effective approaches to contamination fears during and post-pandemic that include addressing their own BIS-related concerns and mapping out means for social behavioral norms associated with engaging in exposure treatment.

Aversive textures and their role in food rejection

Texture is a prominent feature in foods and consequently can be the reason a food is accepted or rejected. However, other sensory attributes, such as flavor/taste, aroma, sound, and appearance may also lead to the rejection of food and motivations other than unpleasantness exist in unacceptance. To date, these motivations for food rejection have been studied in isolation and their relationships with psychological factors have not been tested. This study measured reasons people reject a food and probed into the specifics of texture rejection. A large U.S. sample (N = 473) was asked to rate their motivations for rejecting a food, list foods that were disliked due to unpleasant sensory attributes, specify the unpleasant sensory attribute(s), and complete an assessment of general touch sensitivity. Results showed 94% of individuals reject a food due to its texture, a rate comparable to flavor-based rejection. Looking at the number of foods being rejected, flavor was the most common food attribute, followed by texture and then aroma. From a linguistic standpoint, aversive textures encompass a large vocabulary, larger than liked textures, and the same food may be rejected due to a single or combination of texture terms. Viscosity (e.g., slimy) and hardness (e.g., mushy) are the most common aversive texture types, but through cluster analysis subsets of individuals were identified that are more aversive to other textures. This study emphasizes the role of aversive textures in food rejection and provides many avenues for future investigations.

It's not you, it's me - disgust sensitivity towards body odor in deaf and blind individuals

Disgust might be elicited by various sensory channels, including the sense of smell. It has been previously demonstrated that unpleasant odors emitted by an external source are more disgusting than those emitted by oneself (the source effect). As disgust's main purpose is to help organisms avoid potentially dangerous, contaminating objects, individuals with visual or hearing sensory impairment (thus, with an impeded ability to detect cues indicating pathogen threat) might have developed an increased levels of olfactory disgust sensitivity (modality compensation in disgust sensitivity). We set out to investigate disgust sensitivity in olfaction using the Body Odor Disgust Scale (BODS) on a large sample of 74 deaf and 98 blind participants, with comparison to control groups without sensory impairment (N = 199 in total). The results did not support the hypothesis of modality compensation in disgust sensitivity. Contrary to previous research, neither sex nor age influenced the outcomes. Evidence for the source effect was found. Acquired data are interpreted in the light of social desirability. The emphasis put on the olfaction by blind and deaf individuals is discussed.