Making your skin crawl: The role of tactile sensitivity in disease avoidance

Validating the Revised Mating Effort Questionnaire

The mating effort questionnaire (MEQ) is a multi-dimensional self-report instrument that captures factors reflecting individual effort in upgrading from a current partner, investment in a current partner, and mate seeking when not romantically paired. In the current studies, we sought to revise the MEQ so that it distinguishes among two facets of mate seeking-mate locating and mate attracting-to enable a more nuanced measurement and understanding of individual mating effort. Moreover, we developed additional items to better measure partner investment. In total, the number of items was increased from 12 to 26. In Study 1, exploratory factor analysis revealed that a four-factor solution, reflecting partner upgrading, mate locating, mate attracting, and partner investment, yielded the best fit. In Study 2, this structure was replicated using confirmatory factor analysis in an independent sample. Based on extant studies documenting the relationships between psychopathy, short-term mating effort, and sexual risk taking, a structural equation model (SEM) indicated that trait psychopathy positively predicted mate locating, mate attracting, and partner upgrading and negatively predicted partner investment. A separate SEM showed that partner upgrading positively predicted risky sexual behaviors, while partner upgrading and mate locating positively predicted acceptance of cosmetic surgery.

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.

The skin crawls, the stomach turns: ectoparasites and pathogens elicit distinct defensive responses in humans

Disgust has long been viewed as a primary motivator of defensive responses to threats posed by both microscopic pathogens and macroscopic ectoparasites. Although disgust can defend effectively against pathogens encountered through ingestion or incidental contact, it offers limited protection against ectoparasites, which actively pursue a host and attach to its surface. Humans might, therefore, possess a distinct ectoparasite defence system-including cutaneous sensory mechanisms and grooming behaviours-functionally suited to guard the body's surface. In two US studies and one in China, participants (N = 1079) viewed a range of ectoparasite- and pathogen-relevant video stimuli and reported their feelings, physiological sensations, and behavioural motivations. Participants reported more surface-guarding responses towards ectoparasite stimuli than towards pathogen stimuli, and more ingestion/contamination-reduction responses towards pathogen stimuli than towards ectoparasite stimuli. Like other species, humans appear to possess evolved psychobehavioural ectoparasite defence mechanisms that are distinct from pathogen defence mechanisms.

Disease Avoidance Model Explains the Acceptance of Cohabitation With Bats During the COVID-19 Pandemic

Bats and humans have a close relationship based on cohabitation, with bats taking roost in buildings. It has been suggested that bats function as a reservoir of the SARS-CoV-2 virus that causes the COVID-19 disease in humans. A misconception that bats can spread SARS-CoV-2 to humans may have increased negative emotions toward bats and reduced individuals' acceptance of cohabitation with bats during the COVID-19 pandemic. By applying the disease avoidance model, we tested whether knowledge about bats would be associated with reduced negative emotions toward bats, which in turn would be associated with increased acceptance of cohabitation with bats. Moreover, we tested whether previous experiences of bats, perceived COVID-19 risk, age, gender and level of education would be associated with negative emotions and acceptance of bats. A quantitative survey (N = 577) collected during the COVID-19 pandemic in Finland was analyzed with multiple linear regression. The results supported the disease avoidance model. Negative emotions toward bats reduced the acceptance of cohabitation with bats. However, knowledge about bats was associated with increased acceptance of bats both directly, as well as indirectly, via reduced negative emotions. Moreover, perceived COVID-19 risk was associated with increased negative emotions toward bats, and reduced acceptance of bats. Females were more likely than other respondents to report negative emotions, and reduced acceptance of cohabitation with bats. Prior experience of bats was associated with increased acceptance of bats as neighbors. These findings suggest that COVID-19 pandemic may threaten the existence of bats if no action is taken. The findings highlight the importance of correcting misunderstandings about non-human species as transmitters of diseases to humans.

Desire to eat and intake of 'insect' containing food is increased by a written passage: The potential role of familiarity in the amelioration of novel food disgust

Over two studies we investigated the effect of various written interventions (passages) on the disgust response towards a food (falafels) which supposedly contained mealworm (insect) flour. Actually, participants (Study 1 N = 80, Study 2 N = 78) were given the same non-mealworm containing food in all conditions. Disgust was measured using: tactile sensitivity, food intake, liking and desire to eat. Results of Study 1 showed that a sustainability passage (sustainability advantages of entomophagy), but not a delicacy passage (oro-sensory qualities of insects), was effective in reducing disgust. In Study 2, contrary to prediction, a passage describing the sustainability and nutritional advantages entomophagy failed to reduce disgust - falafel intake, liking and desire to eat were decreased. However, a passage which described how mealworm flour is produced, did significantly reduce disgust. Taken together, these studies demonstrate that written passages can alter the disgust response, notably resulting in a maintenance of food intake. Interventions that increase the perception of familiarity of a novel food, but not logic-based arguments, may be a key driver of the amelioration of disgust. These results also support the suggestion that altering the ideational component of disgust can result in changes of distaste perception.

What people believe about detecting infectious disease using the senses

Do you believe you can tell if people are sick with infectious diseases by looking at, listening to, or smelling them? Research on pathogen detection and avoidance suggests that perceivers respond with caution both to true signs of infection and to cues only heuristically associated with infection threat. But what do perceivers actually believe about the effectiveness and use of specific sensory modalities for infection detection? In several studies, U.S. participants reported perceptions of effectiveness and likelihood of using each of the major senses to identify infection threat in two types of targets: people and food. Results revealed prioritization of sight and sound with person targets and prioritization of sight and smell with food targets. These patterns appear consistent with the use of "safe senses" (avoidance of cues involving high perceived transmission risk). Beliefs about sensory use also varied depending on the specific feature being examined, with different patterns of sensory beliefs associated with evaluation of pathogenic danger than with evaluation of desirability and fit with normative standards. We discuss these lay beliefs in the context of recent calls for descriptive research in psychology as well as their implications for current and future work on the behavioral immune system.

Sounds of sickness: can people identify infectious disease using sounds of coughs and sneezes?

Cough, cough. Is that person sick, or do they just have a throat tickle? A growing body of research suggests pathogen threats shape key aspects of human sociality. However, less research has investigated specific processes involved in pathogen threat detection. Here, we examine whether perceivers can accurately detect pathogen threats using an understudied sensory modality-sound. Participants in four studies judged whether cough and sneeze sounds were produced by people infected with a communicable disease or not. We found no evidence that participants could accurately identify the origins of these sounds. Instead, the more disgusting they perceived a sound to be, the more likely they were to judge that it came from an infected person (regardless of whether it did). Thus, unlike research indicating perceivers can accurately diagnose infection using other sensory modalities (e.g. sight, smell), we find people overperceive pathogen threat in subjectively disgusting sounds.

Exploring the Role of the Behavioral Immune System in Acceptability of Entomophagy Using Semantic Associations and Food-Related Attitudes

Entomophagy refers to eating insects. Insect food, including cooked insects and other processed food with insect-based ingredients, is consumed in many regions of the world as a part of traditional dietary behavior, or as innovative functional food. However, many people especially in western or industrialized societies have shown negative attitudes such as resistance or disgust to entomophagy. In this study, we examined the acceptability of eating insects from the context of the behavioral immune system (BIS), by employing a questionnaire survey and picture-based semantic association experiment. We collected data from 1,369 Japanese participants (581 females and 788 males, mean age = 43.41 years, SD = 10.44 years) by conducting an online survey. The results revealed the influence of the behavioral immune system on entomophagy: The semantic associations between insect food and non-insect food, and between insect food and pathogens were significantly predicted by multiple domains related to the attitudes, concerns, and experience of food and pathogens. The semantic associations between insect food and pathogens were significantly stronger than other associations. People who concentrate on food safety and hygiene revealed fewer associations between insect food and non-insect food. These results indicated that promoting the sanitary and hygienic image of insect food may reduce revulsion at entomophagy and promote uptake.

Visual Perception of Moisture Is a Pathogen Detection Mechanism of the Behavioral Immune System

The behavioral immune system (BIS) includes perceptual mechanisms for detecting cues of contamination. Former studies have indicated that moisture has a disgusting property. Therefore, moisture could be a target for detecting contamination cues by the BIS. We conducted two experiments to examine the psychophysical basis of moisture perception and clarify the relationship between the perception of moisture and the BIS. We assumed that the number of high luminance areas in a visual image provided optical information that would enable the visual perception of moisture. In two experiments, we presented eight images of dough that contained different amounts of moisture as experimental stimuli. The amount of moisture shown in the images was increased in eight steps, from 28.6 to 42.9% of the total weight of the dough. In Experiment 1, the images were randomly presented on a computer display, and the participants (n = 22) were asked to rank the images in the order of the visually perceived moisture content. In Experiment 2, the participants (n = 15) completed pairwise comparisons based on the perceived moistness of the images. Furthermore, to examine the BIS responses, the participants rated the strength of disgust evoked by the stimuli, their motivation to avoid touching the stimuli, and the estimated magnitude of the risk of contamination by physical contact with the stimuli. The results indicated that the moisture content and the numbers of high luminance areas in the images accurately predicted the perception of moisture, suggesting that the detection of visual moisture was highly accurate, and the optical information served as an essential perceptual cue for detecting moisture. On the other hand, the BIS responses peaked in response to stimuli having approximately 33 to 39% moisture content. These results show that objects containing a moderate amount of moisture could be the target of visually detecting pathogens by the BIS.

Perceptual and cognitive determinants of tactile disgust

Tactile cues are said to be potent elicitors of disgust and reliable markers of disease. Despite this, no previous study had explored what the full range of tactile properties are that cue disgust, nor how interpretation of these sensations influences disgust. To answer these questions, participants were asked to touch nine objects, selected to cover the range of tactile properties, and evaluate their sensory, affective, and risk-based characteristics (primarily how sick they thought the object would make them). Object contact was manipulated in four ways, with participants randomly allocated to corresponding groups-one that could see the objects (i.e., the control) and three that could not (i.e., the blind groups). To manipulate disease risk interpretation of the objects, labelling was used on the blind groups, with one receiving Disgust-Labels, one True-Labels and one no labels. Disgust was strongly associated with sticky and wet textures, and moderately with viscous, cold, and lumpy textures, suggesting adherence-to-skin may predict disgust. The participants in the disgust-labelled condition had the highest disgust ratings, and this was mediated by their increased sickness belief and fear of the objects. Object identification was poor when labels or visual cues were absent. Our findings suggest that tactile disgust may reflect a bottom-up sensory component-skin adhesion-moderated by judgements of disease-related threat.

Ectoparasite defence in humans: relationships to pathogen avoidance and clinical implications

Currently, disgust is regarded as the main adaptation for defence against pathogens and parasites in humans. Disgust's motivational and behavioural features, including withdrawal, nausea, appetite suppression and the urge to vomit, defend effectively against ingesting or touching sources of pathogens. However, ectoparasites do not attack their hosts via ingestion, but rather actively attach themselves to the body surface. Accordingly, by itself, disgust offers limited defence against ectoparasites. We propose that, like non-human animals, humans have a distinct ectoparasite defence system that includes cutaneous sensory mechanisms, itch-generation mechanisms and grooming behaviours. The existence of adaptations for ectoparasite defence is supported by abundant evidence from non-human animals, as well as more recent evidence concerning human responses to ectoparasite cues. Several clinical disorders may be dysfunctions of the ectoparasite defence system, including some that are pathologies of grooming, such as skin picking and trichotillomania, and others, such as delusory parasitosis and trypophobia, which are pathologies of ectoparasite detection. We conclude that future research should explore both distinctions between, and overlap across, ectoparasite defence systems and pathogen avoidance systems, as doing so will not only illuminate proximate motivational systems, including disgust, but may also reveal important clinical and social consequences.This article is part of the Theo Murphy meeting issue 'Evolution of pathogen and parasite avoidance behaviours'.

PsychoBehavioroimmunology: Connecting the Behavioral Immune System to Its Physiological Foundations

Although infectious disease has posed a significant and persistent threat to human survival and welfare throughout history, only recently have the psychological and behavioral implications of disease threat become a topic of research within the behavioral sciences. This growing body of work has revealed a suite of affective and cognitive processes that motivate the avoidance of disease-causing objects and situations—a cascade of processes loosely conceptualized as a “behavioral immune system (BIS).” Recent BIS research has linked disease threat to a surprisingly broad set of psychological and behavioral phenomena. However, research examining how the BIS is nested within our broader physiology is only beginning to emerge. Here, we review research that has begun to elucidate the physiological foundations of the BIS—at the levels of sensory modalities, cells, and genes. We also discuss the future of this work.