Visual attention is not attuned to non-human animal targets' pathogenicity: an evolutionary mismatch perspective

A considerable amount of research has revealed that there exists an evolutionary mismatch between ancestral environments and conditions following the rise of agriculture regarding the contact between humans and animal reservoirs of infectious diseases. Based on this evolutionary mismatch framework, we examined whether visual attention exhibits adaptive attunement toward animal targets' pathogenicity. Consistent with our predictions, faces bearing heuristic infection cues held attention to a greater extent than did animal vectors of zoonotic infectious diseases. Moreover, the results indicated that attention showed a specialized vigilance toward processing facial cues connoting the presence of infectious diseases, whereas it was allocated comparably between animal disease vectors and disease-irrelevant animals. On the other hand, the pathogen salience manipulation employed to amplify the participants' contextual-level anti-pathogen motives did not moderate the selective allocation of attentional resources. The fact that visual attention seems poorly equipped to detect and encode animals' zoonotic transmission risk supports the idea that our evolved disease avoidance mechanisms might have limited effectiveness in combating global outbreaks originating from zoonotic emerging infectious diseases.

It tastes OK, but I don't want to eat it: New insights into food disgust

To better understand food-disgust, we investigated the long-standing theory that disgust towards a food causes it to taste 'bad'. To induce disgust, participants were served cookies labelled as containing crickets (Study 1); or served whole crickets versus novel (leblebi) and familiar (peanuts) control foods (Study 2). Participants (Study 1: N = 80; Study 2: N = 90) tasted the foods and rated taste pleasantness, desire to eat, disgust and, in Study 1, 16 taste attributes (e.g., nuttiness). Latency to eat and food intake were included as behavioural indicators of disgust. In both studies disgusting foods were presumed to taste bad, but this was disconfirmed after tasting - disgust did not cause the food to taste bad. Nonetheless, the taste attribute results suggested increased attention towards cricket flavours/textures. Furthermore, desire to eat and intake results suggested that disgust, but not novelty, was associated with reduced food wanting. Even if a disgust-inducing food tastes OK, people do not 'want' to consume it. By offering novel insights into our understanding of disgust, these results may stimulate progress in new avenues of emotion research, as well as informing the development of methods to reduce disgust and increase the acceptance of novel, sustainable, foods. For example, interventions should encourage tasting to overcome negative expectations of taste pleasantness and should tackle low levels of wanting, e.g., by normalising consumption of the target food.

Functional Heuristics of Disease Transmission from Physical Deformities in Food Preferences

Ostensibly serving to restrict contact with disease vectors, humans exhibit aversion toward cues heuristically inferred as pathogenic. This restriction could lead perceivers to downregulate their interest in food consumption, even if such cues may not connote actual disease threats. This proclivity to avoid disease led us to consider how heuristic disease cues inform interest in foods. Participants evaluated a hypothetical food preparer that varied in the presence of heuristic cues to disease transmission (i.e., physical deformities versus healthy control). Individuals with low levels of perceived infectability were more discerning of the social target as a function of disease cues, whereas heightened levels of this trait fostered an overall aversion to targets regardless of health status. Results provide continued evidence for how pathogen avoidance motives compete with other somatic motives.

Moral emotions and justifying beliefs about meat, fish, dairy and egg consumption: A comparative study of dietary groups

Meat eaters and meat abstainers differ in their beliefs and moral emotions related to meat consumption alongside gender differences. Few studies have investigated beliefs and moral emotions in pescatarians and vegans. Little is known about differences in moral emotions and beliefs regarding dairy, eggs, and fish or about speciesist beliefs within and between specific dietary groups. To address this gap, we investigated moral emotions (consumption-related disgust and guilt), attitudes towards animals (Animal Attitudes Scale) and justifying beliefs related to meat (Carnism Inventory), dairy, egg, and fish consumption in omnivores (n = 167), pescatarians (n = 110), vegetarians (n = 116), and vegans (n = 149). Results showed that people who consumed animal-derived products reported lower disgust and guilt and held stronger justifying beliefs about consumption of these products than those who did not consume animal products. All dietary groups significantly differed from each other in their attitudes about using animals for human benefit, with omnivores showing the least positive attitudes towards animals, followed by pescatarians and vegetarians, and with vegans showing the most positive attitudes towards animals. Women experienced greater moral emotions and held fewer justifying beliefs than men within groups where animal products were consumed and related to the animal-based products they consume (i.e., fish for pescatarians and eggs/dairy for vegetarians). These findings emphasise the importance of considering a wider range of animal products, such as eggs, dairy and fish, and dietary groups in order to obtain a comprehensive understanding of the psychological underpinnings of animal product consumption. The results highlight differences between dietary groups in attitudes and moral concern towards animals, which may be important to consider when designing interventions to reduce animal product consumption.

Disgust as a transdiagnostic index of mental illness: A narrative review of clinical populations

Disgust is a basic emotion of rejection, providing an ancestral defensive mechanism against illness. Based on research that documents altered experiences of disgust across several psychopathological conditions, we conducted a narrative review to address the hypothesis that altered disgust may serve as a transdiagnostic index of mental illness. Our synthesis of the literature from past decades suggests that, compared to healthy populations, patients with mental disorders exhibit abnormal processing of disgust in at least one of the analyzed dimensions. We also outline evidence of alterations in brain areas relevant to disgust processing, such as the insula and the interconnected limbic network. Overall, we provide preliminary support for the hypothesis that altered disgust processing may serve as a transdiagnostic index of mental illness.

The Development of Disgust and Its Relationship to Adolescent Psychosocial Functioning

Experiences of excessive disgust have been implicated in several psychopathologies. Research, however, has rarely examined disgust and its role in psychosocial functioning from a developmental standpoint. This study examines the relationship between disgust expression in early life and subsequent adolescent psychosocial functioning. Data from 165 children were collected as part of a longitudinal study. Disgust propensity in infancy and childhood was assessed using a facial expressivity task and food aversion task, respectively. Adolescent psychosocial functioning was measured through several self-report measures. Results suggest that there exists a degree of consistency in disgust expression within the first year of life, and that childhood disgust propensity may be related to impairment in early adolescent psychosocial functioning. These findings highlight the potential importance of identifying early disgust expression as a marker for later psychopathology.

Decoding Emotion in Drug Abusers: Evidence for Face and Body Emotion Recognition and for Disgust Emotion

Background: Different drugs damage the frontal cortices, particularly the prefrontal areas involved in both emotional and cognitive functions, with a consequence of decoding emotion deficits for people with substance abuse. The present study aimed to explore the cognitive impairments in drug abusers through facial, body and disgust emotion recognition, expanding the investigation of emotions processing, measuring accuracy and response velocity. Methods: We enrolled 13 addicted to cocaine and 12 alcohol patients attending treatment services in Italy, comparing them with 33 matched controls. Facial emotion and body posture recognition tasks, a disgust rating task and the Barrat Impulsivity Scale were included in the experimental assessment. Results: We found that emotional processes are differently influenced by cocaine and alcohol, suggesting that these substances impact diverse cerebral systems. Conclusions: Drug abusers seem to be less accurate on elaboration of facial, body and disgust emotions. Considering that the participants were not cognitively impaired, our data support the hypothesis that emotional impairments emerge independently from the damage of cognitive functions.

The relationship between meat disgust and meat avoidance-A chicken-and-egg problem

Feelings of disgust toward meat have been researched for at least 30 years, but so far the causal relationship that may link meat disgust and meat consumption has remained elusive. Two possible pathways have been proposed in previous literature: the more common pathway seems to be that meat disgust is developed after a transition to vegetarianism, potentially via the process of moralization and recruitment of (moral) disgust. Other accounts suggest the existence of a second pathway in which disgust initiates the avoidance of meat and this can be explained by existing theories of disgust functioning as a pathogen avoidance mechanism and meat serving as a pathogen cue. However, the evidence base for either relationship remains thin and to our knowledge no research has examined whether temporary meat abstention can lead to increases in meat disgust, as the first pathway suggests. We measured meat disgust and meat intake in n = 40 meat eaters before and after attempting a meat-free diet for 1 month (while taking part in the annual vegan campaign Veganuary). Although most participants lapsed to eating meat during this period, we found that reductions in meat intake during the month were predictive of increases in meat disgust afterwards. This supports the view that meat disgust is expressed as a result of meat avoidance in meat eaters. Implications for theoretical understanding of the relationship between meat disgust and meat avoidance, as well as the development of disgust based interventions are discussed.

The relationship between tendency to attend to detail, sensory sensitivity, and affective response to food cues - A registered report

Understanding the underlying drivers of food choice remains a challenge and has highlighted the need for measures that capture data over and above that offered by self-reporting tools. Consequently, a growing body of research has set out to interpret facial responses to food cues to offer a greater insight into the emotional responses that may drive food acceptance. However, interpreting facial responses is challenging, as there are numerous factors that may influence affective response to foods, including expectation, context, and individual differences. Existing findings suggest there is a link between autistic traits and sensory sensitivities; research highlights further links between sensory sensitivities and eating behaviour, and autistic traits and eating behaviour, with a body of research focusing on the autistic trait attention to detail (ATD). As such, the current study aimed to examine rapid facial activity in response to foods cues while capturing these individual differences present in the general population. This study found no evidence to suggest facial responses to food pictures were linked with attention to detail or hyper-sensitivity. The findings did support a general link between self-reported pleasantness ratings of viewed foods and activity of facial muscles. Post-hoc analyses suggested scoring on the social skills sub-scale of the Autism Quotient (AQ) was associated with levator activity while viewing pictures low in pleasantness. This study offers a greater understanding of variations, at the individual level, which are associated with affective response to foods, and may help to inform the development of tools that set out to predict food acceptance.

Meat disgust is negatively associated with meat intake - Evidence from a cross-sectional and longitudinal study

Meat consumption is increasingly seen as unsustainable, unhealthy, and unethical. Understanding what factors help people reduce their meat intake is urgently needed. One such factor is meat disgust, a feeling reported by many vegetarians, and which could be a promising basis for meat reduction interventions. However, meat disgust and its impact on meat consumption is poorly understood. We examined meat disgust and its role in vegetarianism and reducing meat intake in a cross-sectional and longitudinal online study. We measured self-reported meat consumption, meat disgust (by self-report and Implicit Association Test), meat liking, self-control, and disgust sensitivity in N = 711 adults (57% omnivores, 28% flexitarians, 15% vegetarians) recruited from a community cohort. Results showed that 73% of vegetarians can be classified as 'meat disgusted', and that meat disgust predicted meat intake better than self-control in omnivores and flexitarians at baseline. Following up a sub-sample of participants (N = 197) after six months revealed that changes in meat intake over time were also associated with changes in meat disgust. This is the first study to quantify the impact of meat disgust on (changes in) meat consumption and its prevalence in the vegetarian and the general population. Our findings advance research into meat disgust and encourage the development of disgust-based interventions to reduce meat intake.

Neural Coding of Food Is a Multisensory, Sensorimotor Function

This review is a curated discussion of the relationship between the gustatory system and the perception of food beginning at the earliest stage of neural processing. A brief description of the idea of taste qualities and mammalian anatomy of the taste system is presented first, followed by an overview of theories of taste coding. The case is made that food is encoded by the several senses that it stimulates beginning in the brainstem and extending throughout the entire gustatory neuraxis. In addition, the feedback from food-related movements is seamlessly melded with sensory input to create the representation of food objects in the brain.

Facial EMG Activity Is Associated with Hedonic Experiences but not Nutritional Values While Viewing Food Images

The physiological correlates of hedonic/emotional experiences to visual food stimuli are of theoretical and practical interest. Previous psychophysiological studies have shown that facial electromyography (EMG) signals were related to subjective hedonic ratings in response to food images. However, because other data showed positive correlations between hedonic ratings and objective nutritional values of food, whether the facial EMG reactions to food images could reflect the hedonic evaluation or nutritional assessment of food remains unknown. To address this issue, we measured subjective hedonic ratings (liking, wanting, valence, and arousal) and physiological signals (facial EMG of the corrugator supercilii, zygomatic major, masseter, and suprahyoid muscles, skin potential responses, and heart rates) while participants observed food images that had objective nutritional information (caloric, carbohydrate, fat, and protein contents). The results revealed that zygomatic major EMG activity was positively correlated with ratings of liking, wanting, and valence, but not with any objective nutritional value. These data indicate that facial EMG signals in response to food images reflect subjective hedonic experiences, but not objective nutritional values, associated with the food item.

Consumer acceptance of novel food technologies

Novel food technologies are important for food security, safety and sustainability. Consumers, however, are often hesitant to accept them. In this narrative Review, we organize the research describing how heuristics and individual differences among consumers influence the acceptance of agri-food technologies. Associations evoked by a food technology, its perceived naturalness and trust in the industry using it influence consumer acceptance. Food neophobia, disgust sensitivity and cultural values are crucial personality factors for explaining individual differences. Using gene technology, nanotechnology, cultured meat and food irradiation as cases, we explore factors that may explain consumers' acceptance or lack of acceptance. Climate change, food supply shocks caused by crises such as pandemics and population growth are imminent threats to the food system. Therefore, disruptive food technologies will be needed to progress towards a more resilient food system. Taking into account the factors influencing consumers' perceptions of novel food technologies during the early stage of development and introduction will hopefully result in a higher acceptance of such technologies.

Alcohol and disgust: An intimate relationship

BACKGROUND

Alcohol intoxication has been associated with increases in risk taking behavior and more ambiguously, alterations in emotional perception. In the first study of its kind, we examine how theories of disgust can be used to help explain these effects.

METHODS

Using a single-blind procedure, participants (n = 73) were randomly allocated to an alcohol (Males: 0.68 g/kg; Females: 0.60 g/kg) or placebo condition and then completed a psychometric measure of disgust (TDDS).

RESULTS

Results revealed a non-significant trend toward lower disgust sensitivity in the alcohol versus placebo condition. We did however find a significant negative correlation, whereby increases in breath alcohol level were associated with decreased pathogen disgust.

CONCLUSIONS

These findings demonstrate a relationship between breath alcohol level and disgust sensitivity which could help explain differences in risk associated behavior.

An unfamiliar social presence reduces facial disgust responses to food stimuli

Consumers' emotional responses complement sensory and hedonic ratings in the prediction of food choice and consumption behaviour. The challenge with the measurement of consumption emotions is that emotions are highly context dependent. For emotion evaluations to bring greater insight to food research and development, it is essential that the influence of contextual variables on emotion are quantified. The present study contributes to the discussion with an investigation of the effect of an unfamiliar social presence on affective facial responses to visual food stimuli. Seventy participants (52 female and 18 male) viewed food images of varying acceptability either alone, or in the presence of the researcher. Subjective liking ratings were measured using a labelled affective magnitude scale, and facial muscle activity from zygomaticus major (contracted during smiling), corrugator supercilii (contracted during frowning) and levator labii superioris (contracted during nose wrinkling) were measured with an EMG recording system. Controlling for individual differences in facial expressivity and food image acceptability using linear mixed models, it was found that social context did not predict smiling or frowning muscle activity. Social context did predict the intensity of muscle activity indicative of a disgust response, with participants in the observed condition exhibiting less levator activity than participants in the alone condition. Regardless of social context, each muscle was found to have a relationship with subjective liking, with the direction of effects as expected. The results indicate that emotional stimuli and social context both influence food-evoked facial expression and provides support for the utility of facial EMG in measuring food-evoked emotion.

AKT1, PRDM4, and BAX are the natural markers of psychological endurance threshold

INTRODUCTION

Abnormal behavior can cause harm or loss to oneself, the family, and society and may be related to psychological endurance levels. With early identification and early intervention, the occurrence of harm can be prevented and the loss can be reduced. Now there is no clear definition of psychological endurance levels and no accurate measurement tools yet.

METHODS

This study first proposes the concept of psychological endurance threshold (PET) and defines that as: "the psychological state threshold of human objective physiological characteristics and outbreaks of abnormal behavior led by subjective cognitive level difference". The study hypothesizes that human behavior is related to it, and constructs multiple measurement method tools to measure it.

RESULTS

Here we show PET exists objectively and can be measured exactly by methods such as psychological endurance threshold measurement table, experience evaluation, dopamine level detection, and genetic testing. In particular, PET is determined by AKT1, PRDM4, and BAX which are the natural markers of PET.

CONCLUSIONS

The significance of this study is to discover people with abnormal expression of AKT1, PRDM4, and BAX who have lower PET and tend to commit abnormal behavior more easily. Understanding PET will enable people to make self-adjustment or to intervene by professionals as soon as possible and in a timely manner in the face of various negative stimuli in work and life, especially for people with lower PET, people should intervene as early as possible to reduce the harm to the individual, family and society.

A Proximal Perspective on Disgust

The functional basis of disgust in disease avoidance is widely accepted; however, there is disagreement over what disgust is. This is a significant problem, as basic questions about disgust require knowing if single/multiple forms/processes exist. We address this issue with a new model with one form of disgust generated by multiple processes: (a) pure disgust experienced during gastrointestinal illness; (b) somatosensory disgust elicited by specific cues that activate the pure disgust state; (c) anticipatory disgust elicited by associations between distance cues for somatosensory disgust and requiring threat evaluation; (d) simulated disgusts elicited by imagining somatosensory and anticipatory disgust and frequently involving other emotions. Different contamination processes interlink (a–d). The implications of our model for fundamental questions about disgust (e.g., emotion status; continuation into animals) are examined.

The structure and function of pathogen disgust

Researchers have long noted that many of the multiple elicitors of disgust have some relation to infectious disease. There is an emerging consensus that disgust evolved in Animalia to direct the behaviours that reduce risk of infection, so-called 'parasite avoidance theory'. If this is correct, then the disgust motive should be structured in a manner that reflects the ways in which infectious disease can be avoided. In this study, we generated a set of items based on the epidemiology of disease transmission. These were then rated for their capacity to elicit disgust by a large, predominantly North American/UK sample and subjected to factor analysis to identify latent variables. While a number of plausible factor solutions emerged, Velicer's MAP (minimum average partial) test suggested six domains: atypical appearance, lesions, sex, hygiene, food and animals. This structure did not exactly mirror the transmission routes of infections, as we initially predicted, but it may rather reflect distinct kinds of behavioural tasks involved in avoiding disease. This finding makes sense from the perspective of a cognitive system that evolved under selection for a behavioural response to threats from the social and biological environment. We suggest that regularly occurring types of infectious disease problems have produced regularities in the domain structure of pathogen disgust and discuss the implications of these results for understanding the structure, function and measurement of motives such as disgust in humans and other animals.This article is part of the Theo Murphy meeting issue 'Evolution of pathogen and parasite avoidance behaviours'.

Consumption, contact and copulation: how pathogens have shaped human psychological adaptations

Disgust is an emotion intimately linked to pathogen avoidance. Building on prior work, we suggest disgust is an output of programmes that evolved to address three separate adaptive problems: what to eat, what to touch and with whom to have sex. We briefly discuss the architecture of these programmes, specifying their perceptual inputs and the contextual factors that enable them to generate adaptive and flexible behaviour. We propose that our sense of disgust is the result of these programmes and occurs when information-processing circuitries assess low expected values of consumption, low expected values of contact or low expected sexual values. This conception of disgust differs from prior models in that it dissects pathogen-related selection pressures into adaptive problems related to consumption and contact rather than assuming just one pathogen disgust system, and it excludes moral disgust from the domain of disgust proper. Instead, we illustrate how low expected values of consumption and contact as well as low expected sexual values can be used by our moral psychology to provide multiple causal links between disgust and morality.This article is part of the Theo Murphy meeting issue 'Evolution of pathogen and parasite avoidance behaviours'.

Why do people vary in disgust?

People vary in the degree to which they experience disgust toward—and, consequently, avoid—cues to pathogens. Prodigious work has measured this variation and observed that it relates to, among other things, personality, psychopathological tendencies, and moral and political sentiments. Less work has sought to generate hypotheses aimed at explaining why this variation exists in the first place, and even less work has evaluated how well data support these hypotheses. In this paper, we present and review the evidence supporting three such proposals. First, researchers have suggested that variability reflects a general tendency to experience anxiety or emotional distress. Second, researchers have suggested that variability arises from parental modelling, with offspring calibrating their pathogen avoidance based on their parents' reactions to pathogen cues. Third, researchers have suggested that individuals calibrate their disgust sensitivity to the parasite stress of the ecology in which they develop. We conclude that none of these hypotheses is supported by existing data, and we propose directions for future research aimed at better understanding this variation.

This article is part of the Theo Murphy meeting issue ‘Evolution of pathogen and parasite avoidance behaviours’.

CROCUFID: A Cross-Cultural Food Image Database for Research on Food Elicited Affective Responses

We present CROCUFID: a CROss-CUltural Food Image Database that currently contains 840 images, including 479 food images with detailed metadata and 165 images of non-food items. The database includes images of sweet, savory, natural, and processed food from Western and Asian cuisines. To create sufficient variability in valence and arousal we included images of food with different degrees of appetitiveness (fresh, unfamiliar, molded or rotten, spoiled, and partly consumed). We used a standardized photographing protocol, resulting in high resolution images depicting all food items on a standard background (a white plate), seen from a fixed viewing (45°) angle. CROCUFID is freely available under the CC-By Attribution 4.0 International license and hosted on the OSF repository. The advantages of the CROCUFID database over other databases are its (1) free availability, (2) full coverage of the valence - arousal space, (3) use of standardized recording methods, (4) inclusion of multiple cuisines and unfamiliar foods, (5) availability of normative and demographic data, (6) high image quality and (7) capability to support future (e.g., virtual and augmented reality) applications. Individuals from the United Kingdom (N = 266), North-America (N = 275), and Japan (N = 264) provided normative ratings of valence, arousal, perceived healthiness, and desire-to-eat using visual analog scales (VAS). In addition, for each image we computed 17 characteristics that are known to influence affective observer responses (e.g., texture, regularity, complexity, and colorfulness). Significant differences between groups and significant correlations between image characteristics and normative ratings were in accordance with previous research, indicating the validity of CROCUFID. We expect that CROCUFID will facilitate comparability across studies and advance experimental research on the determinants of food-elicited emotions. We plan to extend CROCUFID in the future with images of food from a wide range of different cuisines and with non-food images (for applications in for instance neuro-physiological studies). We invite researchers from all parts of the world to contribute to this effort by creating similar image sets that can be linked to this collection, so that CROCUFID will grow into a truly multicultural food database.

Lack of response to disgusting food in the hypothalamus and related structures in Prader Willi syndrome

Objective

To investigate, based on a putative abnormal neural processing of disgusting signals in Prader Willi syndrome (PWS) patients, the brain response to visual representations of disgusting food in PWS using functional MRI (fMRI).

Methods

Twenty-one genetically-confirmed PWS patients, 30 age- and sex-matched and 28 BMI-matched control subjects viewed a movie depicting disgusting food-related scenes interspersed with scenes of appetizing food while fMRI was acquired. Brain activation maps were compared between groups and correlated with disgust and hunger ratings.

Results

At the cortical level, the response to disgusting food representations in PWS patients was qualitatively similar to that of control subjects, albeit less extensive, and engaged brain regions typically related to visually-evoked disgust, such as the anterior insula/frontal operculum, the lateral frontal cortex and visual areas. By contrast, activation was almost absent in limbic structures directly concerned with the regulation of instinctive behavior robustly activated in control subjects, such as the hypothalamus, amygdala/hippocampus and periaqueductal gray.

Conclusions

Our study provides novel insights into the neural substrates of appetite control in a genetically-mediated cause of obesity. The presence of significant cortical changes further indicates that PWS patients consciously process disgusting stimuli, but the virtual absence of response in deep, limbic structures suggests that disgusting signals do not adequately reach the primary brain system for the appetite control.

•

We report an abnormal pattern of brain response to images of disgusting food in PWS.

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The activation demonstrated by PWS patients was restricted to the cerebral cortex.

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Higher subjective disgust ratings were associated with greater insula activation.

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In contrast, the neural response was almost absent in deep subcortical structures.

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Disgusting signals may not adequately reach a main brain system for appetite control.

Vegetarians' and omnivores' affective and physiological responses to images of food

Many vegetarians report that meat is unpleasant, but little else is known about their affective responses to meat and non-meat foods. Here we explored affective responses to food images in vegetarians and omnivores and tested the hypothesis that vegetarians have global differences in affective processing (e.g., increased disgust sensitivity). We presented pictures of different food items and recorded participants' affective experience while we recorded peripheral physiology. We found that vegetarians' self-reported experience of meat meal images was less pleasant than omnivores', but that other food images were equally pleasant across the two groups. Moreover, vegetarians and omnivores had strikingly similar physiological responses to all food images - including meat meals. We interpret these results from a psychological constructionist perspective, which posits that individuals conceptualize changes in their bodily states in ways that match their beliefs, such that increased sympathetic nervous system activity may be conceptualized as an experience of excitement about a delicious meat meal for omnivores but as an experience of displeasure for a vegetarian who believes meat is cruel, wasteful, impure, or unhealthy. This interpretation is consistent with emerging neuroscience evidence that the brain constructs experience by predicting and making meaning of internal sensations based on past experience and knowledge.

Sex Differences in Disgust: Why Are Women More Easily Disgusted Than Men?

Women have consistently higher levels of disgust than men. This sex difference is substantial in magnitude, highly replicable, emerges with diverse assessment methods, and affects a wide array of outcomes—including job selection, mate choice, food aversions, and psychological disorders. Despite the importance of this far-reaching sex difference, sound theoretical explanations have lagged behind the empirical discoveries. In this article, we focus on the evolutionary-functional level of analysis, outlining hypotheses capable of explaining why women have higher levels of disgust than men. We present four hypotheses for sexual disgust and six for pathogen disgust, along with testable predictions. Discussion focuses on additional new hypotheses and on future research capable of adjudicating among these competing, but not mutually exclusive, hypotheses.

Avoidance of biological contaminants through sight, smell and touch in chimpanzees

Avoiding biological contaminants is a well-known manifestation of the adaptive system of disgust. In theory, animals evolved with such a system to prevent pathogen and parasite infection. Bodily products are human-universal disgust elicitors, but whether they also elicit avoidance behaviour in non-human primates has yet to be tested. Here, we report experimental evidence that potential exposure to biological contaminants (faeces, blood, semen), as perceived via multiple sensory modalities (visual, olfactory, tactile), might influence feeding decisions in chimpanzees (Pan troglodytes troglodytes)-our closest phylogenetic relatives. Although somewhat mixed, our results do show increased latencies to feed, tendencies to maintain greater distances from contaminants and/or outright refusals to consume food in test versus control conditions. Overall, these findings are consistent with the parasite avoidance theory of disgust, although the presence of biological contaminants did not preclude feeding entirely. The avoidance behaviours observed hint at the origins of disgust in humans, and further comparative research is now needed.

Task-Based and Questionnaire Measures of Inhibitory Control Are Differentially Affected by Acute Food Restriction and by Motivationally Salient Food Stimuli in Healthy Adults

Adaptive eating behaviors are dependent on an interaction between motivational states (e.g., hunger) and the ability to control one's own behavior (inhibitory control). Indeed, behavioral paradigms are emerging that seek to train inhibitory control to improve eating behavior. However, inhibitory control is a multifaceted concept, and it is not yet clear how different types (e.g., reactive motor inhibition, proactive motor inhibition, reward-related inhibition) are affected by hunger. Such knowledge will provide insight into the contexts in which behavioral training paradigms would be most effective. The present study explored the impact of promoting a "need" state (hunger) together with motivationally salient distracting stimuli (food/non-food images) on inhibitory control in 46 healthy adults. Participants attended two study sessions, once after eating breakfast as usual and once after acute food restriction on the morning of the session. In each session, participants completed questionnaires on hunger, mood and inhibitory control, and undertook task-based measures of inhibitory control, and had physiological measurements (height, weight, and blood glucose) obtained by a researcher. Acute food restriction influenced task-based assessments but not questionnaire measures of inhibitory control, suggesting that hunger affects observable behavioral control but not self-reported inhibitory control. After acute food restriction, participants showed greater temporal discounting (devaluation of future rewards), and subjective hunger and these were inversely correlated with stop accuracy on the stop signal task. Finally, participants generally responded faster when food-related distractor images were presented, compared to non-food images, independent of state. This suggests that although food stimuli motivate approach behavior, stimulus relevance does not impact inhibitory control in healthy individuals, nor interact with motivational state. These findings may provide some explanation for poorer inhibitory control often reported in studies of individuals who practice restraint over eating.

The evolutionary psychology of hunger

An evolutionary psychological perspective suggests that emotions can be understood as coordinating mechanisms whose job is to regulate various psychological and physiological programs in the service of solving an adaptive problem. This paper suggests that it may also be fruitful to approach hunger from this coordinating mechanism perspective. To this end, I put forward an evolutionary task analysis of hunger, generating novel a priori hypotheses about the coordinating effects of hunger on psychological processes such as perception, attention, categorization, and memory. This approach appears empirically fruitful in that it yields a bounty of testable new hypotheses.

Behavioral Bias for Food Reflected in Hand Movements: A Preliminary Study with Healthy Subjects

Palatable food induces general approach tendencies when compared to nonfood stimuli. For eating disorders, the modification of an attention bias toward food was proposed as a treatment option. Similar approaches have been efficient for other psychiatric conditions and, recently, successfully incorporated approach motivation. The direct impact of attentional biases on spontaneous natural behavior has hardly been investigated so far, although actions may serve as an intervention target, especially seeing the recent advances in the field of embodied cognition. In this study, we addressed the interplay of motor action execution and cognition when interacting with food objects. In a Virtual Reality (VR) setting, healthy participants repeatedly grasped or warded high-calorie food or hand-affordant ball objects using their own dominant hand. This novel experimental paradigm revealed an attention-like bias in hand-based actions: 3D objects of food were collected faster than ball objects, and this difference correlated positively with both individual body mass index and diet-related attitudes. The behavioral bias for food in hand movements complements several recent experimental and neurophysiological findings. Implications for the use of VR in the treatment of eating-related health problems are discussed.

Rivalry of homeostatic and sensory-evoked emotions: Dehydration attenuates olfactory disgust and its neural correlates

Neural correlates have been described for emotions evoked by states of homeostatic imbalance (e.g. thirst, hunger, and breathlessness) and for emotions induced by external sensory stimulation (such as fear and disgust). However, the neurobiological mechanisms of their interaction, when they are experienced simultaneously, are still unknown. We investigated the interaction on the neurobiological and the perceptional level using subjective ratings, serum parameters, and functional magnetic resonance imaging (fMRI) in a situation of emotional rivalry, when both a homeostatic and a sensory-evoked emotion were experienced at the same time. Twenty highly dehydrated male subjects rated a disgusting odor as significantly less repulsive when they were thirsty. On the neurobiological level, we found that this reduction in subjective disgust during thirst was accompanied by a significantly reduced neural activity in the insular cortex, a brain area known to be considerably involved in processing of disgust. Furthermore, during the experience of disgust in the satiated condition, we observed a significant functional connectivity between brain areas responding to the disgusting odor, which was absent during the stimulation in the thirsty condition. These results suggest interference of conflicting emotions: an acute homeostatic imbalance can attenuate the experience of another emotion evoked by the sensory perception of a potentially harmful external agent. This finding offers novel insights with regard to the behavioral relevance of biologically different types of emotions, indicating that some types of emotions are more imperative for behavior than others. As a general principle, this modulatory effect during the conflict of homeostatic and sensory-evoked emotions may function to safeguard survival.

Human Emotions: An Evolutionary Psychological Perspective

Evolutionary approaches to the emotions have traditionally focused on a subset of emotions that are shared with other species, characterized by distinct signals, and designed to solve a few key adaptive problems. By contrast, an evolutionary psychological approach (a) broadens the range of adaptive problems emotions have evolved to solve, (b) includes emotions that lack distinctive signals and are unique to humans, and (c) synthesizes an evolutionary approach with an information-processing perspective. On this view, emotions are superordinate mechanisms that evolved to coordinate the activity of other programs in the solution of adaptive problems. We illustrate the heuristic value of this approach by furnishing novel hypotheses for disgust and sexual arousal and highlighting unexplored areas of research.

Emotional communication in the context of joint attention for food stimuli: effects on attentional and affective processing

Guided by distinct theoretical frameworks (the embodiment theories, shared-signal hypothesis, and appraisal theories), we examined the effects of gaze direction and emotional expressions (joy, disgust, and neutral) of virtual characters on attention orienting and affective reactivity of participants while they were engaged in joint attention for food stimuli contrasted by preference (disliked, moderately liked, and liked). The participants were exposed to videos of avatars looking at food and displaying facial expressions with their gaze directed either toward the food only or toward the food and participants consecutively. We recorded eye-tracking responses, heart rate, facial electromyography (zygomatic, corrugator, and levator labii regions), and food wanting/liking. The avatars' joy faces increased the participants' zygomatic reactions and food liking, with mutual eye contact boosting attentional responses. Eye contact also fostered disgust reactions to disliked food, regardless of the avatars' expressions. The findings show that joint attention for food accompanied by face-to-face emotional communication elicits differential attentional and affective responses. The findings appear consistent with the appraisal theories of emotion.

Balancing competing motives: adaptive trade-offs are necessary to satisfy disease avoidance and interpersonal affiliation goals

The current research provides novel evidence for motivational trade-offs between the two fundamental human goals of pursuing social affiliation and avoiding disease. In Study 1, participants completed a writing prime that manipulated inclusionary status and found that socially excluded participants indicated lower feelings of current disease susceptibility compared with control and socially included participants. In Study 2, participants were included or excluded via Cyberball and then indicated their preferences for symmetrical versus asymmetrical faces. Socially excluded participants displayed lower preferences for symmetrical faces--a cue associated with greater disease resistance. Finally, in Study 3, participants were primed with either disease threat or a general negative affective state and then indicated their current affiliation interest. Activated disease concerns uniquely led participants to display less interest in social affiliation. Taken together, affiliation needs result in disease avoidance down-regulation to aid reaffiliation, whereas disease concerns result in affiliation down-regulation to facilitate pathogen avoidance.

Infection-avoidance behaviour in humans and other animals

Compared with living free, the parasitic way of life has many attractions. Parasites create problems for all animals. Potential hosts can respond by learning to live with parasites (tolerance), actively fighting them (resistance), or they can avoid becoming infected in the first place (avoidance). I propose here a new classification of avoidance behaviour according to the epidemiology of infection risk, where animals must avoid (i) conspecifics, (ii) parasites and their vectors, (iii) parasite-rich environments, and (iv) niche infestation. I further explore how the disgust adaptive system, which coordinates avoidance behaviour, may form a continuum with the immune system through the sharing of signalling pathways, sites of action, and evolutionary history.

Effects of subjective sexual arousal on sexual, pathogen, and moral disgust sensitivity in women and men

The present experiment tested a novel method of manipulating subjective sexual arousal to examine the effects of sexual arousal on disgust sensitivity. Participants were instructed to employ their own preferred methods of achieving sexual or physiological arousal in the privacy of their own home to reach a target state of arousal. Participants then completed the Three-Domain Disgust Scale (Tybur, Lieberman, & Griskevicius, 2009), which measures sensitivity to sexual, pathogen, and moral disgust. The sexual arousal manipulation caused large, homogenous increases in sexual arousal in women and men. In women, sexual arousal (but not physiological arousal) significantly reduced sensitivity to sexual disgust and marginally increased sensitivity to pathogen disgust. In men, sexual arousal did not decrease disgust sensitivity in any domain. Findings support the evolutionary hypothesis that sexual arousal inhibits sexual disgust, which facilitates an organism's willingness to engage in high-risk, but evolutionarily necessary, reproductive behaviors, an effect that could be particularly important for women.