Disgusting clusters: trypophobia as an overgeneralised disease avoidance response

The social learning account of trypophobia

Trypophobia is the condition in which individuals report a range of negative emotions when viewing clusters of small holes. Since the phenomenon was first described in the peer-reviewed literature a decade ago, 49 papers have appeared together with hundreds of news articles. There has also been much discussion on various Internet forums, including medical and health-related websites. In the present article, we examine the degree to which the phenomenon is caused by a form of social learning, specifically, its ubiquitous social media presence. We also examined its prevalence among the broad population. In Experiment 1 (n = 2,558), we assessed whether younger people and females (i.e., greater social media users) are more sensitive to trypophobic stimuli, as predicted by the social media hypothesis. In Experiment 2 (n = 283), we examined whether sensitivity to trypophobic stimuli and rates of trypophobia is greater in people who are aware of the condition's existence, as opposed to those who have never heard of the phenomenon. In line with the social media theory, results showed that younger people and females are indeed more susceptible to trypophobia. However, 24% of trypophobic individuals have never heard of the condition. Overall, these data suggest that both social learning and non-social learning contribute to trypophobia. We also find that the prevalence of trypophobia is approximately 10%.

Contamination in Trypophobia: investigating the role of disgust

Trypophobia is a relatively common aversion to clusters of holes. There is no consensus yet on which emotions are involved in Trypophobia nor in its functional utility. This report investigates the role of disgust using contamination tasks in two studies, which contrast people with an aversion to trypophobic stimuli to those without. In Study 1, participants reported their emotional reactions to imagined contamination of trypophobic images. In Study 2, participants evaluated physically present trypophobic, disgust, fear, and control stimuli. The capacity of these stimuli to contaminate other objects was established using a chain of contagion task. Across both studies, contamination was present, however, only those with an aversion to trypophobic stimuli evidenced contamination on the chain of contagion task, a hallmark of disgust responding. Elevated levels were not only reported for disgust, but also alongside fear/anxiety. Participant reports suggest an underlying disease avoidance mechanism in Trypophobia, with trypophobic participants demonstrating an exaggerated response to such stimuli involving disgust and fear/anxiety, which is also seen in small animal phobia, BII, and C-OCD. Implications, particularly for treatment are discussed.

Effects of cluster size on trypophobic discomfort in children aged 4-9 years

It has been reported that strong discomfort associated with clusters of circles and holes (trypophobia), including lotus pod seeds, manifests in individuals as young as 4 or 5 years old. This study investigated how the size and number of circles within clusters affected discomfort levels in adults and in children aged 4-9 years. In Experiment 1, we confirmed that the remote experimental procedure could evoke discomfort when participants were presented with cluster images. The findings reveal that children as young as 4 or 5 years old consistently experienced discomfort when rating trypophobic images, even printed images rated in real time during video calls. In Experiment 2, we explored the impact of cluster size, considering both the size and number of circles, in a remote experiment. The results indicate that discomfort tended to increase with cluster size in both children and adults, with the effect becoming more pronounced with age.

Trypophobia, skin disease, and the visual discomfort of natural textures

In the last decade, the behavioral sciences have described the phenomenon of trypophobia, which is the discomfort felt by some individuals when viewing images containing clusters of bumps or holes. One evolutionary hypothesis for this phenomenon is that this visual discomfort represents an adaptation which helps organisms avoid skin disease and/or ectoparasites. Even though trypophobic imagery and disease imagery are both examples of visual textures, to date there has been no comparison of the visual discomfort elicited by these two specific kinds of textures within the larger context of the visual comfort elicited by natural texture imagery more generally. In the present study, we administered the Trypophobia Questionnaire (TQ) and recorded the visual comfort ratings elicited by a large set of standard natural texture images, including several trypophobic and skin disease images. In two independent samples, we found that while all observers find skin diseases uncomfortable to view, only those scoring high on the TQ rated trypophobic imagery equally uncomfortable. Comparable effects were observed using both standard ANOVA procedures as well as linear mixed effects modeling. Comparing the ratings of both high-TQ and low-TQ participants to the standard textures, we find remarkably consistent rank-order preferences, with the most unpleasant textures (as rated by both groups) exhibiting qualitative similarities to trypophobic imagery. However, we also find that low-level image statistics which have been previously shown to affect visual comfort are poor predictors of the visual comfort elicited by natural textures, including trypophobic and disease imagery. Our results suggest that a full understanding of the visual comfort elicited by natural textures, including those arising from skin disease, will ultimately depend upon a better understanding of cortical areas specialized for the perception of surface and material properties, and how these visual regions interact with emotional brain areas to evoke appropriate behavioral responses, like disgust.

Is trypophobia real?

Approximately 10-18% of the adult population experience some form of anxiety when viewing clusters of small holes. 'Trypophobia' has been the subject of much discussion within the peer-reviewed literature, news outlets, health-related websites and social media. However, there is some scepticism surrounding the phenomenon. It is often stated that the condition is not recognised by the American Psychiatric Association, and not listed as a phobia in the DSM-5. It has also been claimed that trypophobia is no more than a particularly successful internet meme. In this editorial, I argue that such criticisms are misplaced. There is, for instance, no list of phobias in the DSM-5; only criteria that determine phobia classification. Using these criteria, as well as personal testimonials, trypophobia is clearly a phobia. Furthermore, the meme hypothesis cannot account for the fact that the phenomenon existed long before the internet.

Pupillary Responses to Dot Patterns on a Human Face Background

Dots on natural backgrounds can elicit significant pupillary constrictions within the entire image phase associated with parasympathetic activation, suggesting disgust rather than fear. Although studies have reported that dots on faces elicit stronger disgust than dots on non-face backgrounds, it remains unclear whether dots on a face elicit stronger pupil constrictions than non-face backgrounds. Pupillometry was used while viewing dots on faces and compared with luminance- and spatial frequency-controlled images (dots on phase-scrambled faces) and luminance-controlled images (face only, phase-scrambled faces). Relative pupillary constrictions were elicited when dots were placed on faces and phase-scrambled faces; however, the response to dots on faces did not differ significantly from that to the control stimuli. Approximately 3-5 s after stimulus onset, pupillary responses to dots on faces recovered to baseline faster than those to dots on phase-scrambled faces with a larger pupil size. The initial pupillary constrictions observed are consistent with those in response to dots on natural backgrounds, suggesting that regardless of the background, dots may stimulate parasympathetic activation and elicit disgust rather than fear. The faster recovery from the pupil constriction and larger pupil size in the later phase may be caused by a dynamic balance between the sympathetic and parasympathetic neuronal activities.

Parasitic manipulation or side effects? The effects of past Toxoplasma gondii and Borrelia spp. infections on human personality and cognitive performance are not mediated by impaired health

Bacteria Borrelia burgdorferi s. l. and even more the protist Toxoplasma gondii Nicolle et Manceaux, 1908, are known to affect the behaviour and mental health of their animal and human hosts. Both pathogens infect a significant fraction of human population, both are neurotropic and survive in the host's body for a long time. While latent infections were thought to be clinically asymptomatic, recent studies suggest otherwise, revealing adverse effects on human health. It was hypothesised that the specific behavioural effects of these pathogens may be side effects of general health impairments in infected individuals. This hypothesis was tested using about one hour-long survey consisting of questionnaires and performance tests on a cohort of 7,762 members of the internet population. Results showed that individuals infected with T. gondii reported worse physical and mental health, and those infected with Borrelia spp. reported worse physical health than uninfected controls. Furthermore, infected and noninfected individuals differed in several personality traits, including conscientiousness, pathogen disgust, injury disgust, Machiavellianism, narcissism, tribalism, anti-authoritarianism, intelligence, reaction time, and precision. While the majority of behavioural effects associated with Borrelia infection were similar to those associated with Toxoplasma infection, some differences were observed, such as performance in the Stroop test. Path analyses and nonparametric partial Kendall correlation tests showed that these effects were not mediated by impaired health in infected individuals, contradicting the side effects hypothesis.

Excessive fear of clusters of holes, its interaction with stressful life events and the association with anxiety and depressive symptoms: large epidemiological study of young people in Hong Kong

BACKGROUND

Excessive and persistent fear of clusters of holes, also known as trypophobia, has been suggested to reflect cortical hyperexcitability and may be associated with mental health risks. No study, however, has yet examined these associations in representative epidemiological samples.

AIMS

To examine the prevalence of trypophobia in a population-representative youth sample, its association with mental health and functioning, and its interaction with external stress.

METHOD

A total of 2065 young people were consecutively recruited from a household-based epidemiological youth mental health study in Hong Kong. Trypophobia, symptoms of anxiety, depression and stress, and exposure to personal stressors were assessed. Logistic regression was used to assess the relationships between trypophobia and mental health. Potential additive and interaction effects of trypophobia and high stress exposure on mental health were also tested.

RESULTS

The prevalence of trypophobia was 17.6%. Trypophobia was significantly associated with severe symptoms of anxiety (odds ratio (OR) = 1.83, 95% CI = 1.32-2.53), depression (OR = 1.78, 95% CI = 1.24-2.56) and stress (OR = 1.68, 95% CI = 1.11-2.53), even when accounting for sociodemographic factors, personal and family psychiatric history, resilience and stress exposure. Dose-response relationships were observed, and trypophobia significantly potentiated the effects of stress exposure on symptom outcomes, particularly for depressive symptoms. Those with trypophobia also showed significantly poorer functioning across domains and poorer health-related quality of life.

CONCLUSIONS

Screening for trypophobia in young people may facilitate early risk detection and intervention, particularly among those with recent stress exposure. Nevertheless, the generally small effect sizes suggest that other factors have more prominent roles in determining recent mental health outcomes in population-based samples; these should be explored in future work.

Parasites either reduce or increase host vulnerability to fishing: a case study of a parasitic copepod and its salmonid host

Parasites generally increase host vulnerability to predators via host manipulation for trophic transmission and reduction of host activities. Predators also select prey depending on the parasite infection status. Despite such parasites' roles in prey-predator interactions in wild animals, how parasites affect human hunting probability and resource consumption remains unknown. We examined the effects of the ectoparasitic copepod Salmincola cf. markewitschi on fish vulnerability to angling. We found that infected fish were less vulnerable compared with non-infected fish when the fish body condition was low, which was probably due to reduced foraging activity. On the contrary, infected fish were more vulnerable when the host body condition was high, probably due to the compensation of parasites' negative effects. A Twitter analysis also suggested that people avoided eating fish with parasites and that anglers' satisfaction decreased when captured fish were parasitized. Thus, we should consider how animal hunting is affected by parasites not only for catchability but also for avoiding parasite infection sources in many local regions.

Preschool children aged 4 to 5 years show discomfort with trypophobic images

The fear or disgust of clustered patterns, such as honeycomb or lotus seed pods, is known as trypophobia. A previous developmental study reported that 4-year-old children prefer neutral images over clustered images. However, whether those results indicated higher rating scores for trypophobic images has been controversial. In this study, we examined discomfort with trypophobic images in adults and children aged 4-9 years using an identical experimental procedure. A modified rating scale applicable for children was used that was based on the established Trypophobia Scale for adults. The participants were required to rate five trypophobic and five neutral images on four rating items (disgusting, fear, feel itchiness, and like) on a 4-point scale ranging from 1 (not at all) to 4 (very much). The participants in all age groups indicated higher rate scores for trypophobic images than for neutral images in terms of 'disgust', 'fear', and 'feeling itchiness', whereas they indicated higher scores for neutral images than for trypophobic images in terms of 'like'. These results suggest that children aged 4-5 years have responses comparable to the responses of adults with respect to trypophobic and neutral images; thus, trypophobia appears to emerge at least by the age of 4-5 years.

A social media network analysis of trypophobia communication

Trypophobia has attracted scientific attention in recent years. Few related studies have recruited participants using online methods, and even less is known about health communication in an environment where trypophobia was first widely discussed (i.e., the Internet). This study describes communication patterns in a Facebook group for trypophobia by detecting frequent topics, top contributors, and their discourses. We identified key commenters and performed word frequency analysis, word co-occurrence analysis, topic modeling, and content analysis. Impactful users posted and replied more often when discussing peer-reviewed science. Triggering content was actively removed by the group administrators. A wide variety of triggers not discussed in trypophobia-related literature were frequently mentioned. However, there was a lack of discussion on peer-reviewed treatments. The combination of a few expert and many supportive amateur gatekeepers willing to understand trypophobia, along with active monitoring by administrators, might contribute to in-group trust and the sharing of peer-reviewed science by top users of the trypophobia Facebook group.

Depth perception between dots and the background face reduces trypophobic discomfort

BACKGROUND

Studies have shown that viewing a cluster of dots evokes feelings of discomfort in viewers and that the discomfort becomes especially strong when the dots are placed on background images of human skin. This phenomenon has been explained by the physical properties and spatial and semantic relationships between the dots and the background. However, it was not known whether the perceived, as well as the physical, spatial relationships contributes to the generation of discomfort.

METHODS

We evoked illusory depth perception between black dots and the background face by drawing shadow-like gray dots around the black dots, while keeping the same black dots at the same positions, and examined whether illusory depth perception could increase or decrease discomfort. In each trial, participants viewed one of the following types of facial images: (a) face-only (face without dots), (b) a cluster of black dots on the face, (c) a cluster of gray dots on the face, and (d) a cluster of black dots and shadow-like gray dots on the face. After seeing each picture, they evaluated how much discomfort they felt from viewing the picture using a Likert scale and reported whether they perceived depth between the dots and the face.

RESULTS

Participants felt discomfort toward all three types of faces with dots, that is, faces with black dots, gray dots, and both. However, interestingly, participants felt less discomfort when both black and gray dots were presented on the face than when only black dots were presented. The participants perceived depth between the black dots and the face in 85% of the trials with black dots and shadow-like gray dots, and there was a significant correlation between discomfort and frequency of depth perception. However, in the trials with black dots only and gray dots only, they perceived depth in only 18% and 27% of the trials, respectively, and the correlations between the frequencies of depth perception and discomfort were not significant.

CONCLUSIONS

Our results suggest that the perceived spatial relationship, such as attached vs. separate, as well as the physical spatial relationship, contribute to the generation of discomfort.

Star finches Neochmia ruficauda have a visual preference for white dot patterns: a possible case of trypophilia

Many animals have polka dot patterns on their body surface, some of which are known to have signalling functions; however, their evolutionary origins remain unclear. Dot patterns can trigger a fear response (trypophobia) in humans and are known to function as aposematic signals in non-human animals, suggesting that dots may deserve attention for biological reasons. Interestingly in many birds, plumage dot patterns serve for social/sexual signalling. To understand their evolution, we have focused on the sensory bias hypothesis, which predicts the role of pre-existing sensory preference driven by natural selection in shaping signal design. Our previous phylogenetic comparative study supported the hypothesis and showed that diet-driven visual preference promoted the evolution of plumage patterns, as there was an evolutionary correlation between termite-eating (white roundish gregarious prey) and the presence of plumage dot patterns in species of the family Estrildidae. This suggests that these species possess an intrinsic preference for dots. To test this, we compared the responses of an Estrildid species with dot plumage pattern (star finch Neochmia ruficauda) towards simultaneously presented monochrome-printed white dot vs white stripe patterns under both food-deprived and -supplied conditions. Overall, star finches preferred dots to stripes. They showed foraging-like behaviours almost only toward dots when hungry and gazed at dots frequently even when food was available, suggesting both hunger-related and hunger-neutral dot preferences. These results are rather surprising, given how strongly the subjects were attracted to abstract dot patterns without organic structure, but provided good support for the sensory bias hypothesis.

Evaluating the 'skin disease-avoidance' and 'dangerous animal' frameworks for understanding trypophobia

ABSTRACTTrypophobia refers to the extreme negative reaction when viewing clusters of circular objects. Two major evolutionary frameworks have been proposed to account for trypophobic visual discomfort. The skin disease-avoidance (SD) framework proposes that trypophobia is an over-generalised response to stimuli resembling pathogen-related skin diseases. The dangerous animal (DA) framework posits that some dangerous organisms and trypophobic stimuli share similar visual characteristics. Here, we performed the first experimental manipulations which directly compare these two frameworks by superimposing trypophobic imagery onto multiple image categories to evaluate changes in comfort. Participants from two countries (United States and Croatia) were evaluated on several measures, including general trypophobia levels, perceived vulnerability to disease, and generalised anxiety. Several analyses showed stronger changes in comfort in the human skin condition (hand, feet, and chest images) compared to the dangerous animal condition (snake and spider images). Furthermore, participants with higher levels of trypophobia showed significantly stronger changes in comfort in the skin condition than the dangerous animal condition, with comparable effects obtained across nationalities. Several variables entered as covariates failed to significantly account for this effect. The present work is the first to experimentally test both evolutionary frameworks of trypophobia, with results supporting the skin disease-avoidance framework.

The Perceived Beauty of Convex Polygon Tilings: The Influence of Regularity, Curvature, and Density

Polygon tilings in natural and man-made objects show great variety. Unlike previous studies that have mainly focused on their classification and production methods, this study aimed at exploring factors that may contribute to the perceived beauty of convex polygon tilings. We analyze the dimensions of regularity, curvature, and density, as well as individual differences. Triangle tilings and hexagon tilings were tested in Experiment 1 and 2, respectively. The results showed that the perceived beauty of convex polygon tilings can be enhanced by higher levels of regularity and nonobvious local curvature. Surprisingly, the effect of density appeared to be different, with the dense triangle tilings and the less dense hexagon tilings scoring higher than the reverse. We discuss a possible explanation based on trypophobia caused by different types of polygons, as well as the observers' personality trait of agreeableness.

An exploration of the nomological network of trypophobia

BACKGROUND

Trypophobia is characterised by an aversion to or even revulsion for patterns of holes or visual stimuli featuring such patterns. Past research has shown that trypophobic stimuli trigger emotional and physiological reactions, but relatively little is known about the antecedents, prodromes, or simply covariates of trypophobia.

AIM

The goals of this study were (a) to draw the contours of the nomological network of trypophobia by assessing the associations of symptoms of trypophobia with several constructs that were deemed relevant from past research on anxiety disorders and specific phobias, (b) to compare such associations with those found for symptoms of spider phobia and blood and injection phobia (alternative dependent variables), and (c) to investigate the main effect of gender on symptoms of trypophobia and replicate the association of gender with symptoms of spider phobia and blood and injection phobia (higher scores for women).

METHODS

Participants (N = 1,134, 53% men) in this cross-sectional study completed an online questionnaire assessing the constructs of interest.

RESULTS

Most assessed constructs typically associated with anxiety disorders (neuroticism, conscientiousness, anxiety sensitivity, trait anxiety, disgust sensitivity, and disgust propensity) were also associated with trypophobia in the predicted direction. All of these constructs were also associated with spider phobia and blood and injection phobia. Behavioral inhibition was negatively associated with trypophobia and spider phobia-contrary to what was expected, but positively with blood and injection phobia. We found no gender difference in trypophobia, whereas women scored higher on spider phobia and blood and injection phobia.

DISCUSSION

Although some differences were observed, the nomological network of trypophobia was largely similar to that of spider phobia and blood and injection phobia. Further studies are needed to clarify similarities and dissimilarities between trypophobia and specific phobia.

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.

Priming with skin-problems increases fear of clusters

Trypophobia is induced by viewing multiple clustered objects. To date, several studies have investigated why certain people experience discomfort when looking at clustered patterns. Recently, “involuntary protection against dermatosis” (IPAD) hypothesis was proposed to explain the causes of trypophobia. The IPAD hypothesis suggests that involuntary aversive responses to skin diseases cause discomfort in response to image clusters. However, this idea has not been fully investigated empirically. Therefore, the present study used a modified version of the priming procedure and tested whether the activation of the concept of skin-related diseases affected the evaluation of trypophobic images. In Experiment 1, participants engaged in a lexical decision task in which words related to skin problems, negative events, or neutral events were presented. Then, they evaluated the discomfort of trypophobic, negative, and neutral images. The results indicated that participants evaluated trypophobic images as more discomforting after they were exposed to skin-problem-related words, whereas the exposure to words related to skin-problems did not enhance the discomfort of negative images. These findings demonstrate that the association with skin-related problems increases the discomfort of trypophobic images. In Experiment 2, we further tested the reproducibility of the priming effect observed in Experiment 1 and investigated the effect of priming with words related to COVID-19 in the context of a spreading infection. Contrary to predictions, no priming effect was produced by either skin-related words or COVID-19-related words. Future studies should further explore the causal relationship of the association between skin disease and trypophobia.

Considerations of the proximate mechanisms and ultimate functions of disgust will improve our understanding of cleansing effects

To understand the consequences of cleansing, Lee and Schwarz favor a grounded procedures perspective over recently developed disgust theory. We believe that this position stems from three errors: (1) interpreting cleansing effects as broader than they are; (2) not detailing the proximate mechanisms underlying disgust; and (3) not detailing adaptive function versus system byproducts when developing the grounded procedures perspective.

Trypophobia: Heart rate, heart rate variability and cortical haemodynamic response

BACKGROUND

Trypophobia is a common condition in which sufferers are averse to images of small holes arranged in clusters.

METHODS

We used photo-plethysmography to examine cardiovascular correlates and near infrared spectroscopy to examine cortical correlates of the phenomenon in order to validate the Trypophobia Questionnaire and explore the several interlinked explanations of the disorder.

RESULTS

Trypophobic images were found to increase both heart rate and heart rate variability, but only in individuals with high scores on the Trypophobia Questionnaire. Trypophobic images were also found to elicit larger haemodynamic responses in posterior cortical areas, but again only in individuals with high scores.

LIMITATIONS

The results are consistent with a contribution from both parasympathetic and sympathetic systems.

CONCLUSION

The data demonstrate the validity of the Trypophobia Questionnaire and show an involvement not only of the autonomic system but cortical mechanisms including cortical hyperexcitability.

Object Clusters or Spectral Energy? Assessing the Relative Contributions of Image Phase and Amplitude Spectra to Trypophobia

Trypophobia refers to the visual discomfort experienced by some people when viewing clustered patterns (e.g., clusters of holes). Trypophobic images deviate from the 1/f amplitude spectra typically characterizing natural images by containing excess energy at mid-range spatial frequencies. While recent work provides partial support for the idea of excess mid-range spatial frequency energy causing visual discomfort when viewing trypophobic images, a full factorial manipulation of image phase and amplitude spectra has yet to be conducted in order to determine whether the phase spectrum (sinusoidal waveform patterns that comprise image details like edge and texture elements) also plays a role in trypophobic discomfort. Here, we independently manipulated the phase and amplitude spectra of 31 Trypophobic images using a standard Fast Fourier Transform (FFT). Participants rated the four different versions of each image for levels of visual comfort, and completed the Trypophobia Questionnaire (TQ). Images having the original phase spectra intact (with either original or 1/f amplitude) explained the most variance in comfort ratings and were rated lowest in comfort. However, images with the original amplitude spectra but scrambled phase spectra were rated higher in comfort, with a smaller amount of variance in comfort attributed to the amplitude spectrum. Participant TQ scores correlated with comfort ratings only for images having the original phase spectra intact. There was no correlation between TQ scores and comfort levels when participants viewed the original amplitude / phase-scrambled images. Taken together, the present findings show that the phase spectrum of trypophobic images, which determines the pattern of small clusters of objects, plays a much larger role than the amplitude spectrum in determining visual discomfort.

Trypophobia as an urbanized emotion: comparative research in ethnic minority regions of China

Trypophobia is a strong emotion of disgust evoked by clusters of holes or round objects (e.g., lotus seed pod). It has become increasingly popular and been studied since 2010s, mainly in the West and Japan. Considering this, trypophobia might be a modern emotion, and hence urbanization possibly plays key roles in trypophobia. To address this issue, we compared the degree of trypophobia between urban and less urban people in China. In an experiment, we asked participants about their degree of discomfort from trypophobic images. The results showed that trypophobia occurred in both groups, although the effect size was larger in urban than less urban people. Moreover, post-experimental interviews and post-hoc analyses revealed that older people in less urban area did not experience as much trypophobia. Our findings suggest that trypophobia links to urbanization and age-related properties.

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'.

Enhanced early visual processing in response to snake and trypophobic stimuli

Background

Trypophobia refers to aversion to clusters of holes. We investigated whether trypophobic stimuli evoke augmented early posterior negativity (EPN).

Methods

Twenty-four participants filled out a trypophobia questionnaire and watched the random rapid serial presentation of 450 trypophobic pictures, 450 pictures of poisonous animals, 450 pictures of snakes, and 450 pictures of small birds (1800 pictures in total, at a rate of 3 pictures/s). The EPN was scored as the mean activity at occipital electrodes (PO3, O1, Oz, PO4, O2) in the 225–300 ms time window after picture onset.

Results

The EPN was significantly larger for snake pictures than for the other categories, and significantly larger for trypophobic pictures and poisonous animal pictures than for bird pictures. Remarkably, the scores on the trypophobia questionnaire were correlated with the EPN amplitudes for trypophobic pictures at the occipital cluster (r = −.46, p = .025).

Conclusions

The outcome for the EPN indicates that snakes, and to a somewhat lesser extent trypophobic stimuli and poisonous animals, trigger early automatic visual attention. This supports the notion that the aversion that is induced by trypophobic stimuli reflects ancestral threat and has survival value. The possible influence of the spectral composition of snake and trypophobic stimuli on the EPN is discussed.

Face-Inversion Effect on Disgust Evoked by a Cluster of Dots

A cluster of dots such as lotus seed pods evokes extremely strong disgust when it is placed on human and animal skins. However, few empirical studies have examined the role of the background image, such as skin, in the generation of disgust. In this study, we investigated whether the orientation of background faces influences the disgust evoked by the dot pattern. The participants were asked to evaluate disgust to an upright, inverted, or phase-scrambled face image with or without a cluster of dots on it and then complete a questionnaire measuring trypophobia proneness (Trypophobia Questionnaire). The results suggested that disgust was intensified by the background faces, especially by the upright faces. The intensification of disgust in the upright face was correlated positively with the Trypophobia Questionnaire scores. The results indicated a face-inversion effect on the disgust to the dot pattern, suggesting a significant role of the background image.

Rasch analysis of the Trypophobia Questionnaire

Objective

This study aimed to assess Rasch-based psychometric properties of the Trypophobia Questionnaire measuring proneness to trypophobia, which refers to disgust and unpleasantness induced by the observation of clusters of objects (e.g., lotus seed pods).

Results

Rasch analysis was performed on data from 582 healthy Japanese adults. The results suggested that Trypophobia Questionnaire has a unidimensional structure with ordered response categories and sufficient person and item reliabilities, and that it does not have differential item functioning across sexes and age groups, whereas the targeting of the scale leaves room for improvements. When items that did not fit the Rasch model were removed, the shortened version showed slightly improved psychometric properties. However, results were not conclusive in determining whether the full or shortened version is better for practical use. Further assessment and validation are needed.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3245-5) contains supplementary material, which is available to authorized users.

Pupillometry reveals the physiological underpinnings of the aversion to holes

An unusual, but common, aversion to images with clusters of holes is known as trypophobia. Recent research suggests that trypophobic reactions are caused by visual spectral properties also present in aversive images of evolutionary threatening animals (e.g., snakes and spiders). However, despite similar spectral properties, it remains unknown whether there is a shared emotional response to holes and threatening animals. Whereas snakes and spiders are known to elicit a fear reaction, associated with the sympathetic nervous system, anecdotal reports from self-described trypophobes suggest reactions more consistent with disgust, which is associated with activation of the parasympathetic nervous system. Here we used pupillometry in a novel attempt to uncover the distinct emotional response associated with a trypophobic response to holes. Across two experiments, images of holes elicited greater constriction compared to images of threatening animals and neutral images. Moreover, this effect held when controlling for level of arousal and accounting for the pupil grating response. This pattern of pupillary response is consistent with involvement of the parasympathetic nervous system and suggests a disgust, not a fear, response to images of holes. Although general aversion may be rooted in shared visual-spectral properties, we propose that the specific emotion is determined by cognitive appraisal of the distinct image content.

Trypophobia: What Do We Know So Far? A Case Report and Comprehensive Review of the Literature

In this article, we describe the case of a girl who suffers from a phobia to repetitive patterns, known as trypophobia. This condition has not yet been recognised by diagnostic taxonomies such as the Diagnostic and Statistical Manual of Mental Disorders. Trypophobia usually involves an intense and disproportionate fear towards holes, repetitive patterns, protrusions, etc., and, in general, images that present high-contrast energy at low and midrange spatial frequencies. It is commonly accompanied by neurovegetative symptoms. In the case we present here, the patient also suffered from generalised anxiety disorder and was treated with sertraline. After she was diagnosed, she showed symptoms of both fear and disgust towards trypophobic images. After some time following treatment, she only showed disgust towards said images. We finish this case report presenting a comprehensive literature review of the peer reviewed articles we retrieved after an exhaustive search about trypophobia, we discuss how this case report contributes to the understanding of this anxiety disorder, and what questions future studies should address in order to achieve a better understanding of trypophobia.

Involuntary protection against dermatosis: A preliminary observation on trypophobia

Objective

Trypophobia refers to the intense negative emotions evoked by exposure to repeated visual patterns like a honeycomb. We propose a cognitive mechanism that can explain why such negative emotions are triggered by trypophobic objects, primarily through automatic and involuntary avoidance of skin diseases, which is also called as the Involuntary Protection Against Dermatosis (IPAD) hypothesis.

Results

We asked 856 participants to evaluate the discomfort evoked by trypophobic images and to report their past and current skin-related medical problems. Results showed that participants with a history of skin problems rated the pictures as evoking high discomfort as compared to those without skin problems. We conducted another survey to replicate the original survey using additional 690 participants, which confirmed the reliability of the current findings. The current study presents preliminary observational data that supports the IPAD hypothesis and suggests ways to reduce maladaptive emotional reactions toward trypophobic objects.