Toward a reliable detection of arachnophobia: subjective, behavioral, and neurophysiological measures of fear response.

Introduction: The administration of questionnaires presents an easy way of obtaining important knowledge about phobic patients. However, it is not well known how these subjective measurements correspond to the patient's objective condition. Our study aimed to compare scores on questionnaires and image evaluation to the objective measurements of the behavioral approach test (BAT) and the neurophysiological effect of spiders extracted from fMRI measurements. The objective was to explore how reliably subjective statements about spiders and physiological and behavioral parameters discriminate between phobics and non-phobics, and what are the best predictors of overall brain activation. Methods: Based on a clinical interview, 165 subjects were assigned to either a "phobic" or low-fear "control" group. Finally, 30 arachnophobic and 32 healthy control subjects (with low fear of spiders) participated in this study. They completed several questionnaires (SPQ, SNAQ, DS-R) and underwent a behavioral approach test (BAT) with a live tarantula. Then, they were measured in fMRI while watching blocks of pictures including spiders and snakes. Finally, the respondents rated all the visual stimuli according to perceived fear. We proposed the Spider Fear Index (SFI) as a value characterizing the level of spider fear, computed based on the fMRI measurements. We then treated this variable as the "neurophysiological effect of spiders" and examined its contribution to the respondents' fear ratings of the stimuli seen during the fMRI using the redundancy analysis (RDA). Results: The results for fear ranks revealed that the SFI, SNAQ, DS-R, and SPQ scores had a significant effect, while BAT and SPQ scores loaded in the same direction of the first multivariate axis. The SFI was strongly correlated with both SPQ and BAT scores in the pooled sample of arachnophobic and healthy control subjects. Discussion: Both SPQ and BAT scores have a high informative value about the subject's fear of spiders and together with subjective emotional evaluation of picture stimuli can be reliable predictors of spider phobia. These parameters provide easy and non-expensive but reliable measurement wherever more expensive devices such as magnetic resonance are not available. However, SFI still reflects individual variability within the phobic group, identifying individuals with higher brain activation, which may relate to more severe phobic reactions or other sources of fMRI signal variability.

Do Spiders Ride on the Fear of Scorpions? A Cross-Cultural Eye Tracking Study.

Deep fear of spiders is common in many countries, yet its origin remains unexplained. In this study, we tested a hypothesis based on recent studies suggesting that fear of spiders might stem from a generalized fear of chelicerates or fear of scorpions. To this end, we conducted an eye tracking experiment using a spontaneous gaze preference paradigm, with spiders and scorpions (previously neglected but crucial stimuli) as threatening stimuli and grasshoppers as control stimuli. In total, 67 participants from Somaliland and 67 participants from the Czech Republic were recruited and presented with a sequence of paired images. Both Somali and Czech people looked longer (total duration of the gaze) and more often (number of fixations) on the threatening stimuli (spiders and scorpions) when presented with a control (grasshopper). When both threatening stimuli were presented together, Somali participants focused significantly more on the scorpion, whereas in Czech participants, the effect was less pronounced, and in Czech women it was not significant. This supports the hypothesis that fear of spiders originated as a generalized fear of scorpions. Moreover, the importance of spiders as fear-eliciting stimuli may be enhanced in the absence of scorpions in the environment.

Specificity of spiders among fear- and disgust-eliciting arthropods: Spiders are special, but phobics not so much.

To investigate a specificity of spiders as a prototypical fear- and disgust-eliciting stimuli, we conducted an online experiment. The respondents rated images of 25 spiders, 12 non-spider chelicerates, and 10 other arthropods on a fear and disgust 7-point scale. The evaluation of 968 Central European respondents confirmed the specificity of spiders among fear- and disgust-eliciting arthropods and supported the notion of spiders as a cognitive category. We delineated this category as covering extant spider species as well as some other chelicerates bearing a physical resemblance to spiders, mainly whip spiders and camel spiders. We suggested calling this category the spider-like cognitive category. We discussed evolutionary roots of the spider-like category and concluded that its roots should be sought in fear, with disgust being secondary of the two emotions. We suggested other chelicerates, e.g., scorpions, might have been important in formation and fixation of the spider-like category. Further, we investigated an effect of respondent's sensitivity to a specific fear of spiders on evaluation of the stimuli. We found that suspected phobic respondents were in their rating nearly identical to those with only high fear of spiders and similar to those with only moderate fear of spiders. We concluded that results based on healthy respondents with elevated fear should also be considered relevant for arachnophobia research.

Venomous snakes elicit stronger fear than nonvenomous ones: Psychophysiological response to snake images.

Snakes have been important ambush predators of both primates and human hunter-gatherers throughout their co-evolutionary history. Viperid snakes in particular are responsible for most fatal venomous snakebites worldwide and thus represent a strong selective pressure. They elicit intense fear in humans and are easily recognizable thanks to their distinctive morphotype. In this study, we measured skin resistance (SR) and heart rate (HR) in human subjects exposed to snake pictures eliciting either high fear (10 venomous viperid species) or disgust (10 nonvenomous fossorial species). Venomous snakes subjectively evaluated as frightening trigger a stronger physiological response (higher SR amplitude) than repulsive non-venomous snakes. However, stimuli presented in a block (more intense stimulation) do not trigger a stronger emotional response compared to sequentially presented stimuli (less intense stimulation). There are significant interindividual differences as subjects with high fear of snakes confronted with images of viperid snakes show stronger, longer-lasting, and more frequent changes in SR and higher HR compared to low-fear subjects. Thus, we show that humans demonstrate a remarkable ability to discriminate between dangerous viperids and harmless fossorial snakes, which is also reflected in distinct autonomous body responses.

Emotional Reaction to Fear- and Disgust-Evoking Snakes: Sensitivity and Propensity in Snake-Fearful Respondents.

This paper continues our previous study in which we examined the respondents' reaction to two morphologically different snake stimuli categories - one evoking exclusively fear and another evoking exclusively disgust. Here we acquired Likert-type scale scores of fear and disgust evoked by the same snake stimuli by a total of 330 respondents. Moreover, we collected data about the respondents' age, gender, education, snake fear [Snake Questionnaire (SNAQ)], and disgust propensity [Disgust Scale-Revised (DS-R)], and we analyzed the effect of these variables on the emotional scores (with special focus on snake-fearful respondents). In addition, we collected the SNAQ and DS-R scores from the respondents tested in the previous study using the rank-ordering method to directly compare the results of these two approaches. The results showed that non-fearful respondents give high scores of fear to the fear-eliciting snakes and high scores of disgust to the disgust-eliciting snakes, but they give low scores of the other emotional dimension (disgust/fear) to each. In contrast, snake-fearful respondents not only give higher fear and disgust scores to the respective snake stimuli, but they also give high scores of fear to the disgust-eliciting snakes and high scores of disgust to the fear-eliciting snakes. Both Likert-scale scores and rank-ordering data show that the clear border dividing both snake stimuli categories dissolves when evaluated by the snake-fearful respondents.

Scary and nasty beasts: Self-reported fear and disgust of common phobic animals.

Animal phobias are one of the most prevalent mental disorders. We analysed how fear and disgust, two emotions involved in their onset and maintenance, are elicited by common phobic animals. In an online survey, the subjects rated 25 animal images according to elicited fear and disgust. Additionally, they completed four psychometrics, the Fear Survey Schedule II (FSS), Disgust Scale - Revised (DS-R), Snake Questionnaire (SNAQ), and Spider Questionnaire (SPQ). Based on a redundancy analysis, fear and disgust image ratings could be described by two axes, one reflecting a general negative perception of animals associated with higher FSS and DS-R scores and the second one describing a specific aversion to snakes and spiders associated with higher SNAQ and SPQ scores. The animals can be separated into five distinct clusters: (1) non-slimy invertebrates; (2) snakes; (3) mice, rats, and bats; (4) human endo- and exoparasites (intestinal helminths and louse); and (5) farm/pet animals. However, only snakes, spiders, and parasites evoke intense fear and disgust in the non-clinical population. In conclusion, rating animal images according to fear and disgust can be an alternative and reliable method to standard scales. Moreover, tendencies to overgeneralize irrational fears onto other harmless species from the same category can be used for quick animal phobia detection.

Human evaluation of amphibian species: a comparison of disgust and beauty.

Animals can evoke a wide range of emotions helping us to choose a quick and appropriate reaction towards them: approach or avoidance in general. This work has focused on disgust evoked by amphibians in humans as well as perceived beauty. Due to the high morphological variability of recent amphibian taxa, we examined humans' cognitive categorisation of 101 amphibian photos and the effect of stimuli characteristics on disgust evaluation or beauty perception of individual groups/species. We also explored how respondents' characteristics, e.g. gender, age and disgust sensitivity (DS-R) influence the disgust and beauty evaluation of picture stimuli on a 7-point Likert scale. The scores of disgust and beauty evaluation were strongly negatively correlated, representing the opposite ends of a single axis, further referred to as the index of preference. The most preferred amphibians belonged to anurans, whereas the least preferred ones were mostly worm-like, legless and small-eyed caecilians. Additional analyses of morphologically diverse anurans showed that species with a round body shape, short forelegs, small eyes, warts, pink and grey colouration, or dark and dull colouration were perceived as disgusting or ugly. The effect of gender and age were only marginal; however, people with higher disgust sensitivity rated amphibians as more disgusting and less beautiful, which might support the hypothesis of a possible disgust involvement in animal fears and phobias. This topic has implications not only for the nature conservation decisions of globally endangered amphibians but also for understanding the evolution of disgust and its generalisation to harmless animals.

Human Attitude toward Reptiles: A Relationship between Fear, Disgust, and Aesthetic Preferences.

Focusing on one group of animals can bring interesting results regarding our attitudes toward them and show the key features that our evaluation of such animals is based on. Thus, we designed a study of human perception of all reptiles focusing on the relationship between perceived fear, disgust, and aesthetic preferences and differences between snakes and other reptiles. Two sets containing 127 standardized photos of reptiles were developed, with one species per each subfamily. Respondents were asked to rate the animals according to fear, disgust, and beauty on a seven-point Likert scale. Evaluation of reptile species shows that people tend to perceive them as two clearly distinct groups based on their similar morphotype. In a subset of lizards, there was a positive correlation between fear and disgust, while disgust and fear were both negatively correlated with beauty. Surprisingly, a positive correlation between fear and beauty of snakes was revealed, i.e., the most feared species also tend to be perceived as beautiful. Snakes represent a distinct group of animals that is also reflected in the theory of attentional prioritization of snakes as an evolutionary relevant threat.

Beauty ranking of mammalian species kept in the Prague Zoo: does beauty of animals increase the respondents' willingness to protect them?

Aesthetic preferences for animals correspond with the species' presence in the worldwide zoos and influence the conservation priorities. Here, we investigated the relationship between the willingness of respondents to protect mammals and some attributed characteristics such as their aesthetic beauty. Further, several methodological aspects of measuring mammalian beauty were assessed. Animal beauty was associated not only with the respondents' willingness to protect the species but also with its attributed dangerousness and usefulness. We found that the most preferred animals were carnivores and ungulates, whilst smaller species of rodents and afrosoricids were unpopular. The main characteristics determining that an animal will be ranked as beautiful were complex fur pattern and body shape. We demonstrated that the position of mammalian species along the 'beauty' axis is surprisingly stable, no matter the form (illustrations vs photographs), context of stimulus presentation (several number of stimuli per family vs one randomly selected species per family), or the method of beauty evaluation (relative order vs Likert's scale).

Judging Others by Your Own Standards: Attractiveness of Primate Faces as Seen by Human Respondents.

The aspects of facial attractiveness have been widely studied, especially within the context of evolutionary psychology, which proposes that aesthetic judgements of human faces are shaped by biologically based standards of beauty reflecting the mate quality. However, the faces of primates, who are very similar to us yet still considered non-human, remain neglected. In this paper, we aimed to study the facial attractiveness of non-human primates as judged by human respondents. We asked 286 Czech respondents to score photos of 107 primate species according to their perceived "beauty." Then, we analyzed factors affecting the scores including morphology, colors, and human-likeness. We found that the three main primate groups were each scored using different cues. The proportions of inner facial features and distinctiveness are cues widely reported to affect human facial attractiveness. Interestingly, we found that these factors also affected the attractiveness scores of primate faces, but only within the Catarrhines, i.e., the primate group most similar to humans. Within this group, human-likeness positively affected the attractiveness scores, and facial extremities such as a prolonged nose or exaggerated cheeks were considered the least attractive. On the contrary, the least human-like prosimians were scored as the most attractive group. The results are discussed in the context of the "uncanny valley," the widely discussed empirical rule.