Snakes Represent Emotionally Salient Stimuli That May Evoke Both Fear and Disgust

doi:10.3389/fpsyg.2019.01085

. 2019 May 9:10:1085.

doi: 10.3389/fpsyg.2019.01085. eCollection 2019.

Snakes Represent Emotionally Salient Stimuli That May Evoke Both Fear and Disgust

S Rádlová ¹, M Janovcová ^{1

2}, K Sedláčková ^{1

2}, J Polák ^{1

3}, D Nácar ¹, Š Peléšková ¹, D Frynta ^{1

2}, E Landová ^{1

2}

Affiliations

PMID: 31143154
PMCID: PMC6521895
DOI: 10.3389/fpsyg.2019.01085

Snakes Represent Emotionally Salient Stimuli That May Evoke Both Fear and Disgust

S Rádlová et al. Front Psychol. 2019.

. 2019 May 9:10:1085.

doi: 10.3389/fpsyg.2019.01085. eCollection 2019.

Authors

S Rádlová ¹, M Janovcová ^{1

2}, K Sedláčková ^{1

2}, J Polák ^{1

3}, D Nácar ¹, Š Peléšková ¹, D Frynta ^{1

2}, E Landová ^{1

2}

Affiliations

¹ National Institute of Mental Health, Klecany, Czechia.
² Department of Zoology, Faculty of Science, Charles University, Prague, Czechia.
³ Department of Psychology, Faculty of Arts, Charles University, Prague, Czechia.

PMID: 31143154
PMCID: PMC6521895
DOI: 10.3389/fpsyg.2019.01085

Abstract

Humans perceive snakes as threatening stimuli, resulting in fast emotional and behavioral responses. However, snake species differ in their true level of danger and are highly variable in appearance despite the uniform legless form. Different snakes may evoke fear or disgust in humans, or even both emotions simultaneously. We designed three-step-selection experiments to identify prototypical snake species evoking exclusively fear or disgust. First, two independent groups of respondents evaluated 45 images covering most of the natural variability of snakes and rated responses to either perceived fear (n = 175) or disgust (n = 167). Snakes rated as the most fear-evoking were from the family Viperidae (Crotalinae, Viperinae, and Azemiopinae), while the ones rated as the most disgusting were from the group of blind snakes called Typhlopoidea (Xenotyphlopinae, Typhlopinae, and Anomalepidinae). We then identified the specific traits contributing to the perception of fear (large body size, expressive scales with contrasting patterns, and bright coloration) and disgust (thin body, smooth texture, small eyes, and dull coloration). Second, to create stimuli evoking a discrete emotional response, we developed a picture set consisting of 40 snakes with exclusively fear-eliciting and 40 snakes with disgust-eliciting features. Another set of respondents (n = 172) sorted the set, once according to perceived fear and the second time according to perceived disgust. The results showed that the fear-evoking and disgust-evoking snakes fit mainly into their respective groups. Third, we randomly selected 20 species (10 fear-evoking and 10 disgust-evoking) out of the previous set and had them professionally illustrated. A new set of subjects (n = 104) sorted these snakes and confirmed that the illustrated snakes evoked the same discrete emotions as their photographic counterparts. These illustrations are included in the study and may be freely used as a standardized assessment tool when investigating the role of fear and disgust in human emotional response to snakes.

Keywords: affective stimuli; disgust; emotional response; fear; self-reported emotion; snakes.

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Figures

FIGURE 1

FIGURE 1

Examples of picture stimuli used in Experiments 1 (A) and 2 (B,C). The snake species are as follows, from left to right: (A) Rough-tailed Sand Boa (Eryx conicus) and Madagascar Tree Boa (Sanzinia madagascariensis), both photos by O. Šimková, used with a permission; Coral Cylinder Snake (Anilius scytale), photo by Eduardo Santos via Wikimedia Commons, modified. (B) Fear-eliciting snakes: Orlov’s Viper (Vipera orlovi), photo by Venom Tales via Flickr, modified; Ottoman Viper (Montivipera xanthina), photo by Benny Trapp via Wikimedia Commons, modified; Eastern Diamondback Rattlesnake (Crotalus adamanteus), photo by Pierson Hill, used with a permission. (C) Disgust-eliciting snakes: Southern Blind Snake (Anilios australis), photo by Stephen Zozaya, used with a permission; Northern Rubber Boa (C. bottae), photo by Gary Nafis, used with a permission; Brahminy Blind Snake (Indotyphlops braminus), photo by Alexandre Roux via Flickr, modified.

FIGURE 2

FIGURE 2

Redundancy Analysis (RDA) of the characters determining the ranks of fear and disgust elicited by snake stimuli used in Experiment 1. (A) Analysis of the fear ranks. The model explained 41.39% of the full variability, RDA1 = 0.2784% of variability and RDA2 = 0.0714% of variability. (B) Analysis of the disgust ranks. The full model explained 44.77% of the variability, RDA1 = 24.75% of variability, RDA2 = 10.76% of variability. For a better visualization of the fear/disgust ranks polarity, 10 species with the largest and lowest mean ranks of fear/disgust are mapped onto the pictures. For the description of the snake species abbreviations, see Supplementary Material 1.

FIGURE 3

FIGURE 3

PC Analyses of the fear (A,C) and disgust (B,D) ranks in the Experiments 2 (A,B) and 3 (C,D). The arrows correspond to the respondents, the dots and triangles represent the snakes. In all pictures, PC1, which explains 70.82, 64.89, 68.72, and 59.8% of the full variability in the A–D cases, respectively, clearly corresponds with the separation of the snakes from two pre-defined distinct categories, one consisting of only fear-eliciting snakes (shown in red) and other of only disgust-eliciting snakes (shown in green).

FIGURE 4

FIGURE 4

Cluster analysis (CA) of the fear (A) and disgust (B) ranks of the snakes from the Experiment 2. Both pictures show a separation of the snakes from the two pre-defined distinct categories, one consisting of only fear-eliciting snakes and other of only disgust-eliciting snakes. In case of the fear ranks (A), the respondents also identified three different groupings of the disgust-eliciting snakes set. This, however, might be a result of a non-sensual task as there might be no actual variability in fear of snakes that evoke little to no fear.

FIGURE 5

FIGURE 5

Redundancy Analysis of the characters determining the ranks of fear and disgust elicited by snake stimuli used in Experiment 3. (A) The model (RDA1) explains only 2.06% of the full variability, but it does not explain the separation of the disgust- and fear-eliciting snake categories. (B) Analysis of the disgust ranks. RDA1 explains 7.21% of the full variability and corresponds to the separation of the two snake groups. RDA2 (corresponding to age) explains 1.62% of the full variability, but does not contribute to the variability explaining the category separation.

FIGURE 6

FIGURE 6

Matrix of post hoc Friedman-Neményi comparisons among the rankings of individual snake stimuli in Experiment 3. Species are arranged in an ascending order according to their mean rank of (A) fear and (B) disgust. Friedman test of the entire matrix was highly significant. Significant comparisons (p < 0.05) are marked yellow (comparisons between fear-evoking and disgust-evoking snakes) or orange (comparisons within groups) colors. Non-significant comparisons are denoted by blue. For mean ranks and P-values, see Supplementary Material 2.

FIGURE 7

FIGURE 7

Cluster analysis of the fear (A) and disgust (B) ranks of the snakes from the Experiment 3. Both trees confirmed strict distinctiveness of the fear- and disgust-evoking clusters, regardless of the ranking type.

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References

1. Akaike H. (1998). "Information theory and an extension of the maximum likelihood principle," in Selected Papers of Hirotugu Akaike, eds Parzen E., Tanabe K., Kitagawa G. (New York, NY: Springer; ), 199–213. 10.1007/978-1-4612-1694-0_15 - DOI
1. Angyal A. (1941). Disgust and related aversions. J. Abnorm. Soc. Psychol. 36 393–412. 10.1037/h0058254 - DOI
1. Bar M., Neta M. (2006). Humans prefer curved visual objects. Psychol. Sci. 17 645–648. 10.1111/j.1467-9280.2006.01759.x - DOI - PubMed
1. Bar M., Neta M. (2007). Visual elements of subjective preference modulate amygdala activation. Neuropsychologia 45 2191–2200. 10.1016/j.neuropsychologia.200703008 - DOI - PMC - PubMed
1. Barrett L. F., Lewis M., Haviland-Jones J. M. (eds) (2016). Handbook of Emotions. New York, NY: Guilford Publications.

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[1] Akaike H. (1998). "Information theory and an extension of the maximum likelihood principle," in Selected Papers of Hirotugu Akaike, eds Parzen E., Tanabe K., Kitagawa G. (New York, NY: Springer; ), 199–213. 10.1007/978-1-4612-1694-0_15 - DOI

[2] Akaike H. (1998). "Information theory and an extension of the maximum likelihood principle," in Selected Papers of Hirotugu Akaike, eds Parzen E., Tanabe K., Kitagawa G. (New York, NY: Springer; ), 199–213. 10.1007/978-1-4612-1694-0_15 - DOI

[3] Angyal A. (1941). Disgust and related aversions. J. Abnorm. Soc. Psychol. 36 393–412. 10.1037/h0058254 - DOI

[4] Angyal A. (1941). Disgust and related aversions. J. Abnorm. Soc. Psychol. 36 393–412. 10.1037/h0058254 - DOI

[5] Bar M., Neta M. (2006). Humans prefer curved visual objects. Psychol. Sci. 17 645–648. 10.1111/j.1467-9280.2006.01759.x - DOI - PubMed

[6] Bar M., Neta M. (2006). Humans prefer curved visual objects. Psychol. Sci. 17 645–648. 10.1111/j.1467-9280.2006.01759.x - DOI - PubMed

[7] Bar M., Neta M. (2007). Visual elements of subjective preference modulate amygdala activation. Neuropsychologia 45 2191–2200. 10.1016/j.neuropsychologia.200703008 - DOI - PMC - PubMed

[8] Bar M., Neta M. (2007). Visual elements of subjective preference modulate amygdala activation. Neuropsychologia 45 2191–2200. 10.1016/j.neuropsychologia.200703008 - DOI - PMC - PubMed

[9] Barrett L. F., Lewis M., Haviland-Jones J. M. (eds) (2016). Handbook of Emotions. New York, NY: Guilford Publications.

[10] Barrett L. F., Lewis M., Haviland-Jones J. M. (eds) (2016). Handbook of Emotions. New York, NY: Guilford Publications.

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Snakes Represent Emotionally Salient Stimuli That May Evoke Both Fear and Disgust

Affiliations

Snakes Represent Emotionally Salient Stimuli That May Evoke Both Fear and Disgust

Authors

Affiliations

Abstract

Figures

References

LinkOut - more resources

Full Text Sources