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PLoS ONEPhysiologyPeer-reviewed journal article

Subjective and psychophysiological response to pictures of ancestral and modern threats: not all evolutionary threats are alike

Iveta ŠtolhoferováiD, Tereza HladíkováiD, Markéta JanovcováiD, Šárka Peterková, Daniel FryntaiD, Eva LandováiD

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Abstract

After encountering a potentially dangerous stimulus, the human body and mind might react with a cascade of physiological, emotional, and cognitive responses to minimize impending harm. However, whether this system can be activated by modern (ontogenetic) threats to the same extent as by ancestral (evolutionary) threats remains uncertain, since the existing results are ambiguous. In this study, we aimed to compare the skin resistance (SR) response to ancestral and modern threats; the focal categories were venomous snakes, heights, airborne diseases, and firearms. We collected recordings of 119 participants, about 30 per threat category, supplemented by participants rating of the stimuli according to elicited fear. Results showed that participants reacted (SR change) with higher probability to all experimental categories than to control stimuli, with the most frequent reactions to photos simulating the threat of heights, followed by snakes, firearms, and airborne diseases. The largest amplitudes, indicating response intensity, were observed for heights but also for venomous snakes. Further examination showed that higher subjective fear corresponded to an increased probability of SR change. Although the results suggest a slight advantage for ancestral threats, responses to the threat of heights differed in several respects from responses to snakes, demonstrating that ancestrality-based categorisation cannot capture all aspects of the response. Moreover, both ancestral and modern threats can evoke similar electrodermal responses, depending on subjective stimulus salience and/or threat relevance.

In-depth summary

Claude Opus 5.5 · xhigh effort · 8 Nov 2026 · from the full text of version 1 (16 Jan 2026) · CC BY 4.0

Skin resistance responses in 119 non-phobic adults were most frequent and largest for height images; venomous snakes and firearms did not differ in response probability.

It is still unclear whether modern threats engage autonomic defence as strongly as evolutionarily ancestral ones, and electrodermal activity has rarely been used to compare them. The study tests two ancestral threats (snakes, heights) and two modern ones (airborne disease, firearms) in a general population sample, and relates skin resistance responses to each person's own fear ratings.

Key results

  1. ShownEvery threat category raised the probability of a skin resistance (SR) change above the leaf control images. Heights images far exceeded the other threats, which did not differ from one another.

    Response probability: heights 0.420 (z=13.43, p<0.001), venomous snakes 0.203, firearms 0.188, airborne diseases 0.156 (p=0.032) vs control 0.122. Heights exceeded every other threat (p<0.001); the remaining threats did not differ (p>0.05). Model vs null χ^2=234.62, marginal R^2=0.059, conditional R^2=0.334. · Physiological reactions toward stimuli of…

  2. ShownResponse amplitude was higher than control only for the two ancestral categories, heights and venomous snakes. Amplitudes for firearms and airborne disease were indistinguishable from leaves, and heights again ranked highest among the threats.

    Mean amplitude: heights 20.74 kΩ (t=8.72, p<0.001), venomous snakes 12.24 kΩ (t=2.59, p=0.010), firearms 11.23 kΩ (p=0.178), airborne diseases 9.80 kΩ (p=0.989) vs control 9.79 kΩ. Heights was highest among threats (p<0.001); marginal R^2=0.091, conditional R^2=0.360. · Physiological reactions toward stimuli of…

  3. ShownSubjective fear and SR change were linked in both directions of analysis for heights, firearms and airborne diseases, but not for venomous snakes, even though snakes received the highest mean fear ratings.

    Fear rating predicting SR probability: heights z=5.53 (p<0.001), firearms z=2.14 (p=0.033), airborne z=2.12 (p=0.034), snakes z=0.91 (p=0.363). CLMM with SR predicting rating: heights z=6.36, firearms z=2.60, airborne z=2.17, snakes z=0.73 (p=0.466). Mean fear: snakes 3.41, firearms 3.16, heights 2.79, airborne 2.57. · Effect of subjective fear on physiological…; Effect of physiological response on subjective…

  4. SuggestedTrait anxiety did not track SR amplitude. Scores on a snake-fear questionnaire correlated moderately with mean SR amplitude to snake images, while the threat-specific scales for heights, airborne disease and firearms showed no significant correlation.

    STAI-X2 vs mean amplitude: N=106, Spearman -0.161 (p=0.100) for all stimuli and -0.142 (p=0.146) for threats only. SNAQ-12 vs threat-only amplitude: N=27, Spearman 0.424, p=0.027 (all stimuli 0.335, p=0.090). AQ avoidance (N=30) and modified ATGV (N=22) correlations were not significant. · Relationship between general anxiousness and…; Relationship between sensitivity to specific…

  5. SuggestedStimulus category had a statistically significant but very small effect on SR onset latency. Only airborne disease images produced earlier onsets than controls.

    Latency model vs null χ^2=11.78, p=0.019, marginal R^2=0.009. Airborne diseases 2.36 s (t=-3.07, p=0.002) vs control 2.68 s. Firearms 2.53 s (p=0.159), heights 2.54 s (p=0.103) and snakes 2.57 s (p=0.233) did not differ from control. · Temporal course of SR change; Limitations and future directions

Methods, data and reproducibility

Between-subjects design: each participant viewed 28 images from one threat category interleaved with leaf controls (the two opening controls were dropped, leaving 28 analysed), each shown for 5 s during finger skin resistance recording, then rated fear on a 7-point Likert scale. Analyses used binomial, Gamma and linear mixed models, cumulative link mixed models and Spearman correlations.

  • Adult Czech, Slovak and other Central European volunteers, each viewing one threat category; 96 women and 23 men, aged 18 to 74 · human · n = 119 analysed participants (about 30 per threat category)
  • Trial-level skin resistance measurements (56 stimuli per sequence), with trials affected by participant movement excluded · human · n = 6,664 measurements; 167 excluded
  • Threat images (viperid snakes, heights, airborne disease, firearms) and grey-background leaf controls from OASIS, IAPS, SMID, EmoMadrid, Pixabay, Wikimedia, Flickr and author photos · n = 28 images per threat category; 30 control images
  • Psychometric questionnaire scores (STAI-X2, TDDS, CSBS, FCV-19S, C-19SS, plus SNAQ-12, AQ or modified ATGV depending on category) · human · n = N=106 for STAI-X2; N=22 to 30 per category-specific scale
  • Raw skin resistance recordings deposited on Zenodo; processed data in Supplementary Tables S4-5 · human · 10.5281/zenodo.17722322
Methods & tools
Multifunction Biotelemetry Support System for Psychophysiology Monitoring VLV3, RStudio 4.3.1 (R), lme4 (binomial and Gamma GLMM, LMM), ordinal (cumulative link mixed models), performance (marginal and conditional R^2), k-cluster analysis of stimuli, State-Trait Anxiety Inventory-X2 (STAI-X2), Twelve-Item Snake Questionnaire (SNAQ-12), Acrophobia Questionnaire (AQ), Attitudes Toward Guns and Violence Questionnaire (ATGV, modified), Coronavirus Safety Behaviours Scale (CSBS), TDDS, FCV-19S and C-19SS questionnaires
Reagents & environment
RStudio 4.3.1 (R Core Team, 2023) with the lme4, ordinal and performance packages; package versions are not given.
Reproducibility gaps
No analysis code or scripts are shared. Processed data are in Supplementary Tables S4-5 and raw data on Zenodo; stimulus photo sources are listed in Table S1, but no deposit of the stimulus set is mentioned.
Limitations (6)
  • Because each participant saw only one threat category, differences between categories may partly reflect individual sensitivity to that threat. The authors note that only a within-subjects design with fewer stimuli per category could fully resolve this. · stated by the authors
  • Only phasic SR peaks within a 1 to 5 s window were analysed, and the authors state the study lacked the power to compare the temporal dynamics of responses across categories. · stated by the authors
  • Stimuli were shown above the threshold of awareness for 5 s, so automatic and conscious contributions can only be inferred indirectly, by contrasting SR with subjective ratings rather than by using backward masking. · stated by the authors
  • A k-cluster analysis testing whether individual stimuli grouped into their categories by SR parameters alone proved of limited power, which the authors attribute to too few SR parameters being available. · stated by the authors
  • The only significant questionnaire association (SNAQ-12, N=27, p=0.027) came from many Spearman tests with no reported multiple-comparison correction, and 80.7 % of the sample were women, which limits generalization. · noted in this summary
  • The CSBS correlations for airborne disease (0.335, p=0.090; -0.142, p=0.146) duplicate the values reported for SNAQ-12 and STAI-X2, which suggests a transcription error in that result. · noted in this summary

Read this if you study electrodermal or other autonomic responses to threat, or test fear module and preparedness accounts by comparing evolutionary and modern fear stimuli.

Citations
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