Fear-eliciting images of modern and ancestral threats are equally likely to evoke physiological reactions, despite their distinct evolutionary origins, according to a study published March 18, 2026, in the open-access journal PLOS One by Eva Landová from Charles University, the Czech Republic, and colleagues. However, ancestral threats such as heights and venomous snakes trigger greater skin resistance responses, a measure of sweating, compared to modern threats and harmless stimuli.
Fear is an adaptive emotion that can warn us and prepare us to promptly and adequately respond to threats. 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 threats to the same extent as ancestral threats has been unclear.
To fill this knowledge gap, Landová and colleagues compared the physiological and emotional responses of 119 participants to photos of two ancestral and two modern types of threats: venomous snakes, heights, firearms, and airborne disease (e.g., pictures of medical staff or people wearing masks, sneezing, or coughing). They also presented control photos of leaves. The researchers measured skin resistance (i.e., how much the skin impedes electrical current), which decreases with increased sweating, and the participants rated the stimuli according to the level of fear they elicited.
The researchers found that participants experienced a greater sweating reaction to photos of all presented threats compared to control photos. Reactions to photos of heights were most common, with reaction frequency being similar across snakes, firearms, and airborne disease. Reactions were observed to be most intense for heights and venomous snakes, compared to firearms and airborne disease.
Although the results suggested a slightly heightened response to the ancestral threats of heights and venomous snakes, responses to the threat of heights differed in several respects from responses to the threat of venomous snakes, demonstrating that the ancestral origin of such threats cannot fully explain all aspects of the response.
Venomous snakes were rated subjectively as the most fear-eliciting threat of those presented, though those who reported the greatest fear were not necessarily those who showed greatest physiological reactions. Subjective fear ratings correlated better with sweating responses for the heights, firearms, and airborne disease threats.
The authors note that skin resistance changes occur relatively slowly; as they presented several threats to participants within a short space of time, they might have detected overlapping physiological responses to multiple threats. Additionally, their study design did not enable separation of instinctive responses from conscious responses, which might differ by threat category. Nonetheless, they suggest that the physiological responses they measured argue against a simple distinction between ancestral and modern threats, calling for more research to further our understanding of how we react to a range of perceived threats.
Eva Landová adds: "The key finding is already in the title: not all evolutionary threats are alike. We found clear differences in how people respond to heights and venomous snakes – in fact, their responses to these two types of threats differed in almost every aspect."
Iveta Štolhoferová adds: "For snake images, participants' subjective reports did not match their skin resistance responses. This suggests that reactions to snakes are influenced by unconscious processing more strongly than reactions to other threatening stimuli."
Markéta Janovcová adds: "I always enjoy selecting the stimulus images. I often try to guess which ones will trigger the strongest reactions – but even after many years of research, it is still surprisingly hard to predict."
In your coverage, please use this URL to provide access to the freely available article in PLOS One: https://plos.io/4ssJ6KY
Citation: Štolhoferová I, Hladíková T, Janovcová M, Peterková Š, Frynta D, Landová E (2026) Subjective and psychophysiological response to pictures of ancestral and modern threats: Not all evolutionary threats are alike. PLoS One 21(3): e0343680. https://doi.org/10.1371/journal.pone.0343680
Author countries: Czech Republic
Funding: This project has been supported by the Czech Scientific Foundation (GAČR), project No. 22-13381S, awarded to EL, https://www.gacr.cz/en/ . The funder did not play any role in the study design, data collection, analysis, decision to publish, or preparation of the manuscript.
