Wolves and Dogs: Reaction to Fear Sweat According to Viennese Study

It emerged that both wolves and dogs reacted to the fear sweat with markedly elevated stress signals. The animals became more restless, moved less, and more frequently displayed behaviors that behavioral research considers indicators of uncertainty. The effect was statistically significant in both species, with wolves tending to react somewhat more strongly than dogs. The researchers interpret this as an indication that the ability to sniff out human fear did not arise only through thousands of years of domestication.

How the Experiment Was Conducted

The test subjects whose sweat was used in the study were female students who deliberately watched horror film scenes while collecting the samples. The films were intended to trigger measurably fear-related feelings in the young women and thereby produce the characteristic fear scent. The sweat samples obtained were then compared with neutral reference samples to rule out the possibility that the human odor alone was triggering the animals' reaction. Analysis was carried out by Capitain's team together with other staff members of the institute.

Methodologically, the researchers used a standardized scent experiment in which the animals were presented with several samples in succession. Measurements included, among other things, movement intensity, frequency of stress vocalizations, and willingness to make eye contact with a familiar person. In all three categories, values deteriorated noticeably under the influence of the fear sweat. Particularly striking was the fact that the animals remained tense even when the person in the room continued to behave calmly and in a friendly manner. In the team's assessment, this suggests that the chemical stress stimulus has an independent effect of its own.

Significance for Behavioral Research

In academic terms, the study places the result within the broader context of socio-positive communication. In behavioral research, this refers to the ability to perceive the emotions of other species and align one's own behavior accordingly. That dogs can read human moods was already known from earlier work. What is new, according to Capitain, is that wolves — the wild ancestors of domestic dogs — apparently possess similar sensory prerequisites. This pushes the ability to smell human fear back to a considerably earlier evolutionary phase than previously assumed.

For the Viennese research group, the finding also raises new questions, such as whether the animals merely react nonspecifically to stress odor or whether they interpret human fear sweat as a specific signal. The question of whether the reaction is stronger with familiar people than with strangers is also to be investigated in follow-up studies. Up to now, Capitain says, the emphasis has been more on adaptation to humans; what is now emerging is that the common ancestor of wolves and dogs already possessed the corresponding sensory foundations.

Beyond the immediate results, the researchers see practical implications, for example for dealing with olfactory stress in the training of assistance and service dogs. If it becomes better understood in the future which chemical signals dogs perceive, training environments could be designed in a more targeted way, according to the institute. In addition, the knowledge could help to better interpret unwanted stress behavior in dogs in human care.

The study joins a series of works that have examined emotional contagion between humans and dogs in recent years. The fact that the wolf, which normally keeps its distance from humans, now appears to be similarly receptive to human fear signals is regarded by the Viennese behavioral researchers as remarkable evidence of a shared sensory baseline within the canids.