Scientists discover the smell of death has surprising influence on human behaviour

Research has revealed that the smell of death can have a surprising effect on human behaviour without us even realising it.

Published in Frontiers in Psychology, scientists explained that bodies release a compound called putrescine which is essentially the scent behind decomposing animals or humans. Putrescine is also found in small quantities in human semen and is often likened to the smell of bad breath, according to Biogone.

In the 2015 study, researchers wanted to explore whether putrescine signalled a threat in humans that triggered defensive behaviours.

The study was broken down into four experiments.

In experiment one, participants were assigned one of three scents (putrescine, ammonia, or water) on cotton wool pads an hour before the study started. They were then asked to click a red dot on a computer test as fast as they could with the researchers tracking their vigilance.

Experiment two delved into escape behaviour. The same three scents were administered and participants were asked to walk 80 metres away. The time it took them was monitored.

Participants were then asked to do a word-stem task after being exposed to the three scents. For example, a letter was missing from a word and they were required to use an appropriate letter to make it whole. They were asked to take a 60-metre walk with the time tracked.

Lastly, in experiment four, putrescine's influence on defensive behaviours was explored – even when the smell couldn't be detected by the person. Participants were exposed to small concentrations of putrescine and ammonia and were asked to read an essay from an author who was critical of Western values. They were asked their thoughts, and the speed they finished the questionnaire dictated their desire to escape.

Overall, the study revealed that exposure to putrescine correlated with heightened vigilance. Participants seemed to walk faster and portray more defensive behaviours.

"As a whole, the findings indicate that even brief exposure to putrescine mobilizes threat management responses designed to cope with environmental threats. These are the first results to show that a specific chemical compound (putrescine) can be processed as a threat signal," the authors said.

"An important direction for future research will be to understand the precise nature of the threat produced by putrescine (e.g., microbial, predatory). Our view is that putrescine is relevant to both of these domains, though the immediate context should determine which type of threat is more primary."

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