Did you know that flies can smell a corpse from miles away and dig up to 2 meters deep to reach a coffin and lay their eggs? These insects are attracted by chemical signals, but necrophages are not the only ones who can detect the smell of death. Research has shown that a compound released by corpses can influence human behavior even when we don’t realize we’re smelling it.
When we die, our bodies release the “smell of death,” a compound called putrescine, responsible for the awful smell of decaying flesh, whether human or otherwise.
A 2015 study investigated whether this compound could constitute a threat signal that triggers defense and escape behaviors in humans.
How were the effects of the smell of death on humans tested?
The study used four experiments to test this:
Experiment 1 examined the effect of putrescine on vigilance. The participants were randomly divided into three groups: exposed to putrescine, ammonia or water, with the odors applied to cotton swabs one hour before the start of the test. Participants then had a reaction test on the computer, being instructed to click on a red dot as quickly as possible.
Experiment 2 investigated the influence of putrescine on escape behavior. Participants were exposed to one of three odor conditions (putrescine, ammonia, or water) and then asked to walk a distance of 80 meters to see how and if the time required varied.
Experiment 3 examined escape-related behavior and thoughts. After being exposed to putrescine, ammonia, or water, participants were engaged in a word completion task (e.g., “b_nk” can be completed with bank, bonk, or bunk), followed by a 60-meter walk to monitor the time required.
Experiment 4 explored defensive behaviors and whether putrescine has an effect even when the odor cannot be consciously detected by the person. Participants were exposed to very low concentrations of putrescine and ammonia, after which they were asked to read an essay critical of Western values and answer questions about their feelings toward the essay’s author. Their willingness to escape was also assessed by how quickly they completed the last questionnaire.
What did the scientists discover?
The study found that exposure to putrescine increased participants’ alertness, even when they were unaware of the smell. Putrescine-exposed participants walked faster in escape trials and displayed more hostility and defensive behaviors than those in the other conditions. This suggests that putrescine could trigger fight-or-flight responses to help us survive in dangerous situations, although it’s not clear what specific threat it might signal.
“Overall, the findings indicate that even brief exposure to putrescine mobilizes threat management responses designed to deal with environmental threats,” the study authors concluded.
Future research will try to understand the exact nature of the threat that rot signals, whether microbial or otherwise.
The study was published in Frontiers in Psychology.
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Source: www.descopera.ro
