The smell of rotten fish is detected before the smell of roses

Without a doubt, roses smell better than rotten fish, but the brain detects the smell of the latter with more speed and precision , according to a study by American and Canadian scientists and published in the journal Biological Psychology .

"The olfactory system reacts earlier to stimuli that pose a danger ", explains Johannes Frasnelli, co-author of the work. According to the researcher, it had already been shown that "the human brain detects an aggressive facial expression faster than a smiling face, because an angry face is a potential enemy ready to attack." Frasnelli wondered if the same was true of odorous stimuli. Comparing the brain response of various subjects to pleasant and unpleasant odors emitted by food (oranges and rotten fish) and other objects (roses and dirty socks), he and his colleagues showed that the response time to the stench of spoiled fish was of 1,300 milliseconds, while for the rest of the smells it amounted to 1,700 milliseconds.

As scientists conclude, it is a matter of natural selection, which has made us retain the abilities that help us to more quickly identify threats, in this case food that can make us sick or even kill us.