• Psychopaths may have a different sense of smell to other people.
  • They may find it harder to distinguish between common smells like coffee and oranges.
  • This alone is not enough to diagnose a psychopath, but it could be one indicator if someone shows other signs of psychopathy, such as a lack of empathy.

Most people show some of the signs of psychopathy. It’s very likely you fall on the spectrum somewhere for personality traits like superficiality, narcissism, promiscuity, and callousness. But that doesn’t mean you’re a psychopath, because only about 1% of the population is.

To be diagnosed as a psychopath, there’s rigorous mental testing and behavioural analysis involved. Over the years studies have tried to piece together the puzzle, and have found that if you are friends with a lot of your exes, or like bitter tastes you might have a higher chance of being a psychopath.

One study from 2012, published in the journal Chemosensory Perception, found that psychopaths could also have a slightly different sense of smell to the rest of us.

The researchers asked 79 non-criminal psychopaths to answer questions, which put them on the psychopathy scale. Then their olfactory abilities – threshold, identification, and, discrimination – were measured.

Results showed that people with stronger psychopathic traits found it harder to distinguish between common smells like coffee, fish, and oranges.

The reason for this is not known, as more research needs to be done, but the authors of the study speculate that it could be something to do with part of the brain functioning less effectively in psychopaths.

Typically, psychopaths have lesser functionality of the frontal parts of their brains, which are the areas that help us make decisions, behave appropriately in social situations, and also process smells.

"Olfactory measures represent a potentially interesting marker for psychopathic traits, because performance expectancies are unclear in odour tests and may therefore be less susceptible to attempts to fake good or bad responses," the researchers wrote.

It's important to remember that a bad sense of smell can be brought on by other things too, such as Alzheimer's disease, or something less severe like a cold, so it's not a definite indicator of psychopathy. But if someone also shows other signs, like manipulation, or a lack of empathy, it could be one of many indicators a specialist may use to diagnose them.