In not the most reassuring study we have ever read, psychologists from Berlin and Hamburg, Germany, have found that people with psychopathic and sadistic traits are more likely to have an interest in fire.

The team wanted to investigate the relationship between the "dark tetrad" of personality traits – Machiavellianism, psychopathy, narcissism and sadism – and an interest in fire, and setting fires.

"Fire setting is a significant problem for society, costing many human lives and causing great property damage," the team write in their study, citing wildfires and the burning of Notre-Dame. 

"One important risk factor of fire setting observed in forensic samples is fire interest. However, less is known about the relationship of fire interest and fire setting to other variables such as personality traits in subclinical samples."

The team recruited 222 students to participate in the study, and assessed them on dark tetrad traits. As well as this, they assessed the subjects' interest in fire and setting fires. Participants were asked to rate how much they liked fire-based activities such as “watching an ordinary coal fire in an ordinary house" and "seeing a hotel on fire on the TV news" on a scale from "absolutely horrible or most upsetting possible" to "lovely, very exciting, or very nice".

The team, based on earlier studies, suspected that traits associated with psychopaths (such as thrill-seeking and impulsivity) might be associated with an increased interest in fire. Sure enough, the results showed a positive correlation between psychopathic traits and interest in setting and watching fires.

"Our results for psychopathy provide further evidence for the close relation of impulsivity and fire setting," the team wrote in their discussion. "Psychopathy showed the strongest relation of the three Dark Triad traits [Machiavellianism, psychopathy and narcissism] to fire interest and fire setting."

Sadism was also positively correlated with an interest in fire and fire setting. However, there was a difference between the types of sadists; physical or direct sadists (who enjoy inflicting cruelty) and vicarious sadists (people who enjoy watching cruelty).

"We found higher correlations of physical and vicarious sadism with fire interest compared to fire setting," the team wrote. "For vicarious sadism, where the difference showed itself most clearly, this could be explained by the fact that watching a fire may already satisfy sadistic needs...while the act of setting the fire is of less importance."

“The other constructs of the Dark Tetrad and sensation seeking do not seem to play an important role in the prediction of fire setting and fire interest beyond psychopathy and sadism," they added.

The study was published in Frontiers In Psychology.