What compels a stalker to pick out a victim, follow or harass them, and continually contact them? And what gives the stalker the recklessness to continue to pursue that victim, despite the risk of being caught?

In men, it could come down to the beat of their heart, according to a new paper in the Journal of Interpersonal Violence.

The paper is the latest linking criminality to the involuntary nervous system.

Arousal theory is the backdrop: those who are less excitable, with slower-beating hearts, generally have less fear, seek stimulation through the pursuit of victims – and may exhibit more impulsive behaviors, according to the team at Sam Houston State University.

The male college students whose heart rate was one standard deviation or more below the mean heart rate had three times the odds of having stalked someone.

This suggests low resting heart rate and those patterns of criminal behavior are linked, according to Danielle Boisvert, director of criminal justice graduate programs at Sam Houston State University in Texas, one of the authors.

“Our findings suggest that while heart rate is generally found to be associated with aggression and antisocial behavior across the sexes, these associations may be sex specific when discussing stalking perpetration,” said Boisvert.

The scientists looked at 384 college students who answered a survey on behaviors which could be considered stalking. They had their heart rate monitored by a finger pulse oximeter during the questions and answers. They were asked whether they had followed or spied on someone, or communicated to an unwilling person, among other topics. (The targets included strangers, current or former significant others, or friends and acquaintances. But bill collectors, telephone solicitors, or salespeople did not count as “stalking” behavior).

Thirty-two of the 384 had engaged in what would be defined as stalking behavior: 15 females, and 17 males.

The low resting heart rate was significant among the males – but not the females, according to the data. (Female stalkers appear to have a different modus operandi, according to previous studies: they typically have less criminal and substance-abuse history, prefer to use phones instead of physical interaction to harass, and are more likely to desire intimacy with the victim).

The males did show the more-aggressive tendencies, including the in-person following of their target.

Another finding from the study: males with affection for the parents were much less likely to be stalkers.

But whatever the psychological mechanisms spurring the behaviors, the lower heart rate appears to be linked to them, they added.

“While replication is certainly needed before reaching any definitive conclusions, our preliminary results suggest autonomic nervous system dysfunction as measured by (low resting heart rate) may be an important correlate to consider when studying stalking , particularly for male stalkers,” they write.

“Future studies should consider the impact of interactions between biological and genetic risk factors with various environmental and social conditions on stalking,” they add.

But the theory of a calm predator finding victims to arouse themselves has been around for more than a decade, with some of the first studies appearing around the turn of the millennium.

Those previous studies have associated lower heart rates, and less arousal, as an impetus linked to criminality. One of the studies with the widest scope, published in the journal JAMA Psychiatry in 2015, found a statistically-significant correlation between low heart rates and criminality in a population of more than 700,000 Swedish men.