Nice dogs finish last. That statement does not refer to racing (or dating), however, but rather to the recent finding that agreeable, trainable dogs live longer than other, more aggressive dogs.

A study from researchers at Quebec’s Sherbrooke University suggests that “artificial selection on dogs (through domestication) generated variations in personality traits that are correlated with life histories and metabolism.”

The scientists found that dogs that are more obedient on average live longer than disobedient or bold dogs, and more aggressive breeds have higher energy needs than nonaggressive breeds. Lead researcher Vincent Careau, a PhD student at Sherbrooke University, said there was a link between personality and longevity, but it was not what most people think.

“What can be said from the results is that personality and the ‘pace-of-life’ (longevity, metabolic rate) may be co-evolving together through natural selection and/or artificial selection,” Careau said. “Ironically, what cannot be said from the results is what most people tend to interpret: that if you train your dog to be obedient it will live longer.”

He pointed out that the results are not about individual dogs, but rather the averages for different breeds. For example, the chart below compares two pairs of breeds with similar body mass but different trainability scores.

The personality scores are based on a 1995 study by Thomas Draper, “Canine Analogs of Human Personality Factors.” In Draper’s study, he scored different breeds according to three factors: Reactivity-surgency; Aggression-disagreeableness; and Trainability-openness.

Careau noted that the connection between longevity and trainability and the connection between aggressiveness and metabolizable energy intake (MEI) are “correlated responses.” In other words, the longevity of different breeds was affected indirectly as a result of human’s selectively breeding dogs for certain personalities.

“Humans selected for morphology and behavior, probably not for longevity and energy needs. So the correlations we observed are likely the result of a correlated response,” Careau said. “In front of these results, we cannot tell the direction of the causality. It could be that breeds that are ‘genetically programmed’ to die if they are bolder and disobedient, since they have less to lose. It could also be that obedient and trainable breeds are less likely to being hit by a car when crossing the street.”

The study, “The pace of life under artificial selection: personality, energy expenditure, and longevity are correlated in domestic dogs,” was published in The American Naturalist.