Many studies have studied the behavior of dogs and their connections to people but not all attempt to explain the genetic basis for this behavior.

A new study published on July 19 in the online journal Science Advances suggests that it has located one genetic marker that reveals hypersociability in dogs. Using the genetic markers in people who have Williams-Beuren syndrome (WBS), a genetic disorder that makes friendly and trusting, researchers found the same marker in dogs showing that they had variations in the same kinds of genes that wolves did not possess.

Researchers noted that dogs continue to display hypersociability into adulthood and set them apart from wolves, even wolves who have been hand-raised by people. The study described hypersociability as “a multifaceted phenotype that includes extended proximity seeking and gaze, heightened oxytocin levels, and inhibition of independent problem-solving behavior in the presence of humans.”

Before analyzing the genomic reason on chromosome 6, the researchers evaluated the human-directed sociability of 18 domestic dogs and 10 captive human-socialized gray wolves. They did this by giving the dogs and wolves problem-solving tasks and assessed three behaviors that are indicative of WBS: attentional bias to social stimuli, hypersociability, and social interest in strangers.

Overall, dogs spent a greater amount of time gazing at humans and sought proximity to people more than wolves did. By developing an idea of the sociability of the dogs and wolves, researchers could then determine whether the genetic findings had any relation to their behavior.

They identified and resequenced a candidate locus associated with WBS in humans and known to be under positive selection in the domestic dog genome. The study revealed a statistically significant association between structural variations in GTF2I and GTF2IRD1 with measures of human-directed social behavior typical of WBS. Patients with intact GTF2I and GTF2IRD1 did not exhibit hypersociability. They also discovered of the two structural variations most associated with hypersociability in domestic dogs but not wolves.

As a result, the study proposes that one aspect of domestication is that individuals with hypersocial tendencies were favored under selective breeding leading to adult dogs that show exaggerated motivation to seek social contact unlike adult wolves. This study provides insight into one genetic mechanism that was shaped by selection during species domestication and points to a biological reason for dogs’ hypersociability.

Photo credit: © iStock/Michael Krinke