Puppies don't learn how to communicate with humans; rather, it's likely they are born knowing how to respond to our gestures and vocal cues after years of advantageous genetic selection during the domestication process, according to a new study published Thursday.
By showing that 8-week-old puppies seem primed to receive human communication through heritable social-cognitive traits, the study, published in Current Biology, provides new insight into the development of domesticated dogs and offers new information that can be taken into account in future dog-breeding decisions.
"Behaviors like eye contact and ability to understand socially conveyed information are at the crux of the human-animal bond, and this study shows that these behaviors are largely influenced by the genetics of the individual dogs," said lead author Emily Bray, a postdoctoral researcher of animal cognition at the University of Arizona and at Canine Companions for Independence, a nonprofit that trains and provides service dogs at no cost to people with disabilities.
Unlike apes and other intelligent animals that are more closely related to humans, dogs are particularly good at responding to cooperative communication from humans, such as pointing gestures. According to Bray, the desire to understand where this sensitivity came from and whether it was selected and inherited through genetics or learned through experience with humans helped motivate the study.
To test the potential genetic root of social communication in dogs, Bray and her colleagues conducted a battery of cognition tests on 375 8-week-old service-dog candidate puppies. Knowing that these dogs, all about the same age, descended from a known pedigree and testing all of the puppies in the same standardized way on the same tasks allowed the research team to create a statistical model that could indicate the genetic heritability of the skills being tested.
These tests included a number of hiding-finding warm-ups, or exercises where researchers assessed the puppies' interest in finding food under cups or in various locations on a training mat, as well as human-interest tasks, where a researcher would repeat a standardized script to a puppy, as if talking to an infant, and then time how long the puppy looked at them, as well as how long the puppy spent at arm's length from the researcher once they entered the test space.
The study also included gesture-following tasks, where, for example, a researcher gave a puppy a piece of kibble and then showed the puppy two plastic cups spaced apart, with one containing a piece of kibble. The researcher then pointed to the reward cup, exclaiming, "Puppy, look!" and watched to see whether the puppy moved toward it.
During some of these tasks, the team found that puppies were able to follow points on their very first try, with no subsequent improvement on later attempts. According to Bray, this suggests that puppies are pre-equipped with the abilities to carry out the tasks successfully.
Using their statistical model, Bray and her colleagues determined that genetic factors accounted for 43% of the puppies' variation in their ability to follow the point-following task. Naturally, individuals perform differently from one another, according to a wide range of factors outside of genetics, including environment, nutrition, experience and more. When 43% of variation in ability can be attributed to genetics, it is likely a desirable and heritable trait.
"These are quite high numbers, much the same as estimates of the heritability of intelligence in our own species," Bray told The Academic Times.
"Even with just your run-of-the-mill companion dog, these abilities help foster attachment (we know mutual eye gaze increases oxytocin levels in both species) and strengthen our human-animal bond," Bray said. "Thus, ancient dogs who displayed these skills, especially by weaning age, were likely at a selective advantage."
Identifying the heritability of social-communicative skills in dogs now allows for further research into the genetics that govern these traits. To that end, Bray and her colleagues are conducting preliminary research, collecting blood samples and cognitive data from adult dogs, for a future genome-wide association study to find the genetic markers that identify dogs' attunement to human communication.
However, Bray says that genetics alone do not influence communication, though they do play a significant role. In another forthcoming study, Bray and her colleagues are examining 60 litters to assess how maternal styles over the first three weeks of life may influence cognition later on.
The study, "Early-emerging and highly heritable sensitivity to human communication in dogs," published June 3 in Current Biology, was authored by Emily E. Bray, University of Arizona and Canine Companions for Independence; Gitanjali E. Gnanadesikan, Daniel J. Horschler and Evan L. MacLean, University of Arizona; Kerinne M. Levy and Brenda S. Kennedy, Canine Companions for Independence; Thomas R. Famula, University of California, Davis.