The human-dependent behavior of dogs is influenced by multilevel evolutionary and environmental factors

Reliance on humans in problem-solving situations, and the reaction to the absence of the owner, are commonly used ethological paradigms that investigate human-dependence in dogs. For the first time, we investigated the combined effect of three influencing factors. Two of these factors are related to artificial selection: functional selection resulted in cooperative and independent working breeds, and more recently, selection for working and show lines caused within-breed divisions. The third factor was whether dogs were engaged in regular sports activity. We tested N = 137 purebred dogs (from 49 breeds) in both the “unsolvable task” and an indoor separation test. We found that cooperative dogs showed more dependent behaviors in the “unsolvable task” than the independent breeds did. Breeding lines also had a strong modifying effect, as the working-line dogs showed weaker human-dependency than dogs from show lines. Sports engagement could also mask the influence of the breeding lines: in show lines sports, engagement came with lower human-dependency but with increased reliance on humans from working line dogs. In the separation test, all three factors were in association with dogs’ reactions: whining, a sign of fear, was more prevalent in the show-line dogs, and barking, a sign of frustration, was high in both sport-involved independent breeds, and non-working cooperative breeds. We conclude that dependency is a universal trait in dogs that has been primarily determined by two levels of selection: functional breed selection and breeding lines, but this can be further modified by lifetime experiences, such as training/sports activity.