Wolf (<em>Canis lupus</em>) hybrids highlight the importance of human-directed play behavior during domestication of dogs (<em>Canis familiaris</em>).

The domestication of animals and plants offers an exceptional opportunity to study evolutionary adaptations. In particular, domesticated animals display several behavioral alterations, including increased sociability and decreased fearfulness and aggression, when compared with their wild ancestors. However, studies quantifying simultaneous changes in multiple behaviors during domestication are lacking. Moreover, the role of human-directed play behavior has been largely neglected when studying the domestication process. Here we address these issues by examining behavioral changes during the domestication of the dog (Canis familiaris) from the gray wolf (Canis lupus) using a standardized behavioral test applied to wolf hybrids and several dog breeds. Contrary to expectations, our study provides little support for collective behavioral alterations. Specifically, although we found that wolf hybrids were less playful and overall more fearful than dogs, we did not detect any differences in sociability or aggression between wolf hybrids and dog breeds. Instead, our results suggest that behavioral alterations during domestication do not necessarily occur in concert and point to an important, but previously overlooked, role of selection on play behavior directed at humans during the domestication of dogs. (PsycINFO Database Record (c) 2018 APA, all rights reserved)