we are also grateful to darby proctor for useful comments on a previous version of the manuscript .
the present study was approved by the ethics committee of azabu university ( japan ) ( no .
1303042 ) . this research was supported by the jsps research fellowships for foreign researchers ( no .
p10311 ) and the mext grant - in - aid for scientific research ( no .
26380981 ) to t. r. , the mext grant - in - aid for challenging exploratory research ( no .
23650132 ) to t. h. , and the grant - in - aid for scientific research on innovative areas ( no .
 in a recent paper,1 we examined whether oxytocin in the domestic dog modulates the maintenance of close social bonds in non - reproductive contexts . we found that exogenous oxytocin promotes positive social behaviors not only toward conspecifics , but also toward human partners . 
 here we examined in further detail the effect that oxytocin manipulation has on social play . when sprayed with oxytocin , 
 subjects initiated play sessions more often and played for longer periods of time than when sprayed with saline . furthermore , after oxytocin nasal intake dogs displayed play signals more often than after saline administration , suggesting that oxytocin enhances dogs ' play motivation . to our knowledge 
 , this study provides the first evidence that oxytocin promotes social play in the domestic dog . 
 we use these results to hypothesize on the potential therapeutic use of oxytocin for promoting social behaviors and treating social deficits in the domestic dog . 