Those with weaker bonds were separated from those with stronger bonds to their pets. The owners were instructed to sit in a room with their dogs and simply make eye contact or talk to, not pet the animals. Those who reported stronger bonds with their dogs saw theirs – and their dogs' – levels of oxytocin rise. And the longer those dogs who were more strongly bonded gazed at their humans, the more oxytocin they produced, leading researchers to believe that those sweet, gazing expressions on dogs' faces mean more than you might think – they really are a look of love. Another study found that there was no discernible increase in oxytocin with cats vs. dogs. But those who had owned mostly cats throughout their lives seemed to have less of an overall jump in oxytocin. Dog owners seem to be "trained" to expect that bond.