Inside of a Dog: What Dogs See, Smell, and Know

by Alexandra Horowitz

dogs pick up on our hormonal levels in interaction with them. Looking at owners and dogs participating in agility trials, the researchers found a correlation between two hormones: the men’s testosterone levels, and the dogs’ cortisol levels. Cortisol is a stress hormone—useful for mobilizing your response to, say, flee from that ravenous lion—but also produced in conditions that are more psychologically than mortally urgent. Increases in the level of the hormone testosterone accompany many potent elements of behavior: sex drive, aggression, dominance displays. The higher the men’s pre-agility-competition hormonal levels, the higher the increase in the level of stress in the dogs (if the team lost). In a sense, the dogs somehow knew that their owner’s hormonal level was high, by observing behavior or through scent or both—and they “caught” the emotion themselves. In another study, dogs’ cortisol levels revealed that they were even sensitive to the style of play of human playmates. Those dogs playing with people who used commands during play—telling the dog to sit, lie down, or listen—wound up with higher postplay cortisol levels; those playing with people who played more freely and with enthusiasm had lower cortisol at play’s end. Dogs know, and are infected by, our intent, even in play.