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How “puppydog eyes” do their trick: chemistry

Jan. 13, 2009
Special to World Science  

If you’ve ev­er won­dered how just one dole­ful look from your dog al­ways makes you for­give that chewed-up shoe—or al­most an­y­thing else—sci­en­tists may have an an­swer.

A dog’s gaze trig­gers re­lease of the so-called “trust hor­mone” ox­y­to­cin in own­ers, ac­cord­ing to Jap­a­nese re­search­ers.

A dog’s gaze trig­gers re­lease of the so-called “trust hor­mone” ox­y­to­cin in own­ers, ac­cord­ing to Jap­a­nese re­search­ers. Ox­y­to­cin, pro­duced by the pi­tu­i­tary gland at the base of the brain, is im­pli­cat­ed in bond­ing be­hav­iors in an­i­mals in­clud­ing hu­mans. (Im­age cour­tesy Frank­lin County Dog Shel­ter, Ohio)
Ox­y­to­cin, pro­duced by the pi­tu­i­tary gland at the base of the brain, has been im­pli­cat­ed in bond­ing be­hav­iors in an­i­mals in­clud­ing hu­mans. Ex­pe­ri­ments have even found that sniff­ing ox­y­to­cin in­creases a per­son’s trust­ful­ness of others.

In a new study, Mi­no Na­ga­sawa of Az­abu Uni­ver­s­ity in Ja­pan and col­leagues placed dog own­ers to­geth­er with their pets in a se­ries of half-hour ses­sions.

The ex­pe­ri­menters meas­ured the lev­els of ox­y­to­cin in own­ers’ urine be­fore and af­ter the in­ter­ac­tions.

The investigators found in­creases in the hor­mone lev­el that were highly cor­re­lat­ed to “the fre­quen­cy of be­hav­ior­al ex­changes in­i­ti­at­ed by the dog’s gaze,” they re­ported, writ­ing in the Dec. 14 is­sue of the re­search jour­nal Hor­mones and Be­hav­ior.

The re­search­ers ar­ranged an­oth­er set of ex­pe­ri­ments that were sim­i­lar, ex­cept that own­ers were in­structed not to look at their pooch dur­ing the in­ter­ac­tions. In these tests, the ox­y­to­cin-gaze cor­rela­t­ion was­n’t found, the sci­en­tists re­ported.

In the past, it has­n’t been clear wheth­er ox­y­to­cin is linked to bond­ing be­tween dif­fer­ent spe­cies, wrote Na­ga­sawa and col­leagues. “We con­clude that in­ter­ac­tions with dogs, es­pe­cially those in­i­ti­at­ed by the dog’s gaze, can in­crease the uri­nary [ox­y­to­cin] con­centra­t­ions of their own­ers as a man­i­festa­t­ion of at­tach­ment be­hav­ior.”

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If you’ve ever wondered how just one doleful look from your dog always makes you forgive that chewed-up shoe—or almost anything else—scientists may have an answer. A dog’s gaze triggers release of the so-called “trust hormone” oxytocin in owners, according to Japanese researchers. Oxytocin, produced by the pituitary gland at the base, is implicated in bonding behaviors in animals including humans. Experiments have found that sniffing oxytocin increases a person’s trustfulness during a social interaction. Mino Nagasawa of Azabu University in Japan and colleagues placed dog owners together with their pets in a series of experiments in which researchers observed the pet-owner interactions for 30 minutes. The experimenters also measured the concentration of oxytocin in owners’ urine before and after the interactions. The increase in the hormone level was highly correlated to “the frequency of behavioral exchanges initiated by the dog’s gaze,” the investigators reported, writing in the Dec. 14 issue of the research journal Hormones and Behavior. The researchers arranged another set of experiments that were similar, except that owners were instructed not to look at their pooch during the interactions. In these tests, the oxytocin correlation wasn’t found, the scientists reported. In the past, it hasn’t been clear whether oxytocin is linked to “inter-species social bonding,” wrote Nagasawa and colleagues. “We conclude that interactions with dogs, especially those initiated by the dog’s gaze, can increase the urinary [oxytocin] concentrations of their owners as a manifestation of attachment behavior.”