I don't know about any research on doggy sighs, but there's a serious biological and philosophical literature on the canid play bow, "a highly ritualized and stereotyped movement that seems to function to stimulate recipients to engage (or to continue to engage) in social play." It was first studied by ethologist Marc Bekoff in the 1970s, and was featured in philosopher Ruth Millikan's 1984 work Language, Thought and other Biological Categories. The Cogprints archive includes a 1997 chapter by Bekoff and philosopher Colin Allen, Intentional Communication and Social Play: How and Why Animals Negotiate and Agree to Play.
Here's a quote from the Bekoff and Allen chapter that may help to explain why this is serious stuff:
From the intentional stance, if a believes that b believes that a desires to play (third-order) it would seem that ideal rationality would also require that a believes that b has a belief (second-order). But from a Millikanian perspective this more general second-order belief, if it requires a to have a general belief detector, may actually be more sophisticated than the third-order belief which supposedly entails it. A general belief detector may be much more difficult to evolve than a specific belief detector, for the detection of specific beliefs may be accomplished by the detection of correspondingly specific cues.
If this is correct, then on Millikan's account Jethro (Marc's dog) may be capable of the third-order belief that (or, at least, a state with the intentional content that) Sukie (Jethro's favorite canid play pal) wants Jethro to believe that her bite was playful not aggressive, even though Jethro is perhaps limited in his ability to represent and hence think about Sukie's second-order desires in general.
Linguists who work on Gricean accounts of what people mean by what they say should think more carefully about the analogous issues, though for our species, evolved cultural norms may be just as important as evolved biological systems.
I've observed, in an entirely unscientific way, that the canid play bow causes friction between domestic dogs and cats who may otherwise get along very well, since cats don't understand it, and dogs don't understand that cats don't understand it. I've had relationships like that -- haven't you?
Posted by Mark Liberman at January 16, 2004 09:24 PM