It's obvious dogs have learned some of our language. Now it's our turn to learn dog language."" But despite the title and introductory promise, and despite Fox's similar service to adults in Understanding Your Dog (1972), this simple questionand-answer session is as much an all-round dog owners' advisory as it is an interpretation of Fido's body language. To start, Fox explains how to read the different puppies' behavior in selecting from a litter, suggests tests for muscle control, temperament, etc., and, more conventionally, includes a chart checking off characteristics (size, aggressiveness, care required) for different breeds. His lead-in questions are sometimes unabashed setups for generalized minilectures (""All right, what is dominance hierarchy?""), sometimes efforts to anticipate childrens' queries (""What happens when a dog is 'put away'?""), and now and then they bear directly on the stated focus of the book: ""Is my dog really smiling at Uncle Geoffrey? . . . Why does our German shepherd bark and crouch at crippled people? . . . When I come home my five-month-old Dalmatian barks and bows. What does he mean?"" Drawings and photos of expressive postures extend the theme, and there's no doubt that Dr. Fox has the answers. But this hasn't the muscle we've come to expect from him, and other juveniles have already digested his research.