I would tend to go with the smell theory, and dogs can likely associate the smell of the female hormones and pheromones that women give off with particular mannerims that they might have, and which the animals find pleasing or reassuring.
This is not as outlandish as it might sound on the surface. Certain breeds of dogs have been trained to sniff out particular types of cancers in humans, and can sometimes detect them well before more conventional methods can.
