Animals and human body movements
Chapter 12 endnote 37, from Lisa Feldman Barrett.
Some context is:
Unfortunately, the experimenters did not test to see if the owners were behaving differently in the three conditions (toy dog, jack-o-lantern, and reading) in any way that could account for the dogs’ behavior. They assumed that the owner’s behavior was identical, and that the dog understood that jealously was called for in only one condition. [...] An owner’s subtle movements can have a large effect on an animal’s behavior (due to statistical learning.
The interesting research by psychologist József Topál and colleagues shows that dogs are exceedingly sensitive to human body movements, including eye gaze.
A classic example of humans inadvertently cueing animals can be found in the horse named Clever Hans, who appeared to solve complex mathematics problems on his own, by tapping his hoof. Scientists discovered that Hans was attending to subtle body motions made unwittingly by his owner. (When the owner was absent, Hans’s mathematical abilities vanished.)