When a murderer is on the loose in your home and you're trying to communicate with someone else without talking, you can easily direct their attention anywhere by intently looking at them and then looking somewhere else—their gaze will soon follow. Turns out a dog will understand the exact same thing.
A study was done with infants' gazes and how they react and look at things depending on the adult's expression. They used a similar tactic with dogs, who watched video presentations of a human looking at one of two objects. The dogs' eyes and head were tracked with a tracker, and it turns out they have a much higher tendency to look at the same object a human did.
This is significant in the study of studying dogs' social skills and the study of inter-species communication.