In a supposedly groundbreaking study, Gregory Berns at Emory University has taken brain scans of dogs that were fully awake to try to figure out what they're thinking. MRIs measured the dogs' responses to human signals:
In the first experiment, the dogs were trained to respond to hand signals. One signal meant the dog would receive a hot dog treat, and another signal meant it would not receive one. The caudate region of the brain, associated with rewards in humans, showed activation in both dogs when they saw the signal for the treat, but not for the no-treat signal.
But as any dog owner knows, of course their pets know what behavior will be rewarded with treats ... if dogs could talk, they'd be telling us this study was a waste of time and money.