Smiling at a dog could have a similar effect on its brain to food, praise, or seeing someone familiar, according to a new study. Researchers at the University of Vienna found that dogs showed increased activity in a reward-related area of the brain when they were shown happy human faces. The study tested 14 dogs using brain scans while they viewed people displaying different emotions. The researchers found that positive expressions produced a distinct response that was not triggered by anger, fear, or sadness. Article continues after adPexels Smiling at dogs is rewarding for them“So this finding suggests that happy faces, even those of strangers, have a positive value for dogs,” she told the BBC.