What Pleasure Looks Like in Babies, Primates and Rats

To decipher the brain circuits that underlie pleasure, neuroscientists often have to assess liking and disliking in nonverbal creatures. They do it by monitoring facial expressions and head and arm movements, such as those depicted in the video here. Licking the lips, for instance, indicates a food tasted delicious to in infant, whereas turning the head from side to side indicates “yuk.” In the video, the term “hedonic reactions” refers to pleasure.