You might think that your brain processes the colon and parenthesis that form an emoticon smiley face in the same way it understands human facial cues, but you'd be wrong. Turns out, your mind understands the emotion, but doesn't confuse it with a face.
In one study from the University of Japan, participants were shown happy (^_^) and sad (T_T) emoticons, along with pictures of human faces expressing the same emotions. A scan revealed that the emotional processing area of the brain was activated in both cases, but only when participants looked at actual humans did their brains' face-processing regions light up, too.
Another study found more of the same, but this time linked emoticon comprehension with an area of the brain responsible for understanding text.
Surprised? You shouldn't be. The theory is that emoticons fall somewhere in between pictures and words — and that's exactly what they are. (Co.Design)