What Facial Part Is Important for Japanese Monkeys ( ) in Recognition of Smiling and Sad Faces of Humans ( )?
AbstractFour Japanese monkeys ( ) and 17 humans ( ) performed an odd-item visual search task of a variety of photos of human facial expressions. The target was either a genuine smiling face or a sad face of a female. The distracters were the following artificial images produced by a computerized image processing system: (a) a neutral face made by averaging the 2 targets or (b) faces with smiling or sad eyebrows, eyes, cheeks, or mouth on the neutral face. The search reaction time of both species was the longest when they had to find the smiling target among the distracters having the smiling cheeks. In searching for the sad target, however, the reaction time of humans was the longest when the distracters had sad eyebrows or sad cheeks, whereas the longest reaction time for monkeys was when the distracters had sad cheeks. These results indicate that monkeys search smiling human faces as humans do, but monkeys do not use eyebrows as a cue to search sad human faces.