Selective eye fixations and misinterpretation of non-happy eyes in smiling faces

Abstract There is a wide variety of smiles, and not all of them convey genuine happiness. We investigated how a smiling mouth in blended facial expressions with non-happy eyes (neutral, surprised, sad, fearful, disgusted, or angry) can wrongly bias their judgement as “happy” and slow down their correct evaluation as “not happy”. The attentional focus of participants was initially cued to the mouth of face stimuli, followed by unrestrained free viewing, with online assessment of eye movements. The face eye region was either congruent with the mouth (same eye-mouth expression), incongruent (non-happy eyes and a smile), or unrelated (no-mouth control). Results revealed: (1) interference in the incongruent condition, with non-happy eyes being incorrectly judged as “happy” and slowly judged as “not happy”; (2) the eyes, but not the mouth, were looked at longer and more often when they were incongruent; and (3) both effects varied depending on the type of non-happy eye expression. These findings are discussed in terms of two properties of the smiling mouth: (a) visual saliency driving an early perceptual-overshadowing/inattentional-blindness mechanism, and (b) diagnostic value driving a later semantic/categorical-priming mechanism. They presumably underlie the biasing influence of a smile on non-happy eyes in blended facial expressions.