Shades of emotion: what the addition of sunglasses or masks to faces reveals about the development of facial expression processing.

Three studies investigated developmental changes in facial expression processing, between 3 years-of-age and adulthood. For adults and older children, the addition of sunglasses to upright faces caused an equivalent decrement in performance to face inversion. However, younger children showed better classification of expressions of faces wearing sunglasses than children who saw the same faces un-occluded. When the mouth area was occluded with a mask, children under nine years showed no impairment in expression classification, relative to un-occluded faces. An early selective focus of attention on the eyes may be optimal for socialization, but mediate against accurate expression classification. The data support a model in which a threshold level of attentional control must be reached before children can develop adult-like configural processing skills and be flexible in their use of face- processing strategies.