Judgements of facial and vocal signs of emotion in infants with Down syndrome

We address how adults perceive facial and vocal signs of emotions in infants with and without Down syndrome. A set of naturalistic data from infants with trisomy 21 and typically developing infants (joy expression of young infants, 3.8-4.4 months, and anger and neutral expressions of older infants, 6.8-12.8 months) was rated by adult judges categorically or dimensionally. Facial signs alone, vocal signs alone, and both facial and vocal signs were presented for each expression. Raters were university students who did not have regular contact with infants, nor with people with mental retardation. Young infants' joy expressions were correctly recognized more frequently for typically developing infants than for infants with Down syndrome and, specifically, joy vocalizations in infants with Down syndrome were not identified. Facial signs were also more communicative than vocal signs in the case of older infants' anger and neutral expressions. These results are relevant to the way infant emotion is perceived by others, and may be particularly useful in facilitating interaction between adults and infants with Down syndrome.