Recognition of emotion in facial expression by people with Prader-Willi syndrome

People with Prader-Willi syndrome (PWS) may have mild intellectual impairments but less is known about their social cognition. Most parents/carers report that people with PWS do not have normal peer relationships, although some have older or younger friends. Two specific aspects of social cognition are being able to recognise other people's emotion and to then respond appropriately. In a previous study, mothers/carers thought that 26% of children and 23% of adults with PWS would not respond to others' feelings. They also thought that 64% could recognise happiness, sadness, anger and fear and a further 30% could recognise happiness and sadness. However, reports of emotion recognition and response to emotion were partially dissociated. It was therefore decided to test facial emotion recognition directly.

The participants were 58 people of all ages with PWS. They were shown a total of 20 faces, each depicting one of the six basic emotions and asked to say what they thought that person was feeling. The faces were shown one at a time in random order and each was accompanied by a reminder of the six basic emotions.

This cohort of people with PWS correctly identified 55% of the different facial emotions. These included 90% of happy faces, 55% each of sad and surprised faces, 43% of disgusted faces, 40% of angry faces and 37% of fearful faces. Genetic subtype differences were found only in the predictors of recognition scores, not in the scores themselves. Selective impairment was found in fear recognition for those with PWS who had had a depressive illness and in anger recognition for those with PWS who had had a psychotic illness.

The inability to read facial expressions of emotion is a deficit in social cognition apparent in people with PWS. This may be a contributing factor in their difficulties with peer relationships.