Eye contact effects on social preference and face recognition in normal ageing and in Alzheimer's disease.

Perceiving a direct gaze (i.e. another individual's gaze directed to the observer leading to eye contact) influences positively a wide range of cognitive processes. In particular, direct gaze perception is known to stimulate memory for other's faces and to increase their likeability. Alzheimer's disease (AD) results in social withdrawal and cognitive decline. However, patients show preserved eye contact behaviours until the middle stage of the disease. The eye contact effects could be preserved in AD and be used to compensate for cognitive and social deficits. Yet, it is unknown whether these effects are preserved in normal ageing. The aim of this study was to address whether the positive effects of eye contact on memory for faces and likeability of others are preserved in healthy older adults and in patients with early to mild AD. Nineteen AD patients, 20 older adults and 20 young adults participated in our study. Participants were first presented with faces displaying either direct or averted gaze and rated each face's degree of likeability. They were then asked to identify the faces they had previously seen during a surprise recognition test. Results showed that the effect of eye contact on other's likeability was preserved in normal ageing and in AD. By contrast, an effect of eye contact on memory for faces seems to emerge only in young participants, suggesting that this effect declines with ageing. Interestingly, however, AD patients show a positive correlation between ratings of likeability and recognition scores, suggesting that they implicitly allocated their encoding resources to most likeable faces. These results open a new way for a "compensating" therapy in AD.