Right hemisphere decline in the perception of emotion as a function of aging
The hypothesis that the right cerebral hemisphere declines more quickly than the left cerebral hemisphere in the normal aging process was tested in two studies using a facial recognition and a response time task. In Study 1, subjects (N=60) were asked to identify facial affect fram 50 standardized photographs of 5 affective categories: Happy, Neutral, Sad, Angry, and Fearful, and were asked to rate the intensity of each photograph. The results of the analysis indicate that the elderly group was significantly less accurate at identifying negative and neutral affective expressions than the younger group, with no significant differences seen between groups in the identification of positive affect. The results also indicate that the elderly rated the affective expressions as being significantly more intense than the younger group.
Study 2 (N=60) investigated response times for the recognition of the affective stimuli as 4 function of visual field of presentation and valence of the stimuli, using the same subject population. The results of this analysis reveal that the elderly show an increase in cerebral lateralization in comparison to the younger group. The elderly exhibited increased response times to negative affect presented to the left hemisphere. The results of this study also indicate that both groups had faster response times to positive affect, and that both groups had a response bias in favor of positive affect when neutral facial affective slides were presented to the left hemisphere.
The results are interpreted as partially supporting the right hemi-aging theory. The elderly showed a diminished ability to identify negative affect across both studies, suggestive of lowered right hemisphere functioning. However, the increased rather than decreased cerebral asymmetry in the response time task, and slower response times to negative affect presented to the left hemisphere are suggestive of bilateral changes in affective processing for the elderly. Overall, these findings suggest that the elderly have more difficulty processing negative affect, while their ability to process positive affect remains intact. This finding has implications for research using facial affective paradigms designed for use with younger subjects, and suggests the need for more studies of emotional aging processes in normal populations.