抄録
Recent studies with non-human primates have found eye preferences consistent with the valence model of emotional processing, which states that the left hemisphere of the brain is dominant for processing positive emotion and the right hemisphere is dominant for processing negative emotion. This behavioural asymmetry could potentially be used as a welfare measure. The study explored whether capuchin monkey eye preferences differ systematically in response to stimuli of both positive and negative valence. 11 captive capuchin monkeys were presented with four images of different emotional valence and social relevance, and eye preferences for viewing the stimuli through a monocular viewing hole were recorded. A right eye preference (left hemisphere dominance) was predicted for viewing stimuli of positive valence and a left eye preference (right hemisphere dominance) was predicted for viewing stimuli of negative valence. An individual level eye preference was found; seven subjects had a strong left eye preference (right hemisphere dominance) and four subjects had a strong right eye preference (left hemisphere dominance) for viewing all the stimuli. The direction of looking did not differ significantly with the emotional valence of the stimuli and so the results do not support the valence model. The number of looks, duration of looking and latency between looks also did not differ significantly with the emotional valence of the stimuli. The stimuli were presented as images rather than real objects which may have reduced their emotional salience. However, significantly more stress-related behaviours were found for viewing the negatively than positively valenced stimuli, suggesting the stimuli had a degree of emotional relevance for the subjects. In conclusion the findings of this study do not provide convincing support for eye preferences as a measure of emotional responses in captive capuchin monkeys and therefore its potential as a welfare measure in non-human primates is still ambiguous.
