Lateral biases of attention and perception during face processing : what is the impact of ageing?

• Main Author: Williams, Louise
• Published: University of Strathclyde 2015
• Subjects: 150
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.655495

Although faces are processed bilaterally it is widely accepted that the right hemisphere (RH) dominates for processing attributes such as gender and identity and the left hemisphere (LH) dominates for processing lip-reading. The processing of emotional expressions is somewhat more equivocal, but depending on the emotion being expressed is dominated by either the RH or LH. This hemispheric laterality results in perceptual judgements being biased to the contralateral side when facial decisions are made, and for eye movements to be biased to the contralateral side of the face too. In older adulthood, however, lateralized hemispheric dominance is predicted to reduce as additional recruitment of the non-dominant hemisphere is also required to maintain performance, and this may impact on a reduction in lateralization of perception and eye movements. Consequently, it would be anticipated that in older adulthood a reduction in hemispheric lateralization would impact on the lateralization of perceptual judgements and eye movements during face processing tasks. To test this, a series of experiments were devised to investigate differences in the perceptual and eye movement lateralization of younger and older adults when facial decisions are made. Four studies are reported; studies one and two investigated the RH dominant face processing tasks of gender and identity, study three investigated the LH dominant task of lip-reading and study four investigated emotion processing which, depending on the emotion expressed, is dominated by either the LH or RH. Studies three and four also used the Landmark task to assess whether lateral response biases are face specific. The results of these studies provide empirical evidence quantifying the impact of ageing on lateralized judgements and eye movements using tasks associated with predominantly unilateral processing in younger adulthood. Differences according to age are discussed in relation to cortical changes and the predictions of theories of ageing.