Eyeing the eyes in social scenes: Evidence for top-down control of stimulus selection in simultanagnosia

Abstract

Simultanagnosia is a disorder of visual attention resulting from bilateral parieto-occipital lesions. Healthy individuals look at eyes to infer people's attentional states, but simultanagnosics allocate abnormally few fixations to eyes in scenes. It is unclear why simultanagnosics fail to fixate eyes, but it might reflect that they are (a) unable to locate and fixate them, or (b) do not prioritize attentional states. We compared eye movements of simultanagnosic G.B. to those of healthy subjects viewing scenes normally or through a restricted window of vision. They described scenes and explicitly inferred attentional states of people in scenes. G.B. and subjects viewing scenes through a restricted window made few fixations on eyes when describing scenes, yet increased fixations on eyes when inferring attention. Thus G.B. understands that eyes are important for inferring attentional states and can exert top-down control to seek out and process the gaze of others when attentional states are of interest.

Keywords:

• Attention
• Eye gaze
• Neuropsychology
• Simultanagnosia
• Social scenes perception

Acknowledgments

K.A.D. and E.B. were supported by the Natural Sciences and Engineering Research Council (NSERC), and the Michael Smith Foundation for Health Research (MSFHR). A.K. was supported by NSERC, a MSFHR Senior Scholar award, the Human Early Learning Partnership, and the Hampton Foundation. J.J.S.B. was supported by a Canada Research Chair and MSFHR Senior Scholarship. W.F.B. was supported by NSERC. Thank you to G.B. for his time and dedication to this project.

Notes

¹ The importance of replication has never been more important in the field of cognitive and social neuroscience, a point that has recently been driven home in the Special Issue of the Perspectives on Psychological Science (2012) Volume 7, Number 6.

² The present finding is especially remarkable because the gaze-contingent group consisted of young controls (mean age 25.6 years), demonstrating that visual restriction, and not age, is the critical factor. We have previously shown that the fixation behaviour of healthy individuals who were matched in age to the simultanagnosic patient S.L. (49 years) did not differ from the fixation behaviour of a group of young controls (mean age 22 years), further suggesting that age is not critical to our results (Dalrymple et al., 2011a).