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Claire A Conway, Benedict C Jones, Anthony C Little, Lisa M DeBruine, Arash Sahraie; Transient pupil constrictions when viewing human and macaque faces. Journal of Vision 2007;7(9):631. doi: 10.1167/7.9.631.
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© ARVO (1962-2015); The Authors (2016-present)
While it is well established that there are rapid transient constrictions of the pupil in response to various low-level aspects of visual stimuli that are processed along the ventral and dorsal pathways (e.g. light flux, colour, gratings and motion), we know of no previous studies that have demonstrated rapid transient pupil constrictions to more complex visual stimuli. Since the neural mechanisms that underpin face perception occur further along the ventral pathway than those that underpin colour processing, one would expect the presence of a transient pupil constriction when viewing faces. The response latencies may also be expected to be similar or larger than those elicited by coloured targets, reflecting activity further along the visual pathways. Here we present evidence from three experiments of a transient pupil constriction elicited by the onset of face stimuli, with a typical latency of approximately 360ms. The response amplitudes are significantly smaller for scrambled or inverted face stimuli. This suggests that the pupil response is associated with configural processing that occurs to a greater extent when processing upright faces than when processing other types of visual stimuli. Furthermore, the effect of inversion on the transient pupil constriction was smaller when stimuli were macaque faces than when stimuli were human faces, suggesting that the pupil response is also influenced by familiarity with the category of face shown. These findings are consistent with the pupil response to faces being influenced by neural mechanisms along the ventral pathway that are important for face processing (e.g. the fusiform face area), and reveal a novel, objective and non-invasive method for studying face perception.
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