Contrast orientation and recognition of facial identity across variable lighting conditions
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1
University of Queensland, School of Psychology, Australia
Faces are three dimensional structures whose shading is responsible for much of the contrast in facial images. This shading is usually generated by a light source located above the observer and facial recognition is impaired when facial stimuli are lit from below (i.e. chin-lit). Vertical contrast (i.e. horizontal lines) in facial images is particularly important for facial coding. Disruption of vertical contrast may underlie a range of manipulations detrimental to facial recognition, including lighting from below. Relative to their brow-lit counterparts, chin-lit faces have shadows and shading that are partially reversed along the horizontal axis, producing different bands of vertical contrast (e.g. shadows now fall above features that cast them). We investigated the contribution of horizontal and vertical image contrast to facial recognition across lighting conditions. Participants were trained to recognize chin- or brow-lit facial images of individuals. We recorded the extent to which training facilitated recognition of the target individuals in horizontally or vertically filtered images, taken under identical or alternate lighting conditions. We found that recognition was better facilitated by contrast along the vertical axis than the horizontal. Importantly, for images containing vertical contrast, recognition was impaired when matching chin-lit to brow-lit images (and vice versa). We interpret our results as further evidence that matching facial identities across images is particularity reliant on specific patterns of vertical contrast. We further conclude that these vertical templates make matching facial identity across lighting directions intrinsically vulnerable to extreme variation in lighting along the same axis.
Keywords:
shading,
Facial Coding,
Spatial Filtering,
image statistics,
Orientation Tuning
Conference:
ACNS-2012 Australasian Cognitive Neuroscience Conference, Brisbane, Australia, 29 Nov - 2 Dec, 2012.
Presentation Type:
Poster Presentation
Topic:
Sensation and Perception
Citation:
Pearce
SL
(2012). Contrast orientation and recognition of facial identity across variable lighting conditions.
Conference Abstract:
ACNS-2012 Australasian Cognitive Neuroscience Conference.
doi: 10.3389/conf.fnhum.2012.208.00185
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Received:
25 Oct 2012;
Published Online:
17 Nov 2012.
*
Correspondence:
Mr. Samuel L Pearce, University of Queensland, School of Psychology, Brisbane, Queensland, 4072, Australia, samuel.pearce@uqconnect.edu.au