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SUMMARY:Material matters: the brain knows the binocular statistics of glos
 s - Dr Andrew Welchman\, Department of Psychology
DTSTART:20150129T130000Z
DTEND:20150129T140000Z
UID:TALK56747@talks.cam.ac.uk
CONTACT:John Mollon
DESCRIPTION:Whether choosing fresh fish\, or walking on wet tiles\, the vi
 sual impression of surface properties influences diverse behaviours. Specu
 larity—the extent to which a surface reflects light like a mirror—conv
 eys important information about an object’s physical properties such as 
 its composition\, smoothness and physical state (e.g. wet or dry). To esti
 mate a surface’s reflectance or gloss\, the brain must make an inference
  based on retinal images that result from unknown physical properties of t
 he environment related to (i) three-dimensional shape\; (ii) surface refle
 ctance and (iii) the illumination field. While disentangling these unknown
 s is formally intractable\, a biological and/or computational solution is 
 likely to be found in the characteristic image properties obtained when vi
 ewing reflective objects. This idea has a long history (e.g.\, Helmholtz)\
 , however we have limited formal understanding of which signals the human 
 visual system uses to estimate gloss. Here I use computational image analy
 sis and human psychophysics to suggest a role for disparity statistics in 
 driving gloss perception. Identifying these cues suggests a straightforwar
 d means for the brain to estimate surface attributes using low-level image
  signals rather than depending on complex physical models.
LOCATION:Kenneth Craik Room\, Craik-Marshall Building\, Downing Site
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