The Perception of Colour and Contrast in Complex Configurations

One of my major research projects focuses on the effects of the spatial structure of visual scenes on the appearance of parts of such scenes. The appearance of a surface as white, grey, or green is determined not only by the light reflected from that surface but also by the light reflected from surrounding regions. The change in the appearance of a surface caused by its juxtaposition with other surfaces is referred to as an induction. Although much studied, many colour induction phenomena still await a satisfactory explanation. My initial results implied that early sensory processing must be accompanied by a more elaborate stage of perceptual interpretation and surface analysis in order to achieve reliable perception of surface colours. I have been investigating the perception of colour and contrast in complex scenes with special emphasis on the possible mechanisms by which cues that are used to perceive three-dimensional organisation influence perceived contrast and colour. Such cues have to be factored into any adequate explanation of colour and contrast induction. Understanding the mechanisms by which these perceptual cues modify and affect the output of low-level mechanisms as well as their involvement in processes such as surface segmentation and figure ground segregation will eventually lead to mechanistic models that can explain surface perception in natural settings.

Publications

Spehar B Clifford CWG 2002 "Painting with light by Nick Carter: dramatic failures of colour constancy in articulated scenes" Perception 31 197-200 PDF

Speher B Clifford CWG Agostini T 2002 "Induction in vartiants of White's effect: common or separate mechanisms?" Perception 31 189-96 PDF

Spehar B Zaidi Q 1997 "New configurational effects on perceived contrast and brightness: second order White's effects" Perception 26 409-17

Zaidi Q Spehar B 1997 "Induced effects of backgrounds and foregrounds in pictures of three-dimensional configurations: the role of T junctions" Perception 26 395-408

Spehar B Gilchrist AL Arend LE 1995 "The critical role of relative luminance relations in White's effect and grating induction" Vision Research 35 2603-14 PDF

Spehar B Arend LA Gilchrist AL 1995 "Contrast-contrast: interactions between spatial and luminance factors" Review of Psychology 2 3-12

Arend LE Spehar B 1993 "Lightness, Brightness and Brightness Contrast: Illuminance Variation" Perception and Psychophysics 54 446-56

Arend LE Spehar B 1993 "Lightness, Brightness and Brightness Contrast: Reflectance Variation" Perception and Psychophysics 54 457-68

Funding sources:

ARC Small Grant Scheme in 1997 and 1998.

ARC Discovery Grant, 2003-2005.