Chromatic illumination discrimination ability reveals that human colour constancy is optimised for blue daylight illuminations

PLoS One. 2014 Feb 19;9(2):e87989. doi: 10.1371/journal.pone.0087989. eCollection 2014.

Abstract

The phenomenon of colour constancy in human visual perception keeps surface colours constant, despite changes in their reflected light due to changing illumination. Although colour constancy has evolved under a constrained subset of illuminations, it is unknown whether its underlying mechanisms, thought to involve multiple components from retina to cortex, are optimised for particular environmental variations. Here we demonstrate a new method for investigating colour constancy using illumination matching in real scenes which, unlike previous methods using surface matching and simulated scenes, allows testing of multiple, real illuminations. We use real scenes consisting of solid familiar or unfamiliar objects against uniform or variegated backgrounds and compare discrimination performance for typical illuminations from the daylight chromaticity locus (approximately blue-yellow) and atypical spectra from an orthogonal locus (approximately red-green, at correlated colour temperature 6700 K), all produced in real time by a 10-channel LED illuminator. We find that discrimination of illumination changes is poorer along the daylight locus than the atypical locus, and is poorest particularly for bluer illumination changes, demonstrating conversely that surface colour constancy is best for blue daylight illuminations. Illumination discrimination is also enhanced, and therefore colour constancy diminished, for uniform backgrounds, irrespective of the object type. These results are not explained by statistical properties of the scene signal changes at the retinal level. We conclude that high-level mechanisms of colour constancy are biased for the blue daylight illuminations and variegated backgrounds to which the human visual system has typically been exposed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Color Perception / physiology*
  • Color*
  • Discrimination, Psychological / physiology*
  • Female
  • Humans
  • Light*
  • Male
  • Young Adult

Grant support

This project was part of a larger project funded by the Engineering and Physical Sciences Research Council (EPSRC), grant number: EP/H022236/1. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.