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Bird colour vision: behavioural thresholds reveal receptor noise.

Olsson, Peter LU ; Lind, Olle LU and Kelber, Almut LU (2015) In Journal of Experimental Biology 218(2). p.184-193
Abstract
Birds have impressive physiological adaptations for colour vision, including tetrachromacy and coloured oil droplets, yet it is not clear exactly how well birds can discriminate the reflecting object colours that they encounter in nature. With behavioural experiments, we determined colour discrimination thresholds of chickens in bright and dim light. We performed the experiments with two colour series, orange and green, covering two parts of chicken colour space. These experiments allowed us to compare behavioural results with model expectations and determine how different noise types limit colour discrimination. At intensities ranging from bright light to those corresponding to early dusk (250-10 cd m(-2)), we describe thresholds... (More)
Birds have impressive physiological adaptations for colour vision, including tetrachromacy and coloured oil droplets, yet it is not clear exactly how well birds can discriminate the reflecting object colours that they encounter in nature. With behavioural experiments, we determined colour discrimination thresholds of chickens in bright and dim light. We performed the experiments with two colour series, orange and green, covering two parts of chicken colour space. These experiments allowed us to compare behavioural results with model expectations and determine how different noise types limit colour discrimination. At intensities ranging from bright light to those corresponding to early dusk (250-10 cd m(-2)), we describe thresholds accurately by assuming a constant signal-to-noise ratio, in agreement with an invariant Weber fraction of Weber's law. Below this intensity, signal-to-noise ratio decreases and Weber's law is violated because photon-shot noise limits colour discrimination. In very dim light (below 0.05cd m(-2) for the orange series or 0.2 cd m(-2) for the green series) colour discrimination is possibly constrained by dark noise, and the lowest intensity at which chickens can discriminate colours is 0.025 and 0.08 cd m(-2) for the orange and green series, respectively. Our results suggest that chickens use spatial pooling of cone outputs to mitigate photon-shot noise. Surprisingly, we found no difference between colour discrimination of chickens and humans tested with the same test in bright light. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Animal behaviour, Bird vision, Gallus gallus, Psychophysics, Visual modelling
in
Journal of Experimental Biology
volume
218
issue
2
pages
184 - 193
publisher
The Company of Biologists Ltd
external identifiers
  • pmid:25609782
  • wos:000348286900012
  • scopus:84964264780
ISSN
1477-9145
DOI
10.1242/jeb.111187
language
English
LU publication?
yes
id
37271ae2-7fbe-4038-8420-fdbbcc3d3b1d (old id 5040023)
date added to LUP
2015-02-11 11:30:08
date last changed
2017-09-03 03:30:00
@article{37271ae2-7fbe-4038-8420-fdbbcc3d3b1d,
  abstract     = {Birds have impressive physiological adaptations for colour vision, including tetrachromacy and coloured oil droplets, yet it is not clear exactly how well birds can discriminate the reflecting object colours that they encounter in nature. With behavioural experiments, we determined colour discrimination thresholds of chickens in bright and dim light. We performed the experiments with two colour series, orange and green, covering two parts of chicken colour space. These experiments allowed us to compare behavioural results with model expectations and determine how different noise types limit colour discrimination. At intensities ranging from bright light to those corresponding to early dusk (250-10 cd m(-2)), we describe thresholds accurately by assuming a constant signal-to-noise ratio, in agreement with an invariant Weber fraction of Weber's law. Below this intensity, signal-to-noise ratio decreases and Weber's law is violated because photon-shot noise limits colour discrimination. In very dim light (below 0.05cd m(-2) for the orange series or 0.2 cd m(-2) for the green series) colour discrimination is possibly constrained by dark noise, and the lowest intensity at which chickens can discriminate colours is 0.025 and 0.08 cd m(-2) for the orange and green series, respectively. Our results suggest that chickens use spatial pooling of cone outputs to mitigate photon-shot noise. Surprisingly, we found no difference between colour discrimination of chickens and humans tested with the same test in bright light.},
  author       = {Olsson, Peter and Lind, Olle and Kelber, Almut},
  issn         = {1477-9145},
  keyword      = {Animal behaviour,Bird vision,Gallus gallus,Psychophysics,Visual modelling},
  language     = {eng},
  number       = {2},
  pages        = {184--193},
  publisher    = {The Company of Biologists Ltd},
  series       = {Journal of Experimental Biology},
  title        = {Bird colour vision: behavioural thresholds reveal receptor noise.},
  url          = {http://dx.doi.org/10.1242/jeb.111187},
  volume       = {218},
  year         = {2015},
}