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Why do seals have cones? Behavioural evidence for colour-blindness in harbour seals.

Scholtyssek, Christine LU ; Kelber, Almut LU and Dehnhardt, Guido (2015) In Animal Cognition 18(2). p.551-560
Abstract
All seals and cetaceans have lost at least one of two ancestral cone classes and should therefore be colour-blind. Nevertheless, earlier studies showed that these marine mammals can discriminate colours and a colour vision mechanism has been proposed which contrasts signals from cones and rods. However, these earlier studies underestimated the brightness discrimination abilities of these animals, so that they could have discriminated colours using brightness only. Using a psychophysical discrimination experiment, we showed that a harbour seal can solve a colour discrimination task by means of brightness discrimination alone. Performing a series of experiments in which two harbour seals had to discriminate the brightness of colours, we also... (More)
All seals and cetaceans have lost at least one of two ancestral cone classes and should therefore be colour-blind. Nevertheless, earlier studies showed that these marine mammals can discriminate colours and a colour vision mechanism has been proposed which contrasts signals from cones and rods. However, these earlier studies underestimated the brightness discrimination abilities of these animals, so that they could have discriminated colours using brightness only. Using a psychophysical discrimination experiment, we showed that a harbour seal can solve a colour discrimination task by means of brightness discrimination alone. Performing a series of experiments in which two harbour seals had to discriminate the brightness of colours, we also found strong evidence for purely scotopic (rod-based) vision at light levels that lead to mesopic (rod-cone-based) vision in other mammals. This finding speaks against rod-cone-based colour vision in harbour seals. To test for colour-blindness, we used a cognitive approach involving a harbour seal trained to use a concept of same and different. We tested this seal with pairs of isoluminant stimuli that were either same or different in colour. If the seal had perceived colour, it would have responded to colour differences between stimuli. However, the seal responded with "same", providing strong evidence for colour-blindness. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Animal Cognition
volume
18
issue
2
pages
551 - 560
publisher
Springer
external identifiers
  • pmid:25452008
  • wos:000349626900014
  • scopus:84925541348
ISSN
1435-9456
DOI
10.1007/s10071-014-0823-3
language
English
LU publication?
yes
id
d7125f3c-d4d3-4a1e-8de9-8d5fa34f42da (old id 4913232)
date added to LUP
2015-01-15 13:04:02
date last changed
2017-04-30 06:01:51
@article{d7125f3c-d4d3-4a1e-8de9-8d5fa34f42da,
  abstract     = {All seals and cetaceans have lost at least one of two ancestral cone classes and should therefore be colour-blind. Nevertheless, earlier studies showed that these marine mammals can discriminate colours and a colour vision mechanism has been proposed which contrasts signals from cones and rods. However, these earlier studies underestimated the brightness discrimination abilities of these animals, so that they could have discriminated colours using brightness only. Using a psychophysical discrimination experiment, we showed that a harbour seal can solve a colour discrimination task by means of brightness discrimination alone. Performing a series of experiments in which two harbour seals had to discriminate the brightness of colours, we also found strong evidence for purely scotopic (rod-based) vision at light levels that lead to mesopic (rod-cone-based) vision in other mammals. This finding speaks against rod-cone-based colour vision in harbour seals. To test for colour-blindness, we used a cognitive approach involving a harbour seal trained to use a concept of same and different. We tested this seal with pairs of isoluminant stimuli that were either same or different in colour. If the seal had perceived colour, it would have responded to colour differences between stimuli. However, the seal responded with "same", providing strong evidence for colour-blindness.},
  author       = {Scholtyssek, Christine and Kelber, Almut and Dehnhardt, Guido},
  issn         = {1435-9456},
  language     = {eng},
  number       = {2},
  pages        = {551--560},
  publisher    = {Springer},
  series       = {Animal Cognition},
  title        = {Why do seals have cones? Behavioural evidence for colour-blindness in harbour seals.},
  url          = {http://dx.doi.org/10.1007/s10071-014-0823-3},
  volume       = {18},
  year         = {2015},
}