Document Detail

Why do seals have cones? Behavioural evidence for colour-blindness in harbour seals.
MedLine Citation:
PMID:  25452008     Owner:  NLM     Status:  Publisher    
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.
Christine Scholtyssek; Almut Kelber; Guido Dehnhardt
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2014-12-2
Journal Detail:
Title:  Animal cognition     Volume:  -     ISSN:  1435-9456     ISO Abbreviation:  Anim Cogn     Publication Date:  2014 Dec 
Date Detail:
Created Date:  2014-12-2     Completed Date:  -     Revised Date:  2014-12-3    
Medline Journal Info:
Nlm Unique ID:  9814573     Medline TA:  Anim Cogn     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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