Scholtyssek Christine, Kelber Almut, Dehnhardt Guido
Lund Vision Group, Functional Zoology, Department of Biology, Lund University, Sölvegatan 35, 22362, Lund, Sweden,
Anim Cogn. 2015 Mar;18(2):551-60. doi: 10.1007/s10071-014-0823-3. Epub 2014 Dec 2.
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.
所有海豹和鲸类动物都至少失去了两种原始视锥细胞类型中的一种，因此应该是色盲。然而，早期研究表明，这些海洋哺乳动物能够辨别颜色，并且有人提出了一种色觉机制，该机制将视锥细胞和视杆细胞的信号进行对比。然而，这些早期研究低估了这些动物的亮度辨别能力，以至于它们可能仅通过亮度来辨别颜色。通过一项心理物理学辨别实验，我们表明港海豹仅通过亮度辨别就能解决颜色辨别任务。在进行的一系列实验中，两只港海豹必须辨别颜色的亮度，我们还发现了有力证据，表明在导致其他哺乳动物出现中间视觉（基于视杆细胞和视锥细胞）的光照水平下，港海豹具有纯粹的暗视觉（基于视杆细胞）。这一发现反驳了港海豹具有基于视杆细胞和视锥细胞的色觉这一观点。为了测试色盲情况，我们采用了一种认知方法，让一只经过训练能使用相同和不同概念的港海豹参与实验。我们用颜色相同或不同的等亮度刺激对来测试这只海豹。如果这只海豹能感知颜色，它就会对刺激之间的颜色差异做出反应。然而，这只海豹的反应是“相同”，这为色盲提供了有力证据。
