Investigating depth perception in non-human vision using the dynamic camouflage of cuttlefish

动物色彩图案的复杂性表明，我们并不是唯一对视觉世界有丰富感知体验的人。例如，感知技巧和视觉效果(视觉错觉)在传达伪装的动物身体模式中很常见。由于它们已经进化到无法通过非人类观察者的视觉检测或识别，它们对我们自己的视觉系统的有效性表明了视觉处理的共同原则。深度感知对于与视觉复杂的环境互动非常重要，这项任务绝不是人类独有的。我们即使在没有双目线索的情况下也能感知深度，就像通过考虑一张照片来简单地说明的那样：对于我们来说，使用透视、阴影和阴影等线索来解释这一三维场景的二维再现的深度通常是微不足道的。虽然感知视觉深度的能力在许多群体(如爬行动物、昆虫和鸟类)中都有明确的记录，但更难确定非人类动物可能使用的感知过程。目前还没有关于非灵长类动物系统中图形深度知觉的系统研究。本项目将研究乌贼乌贼的伪装行为。乌贼为研究非人类的视觉感知提供了一个独特的系统，因为每种动物都可以产生数千种不同的身体模式来伪装。动物所表达的特定图案在很大程度上揭示了它的视觉感知：它如何看待周围的图案、形状和物体反映在身体图案中。这些身体模式是由对当地环境的直接视觉评估确定的，形成它们的色团是在神经控制下的。因此，我们被提供了视觉输入和通过大脑的身体模式输出之间的直接联系，从而可以对其视觉机制进行新的洞察。这个系统更令人着迷，因为墨鱼是软体动物，其眼睛和大脑是从脊椎动物独立进化出来的，因为脊椎动物和软体动物的共同祖先充其量只有基本的视力。我们知道，头足类动物的相机状眼睛与脊椎动物的眼睛高度融合，到目前为止的研究表明，这两个群体处理视觉信息的方式具有相似的原理。这项建议旨在了解深度线索，无论是实际的还是图片的，如何影响乌贼的伪装反应，以及这反过来如何影响其被潜在捕食者检测到。在这个项目中，我将探索深度和透视在墨鱼视觉系统中的重要性，以及它在伪装的形成和破坏中扮演的角色。我将通过实验室和现场的行为实验和图像分析来实现这一点。测试乌贼对孤立视觉信息的反应的能力意味着我们可以采取类似于人类心理物理学的方法，依次测试一系列精心控制的参数，以构建这种动物如何感知和使用深度的完整图景。然而，人工刺激中这种孤立的线索对动物的生物学相关性是有限的，其视觉生态不应被忽视。因此，这项建议是对以实验室为基础的“心理物理学”方法与实地考察的补充。乌贼的身体模式被认为在很大程度上是由于硬骨鱼的捕食压力而进化的；这一提议的另一个组成部分将确定乌贼身体模式的变化如何影响硬骨鱼的检测和识别，这是迄今为止在乌贼视觉和伪装研究中基本上被忽视的一个主题。这项工作将为非人类的视觉处理和伪装的制作和破坏提供新的见解。

The complexity of animal colouration patterns suggests we are not alone in our rich perceptual experience of the visual world. For instance, perceptual tricks and optical effects (visual illusions) are common in animal body patterns that convey camouflage. As these have evolved to defeat visual detection or recognition by non-human viewers, their effectiveness against our own visual system suggests common principles of visual processing. The perception of depth is important for interacting with a visually complex environment, a task that is by no means unique to humans. We perceive depth even in the absence of binocular cues, as is simply illustrated by considering a photograph: it is usually trivial for us to interpret depth from this two-dimensional rendition of a three-dimensional scene using cues such as perspective, shading and shadows. Although the ability to perceive visual depth has been clearly documented in many groups (e.g. reptiles, insects and birds) it is more difficult to determine what perceptual processes might be used by non-human animals. There is currently no systematic research on pictorial depth perception in a non-primate system.This project will study the camouflage behaviour of the cuttlefish Sepia. Sepia offers a unique system for investigating non-human visual perception because each animal can produce thousands of different body patterns for camouflage. The particular pattern that an animals expresses reveals a great deal about its visual perception: how it sees patterns, shapes and objects around it is reflected in the body pattern. These body patterns are determined by direct visual assessment of the local environment and the chromatophores that form them are under neural control. Therefore we are afforded a direct link between visual input and body pattern output via the brain, allowing novel insight into its visual mechanisms. This system is all the more fascinating because cuttlefish are molluscs whose eye and brain have evolved independently from vertebrates, as the common ancestor of vertebrates and molluscs had rudimentary vision at best. We know that the camera-type eyes of cephalopods are highly convergent with the vertebrate eye, and research to date suggests that similar principles underlie the ways in which these two groups process visual information. This proposal aims to understand how depth cues, be they actual or pictorial, influence the camouflage response of Sepia, and how in turn this affects its detectability by potential predators.In this project I will explore the importance of depth and perspective in the cuttlefish visual system, and what part it plays in making and breaking camouflage. I will achieve this through laboratory and field behavioural experiments and image analysis. The ability to test the response of Sepia to isolated visual information means we can take an approach similar to that used in human psychophysics, testing a series of carefully controlled parameters in turn to build a complete picture of how depth is perceived and used by this animal. However, the biological relevance of such isolated cues in artificial stimuli to the animal is limited, and its visual ecology should not be neglected. Therefore this proposal complements a laboratory based "psychophysics" approach with fieldwork. The body patterns of Sepia are believed to have evolved largely in response to predation pressure from teleost fishes; a further component of this proposal will determine how changes in Sepia's body patterning affect detection and recognition by teleost fishes, a subject largely neglected in studies of Sepia vision and camouflage to date. This work will provide new insights into both non-human visual processing and camouflage making and breaking.