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

动物色彩模式的复杂性表明，在视觉世界的丰富感知体验中，我们并不孤单。例如，感知技巧和光学效果（视觉错觉）在动物身体图案中很常见，以传达伪装。由于这些已经进化到可以击败非人类观众的视觉检测或识别，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。深度的感知对于与视觉复杂的环境进行交互非常重要，这绝不是人类独有的任务。即使在没有双目线索的情况下，我们也能感知深度，这一点可以通过一张照片来简单地说明：我们通常可以通过透视、明暗和阴影等线索来从三维场景的二维再现中解释深度。尽管许多动物（例如爬行动物、昆虫和鸟类）感知视觉深度的能力已经被清楚地记录下来，但更难确定非人类动物可能使用哪些感知过程。目前，在非灵长类动物系统中还没有关于图像深度感知的系统研究。本项目将研究乌贼的伪装行为。乌贼为研究非人类的视觉感知提供了一个独特的系统，因为每种动物都能产生数千种不同的身体模式来进行伪装。动物表达的特定模式揭示了大量关于其视觉感知的信息：它如何看到周围的图案，形状和物体反映在身体模式中。这些身体模式是由对当地环境的直接视觉评估决定的，形成它们的色素细胞是在神经控制下的。因此，我们可以通过大脑在视觉输入和身体模式输出之间建立直接联系，从而对其视觉机制进行新的见解。这个系统更加迷人，因为乌贼是软体动物，它们的眼睛和大脑是从脊椎动物独立进化而来的，因为脊椎动物和软体动物的共同祖先最多只有初步的视觉。我们知道，头足类动物的相机型眼睛与脊椎动物的眼睛高度会聚，迄今为止的研究表明，这两类动物处理视觉信息的方式具有相似的原理。这个项目的目的是了解深度线索，无论是实际的还是图像的，如何影响乌贼的伪装反应，以及这反过来又如何影响其被潜在捕食者的可探测性。在这个项目中，我将探讨深度和视角在乌贼视觉系统中的重要性，以及它在制造和破坏伪装中扮演的角色。我将通过实验室和现场行为实验和图像分析来实现这一目标。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片。然而，这种孤立的线索在人工刺激的动物的生物相关性是有限的，其视觉生态不应被忽视。因此，这项建议补充了一个实验室为基础的“心理物理学”的方法与实地考察。乌贼的身体模式被认为是在很大程度上进化的捕食压力，从硬骨鱼类，这个建议的另一个组成部分将确定乌贼的身体模式的变化如何影响检测和识别硬骨鱼类，一个问题很大程度上被忽视的研究乌贼视觉和伪装的日期。这项工作将为非人类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.