Data from: A novel system for bi-ocular eye-tracking in vertebrates with laterally placed eyes

1. Animals use vision to gather information about their environment and then use that information to make behavioural decisions that affect fitness. They will often move their heads or eyes to inspect areas of interest with their centres of acute vision, such as foveae, to gather high resolution information about potential mates, predation risks, or other aspects of the environment. Few studies to date have been able to accurately determine where laterally eyed animals direct their visual attention and how they use their eyes to gather information. 2. We present a non-invasive eye-tracking system that can simultaneously track the gaze of two eyes. This is particularly useful for studying animals with laterally placed eyes (most vertebrates) where the two eyes are viewing different images. This system can also accommodate comparative studies using animals of varying size, including small animals that are not frequently used in eye-tracking studies due to constraints of existing eye-tracking systems. We conducted an eye-tracking experiment with European starlings (Sturnus vulgaris) to test the eye-tracking system, calibration methods and highlight relevant aspects of experimental design. 3. We were able to accurately track the gaze of European starlings with <5 degrees of error. We also found that starlings are more likely to fixate on biologically relevant visual stimuli (e.g. predators and active prey) than simple stimuli (e.g. a dot) in video playbacks. 4. The method presented here can be used to address ecological and evolutionary questions about where animals direct their attention and how they visually inspect mates, food and predators, as well as address management questions about how animals inspect man-made objects. This method can also be used to answer fundamental questions about vision, such as how laterally eyed vertebrates coordinate the use of their eyes laterally and binocularly.1. 动物借助视觉获取生存环境的相关信息，并以此做出影响自身演化适合度（fitness）的行为决策。它们常会转动头部或眼球，利用自身的敏锐视觉中心（如中央凹（foveae））对目标区域进行检视，以获取潜在配偶、捕食风险或其他环境要素的高分辨率信息。截至目前，鲜有研究能够精准确定侧眼动物的视觉注意力投向何处，以及它们如何通过眼球运动获取视觉信息。 2. 我们提出一种可同时追踪双眼注视轨迹的无创眼动追踪系统（non-invasive eye-tracking system）。该系统尤其适用于侧置双眼（多数脊椎动物均为此类视觉结构）的动物研究——这类动物的双眼可获取不同的视觉图像。此外，该系统可适配不同体型的动物开展比较研究，包括因现有眼动追踪系统的限制而较少被用于眼动研究的小型动物。为验证该眼动追踪系统与校准方法，并明确实验设计的关键环节，我们以欧椋鸟（Sturnus vulgaris）为对象开展了眼动追踪实验。 3. 本研究实现了对欧椋鸟注视轨迹的精准追踪，追踪误差小于5°。同时我们发现，在视频回放实验中，相较于点状等简单视觉刺激，欧椋鸟更倾向于注视具有生物学意义的视觉刺激（如捕食者与活动猎物）。 4. 本研究所提出的方法可用于解答多个维度的科学问题：其一，可探索动物的视觉注意力投向与配偶、食物、捕食者的视觉检视模式等生态学与进化学议题；其二，可探究动物如何检视人工物体等应用管理类问题；此外，还可解答视觉研究的基础科学问题，例如侧眼脊椎动物如何协调单眼与双眼的视觉使用模式。