Animal Behavior Graduate Group, University of California Davis, Davis, United States.
Department of Population Health and Reproduction, School of Veterinary Medicine, University of California Davis, Davis, United States.
Sci Rep. 2019 Jul 22;9(1):10592. doi: 10.1038/s41598-019-46799-0.
Animals' sensory systems evolved to efficiently process information from their environmental niches. Niches often include irregular shapes and rough textures (e.g., jagged terrain, canopy outlines) that must be navigated to find food, escape predators, and master other fitness-related challenges. For most primates, vision is the dominant sensory modality and thus, primates have evolved systems for processing complicated visual stimuli. One way to quantify information present in visual stimuli in natural scenes is evaluating their fractal dimension. We hypothesized that sensitivity to complicated geometric forms, indexed by fractal dimension, is an evolutionarily conserved capacity, and tested this capacity in rhesus macaques (Macaca mulatta). Monkeys viewed paired black and white images of simulated self-similar contours that systematically varied in fractal dimension while their attention to the stimuli was measured using noninvasive infrared eye tracking. They fixated more frequently on, dwelled for longer durations on, and had attentional biases towards images that contain boundary contours with higher fractal dimensions. This indicates that, like humans, they discriminate between visual stimuli on the basis of fractal dimension and may prefer viewing informationally rich visual stimuli. Our findings suggest that sensitivity to fractal dimension may be a wider ability of the vertebrate vision system.
动物的感觉系统进化到能够高效地处理来自其生态位的信息。生态位通常包括不规则的形状和粗糙的纹理（例如，锯齿状的地形、树冠轮廓），这些都必须加以导航才能找到食物、躲避捕食者，并掌握其他与适应能力相关的挑战。对于大多数灵长类动物来说，视觉是主导的感觉方式，因此灵长类动物已经进化出了处理复杂视觉刺激的系统。一种量化自然场景中视觉刺激中存在的信息量的方法是评估它们的分形维数。我们假设，对复杂几何形状的敏感性，由分形维数来衡量，是一种进化上保守的能力，并在恒河猴（Macaca mulatta）中测试了这种能力。猴子观看了成对的黑白模拟自相似轮廓图像，这些图像的分形维数系统地变化，而他们对刺激的注意力则通过非侵入性的红外眼动追踪来测量。他们更频繁地注视、更长时间地注视、并对具有更高分形维数的边界轮廓的图像产生注意力偏向。这表明，与人类一样，它们可以根据分形维数来区分视觉刺激，并且可能更喜欢观看信息丰富的视觉刺激。我们的研究结果表明，对分形维数的敏感性可能是脊椎动物视觉系统的更广泛的能力。
