Department of General Psychology, University of Padova, Padova, Italy.
Padua Neuroscience Center, University of Padova, Padova, Italy.
PLoS One. 2020 May 14;15(5):e0233157. doi: 10.1371/journal.pone.0233157. eCollection 2020.
The horizontal-vertical (HV) illusion is characterized by a tendency to overestimate the length of vertically-arranged objects. Comparative research is primarily confined to primates, a range of species that, although arboreal, often explore their environment moving along the horizontal axis. Such behaviour may have led to the development of asymmetrical perceptual mechanisms to make relative size judgments of objects placed vertically and horizontally. We observed the susceptibility to the HV illusion in fish, whose ability to swim along the horizontal and vertical plane permits them to scan objects' size equally on both axes. Guppies (Poecilia reticulata) were trained to select the longer orange line to receive a food reward. In the test phase, two arrays, containing two same-sized lines were presented, one horizontally and the other vertically. Black lines were also included in each pattern to generate the perception of an inverted T-shape (where a horizontal line is bisected by a vertical one) or an L-shape (no bisection). No bias was observed in the L-shape, which supports the idea of differential perceptual mechanisms for primates and fish. In the inverted T-shape, guppies estimated the bisected line as shorter, providing the first evidence of a length bisection bias in a fish species.
水平-垂直（HV）错觉的特征是倾向于高估垂直排列物体的长度。比较研究主要局限于灵长类动物，这些物种虽然生活在树上，但经常沿着水平轴移动来探索环境。这种行为可能导致了不对称的感知机制的发展，以便对垂直和水平放置的物体进行相对大小的判断。我们观察到鱼类容易受到 HV 错觉的影响，因为它们能够在水平和垂直平面上游泳，从而能够在两个轴上平等地扫描物体的大小。将孔雀鱼（Poecilia reticulata）训练为选择较长的橙色线以获得食物奖励。在测试阶段，呈现两个包含两条相同大小的线的数组，一条水平放置，另一条垂直放置。每个图案中还包括黑线，以产生倒置 T 形（其中一条水平线被另一条垂直线等分）或 L 形（不分叉）的感知。在 L 形中没有观察到偏差，这支持了灵长类动物和鱼类具有不同的感知机制的观点。在倒置 T 形中，孔雀鱼将被等分的线估计为较短，这首次提供了鱼类对线等分偏差的证据。
