Roncato Sergio, Guidi Stefano, Parlangeli Oronzo, Battaglini Luca
Department of Psychology, University of Padova Padova, Italy.
Department of Political, Social and Cognitive Sciences, University of Siena Siena, Italy.
Front Psychol. 2016 Jun 23;7:959. doi: 10.3389/fpsyg.2016.00959. eCollection 2016.
Perceptual grouping appears both as organized forms of real figural units and as illusory or "phantom" figures. The phenomenon is visible in the Hermann grid and in configurations which generate color spreading, e.g., "neon effects." These configurations, generally regular repetitive patterns, appear to be crossed by illusory bands filled with a brighter shade or a colored tinge connecting the various loci of illusory effects. In this work, we explore a particular new illusion showing a grouping effect. It manifests as illusory streaks irradiating from the vertexes of angular contours and connecting pairs of figures nearby. It is only clearly visible when more than one figure is shown, and takes the shape of a net crossing their corners. Although the grouping effect is vivid, the local source of the illusion is completely hidden. Theories explaining this effect as due to the irradiation of illusory streaks (mainly that of Grossberg and Mingolla, 1985a,b) do not fully explain the figural patterns presented here. Illusory effects have already been documented at the angles of various figures, causing them to alter in amplitude and brightness; however, the figure illustrated here appears to have different features and location. Phenomenological observations and an experiment were conducted to assess the role played by geometric and photometric parameters in this illusion. Results showed that sharp angles, in low contrast with the surround, are the main source of the illusion which, however, only becomes visible when at least two figures are close together. These findings are discussed with respect to theories of contour processing and perceptual grouping, and in relation to other illusions.
知觉分组既表现为真实图形单元的有组织形式，也表现为虚幻或“幻影”图形。这种现象在赫尔曼栅格以及产生颜色扩散的构型中可见，例如“霓虹效应”。这些构型通常是规则的重复图案，似乎被充满更亮色调或色彩的虚幻带穿过，这些带连接着虚幻效应的各个位点。在这项工作中，我们探索了一种呈现分组效应的特殊新错觉。它表现为从角轮廓的顶点辐射出并连接附近图形对的虚幻条纹。只有当展示多个图形时它才清晰可见，并且呈现为穿过它们角的网状形状。尽管分组效应很明显，但错觉的局部来源却完全隐藏着。将这种效应解释为由于虚幻条纹的辐射（主要是格罗斯伯格和明戈拉1985a、b提出的理论）并不能完全解释这里呈现的图形模式。在各种图形的角处已经记录到了虚幻效应，导致它们在幅度和亮度上发生变化；然而，这里展示的图形似乎具有不同的特征和位置。进行了现象学观察和一项实验来评估几何和光度学参数在这种错觉中所起的作用。结果表明与周围环境对比度低的锐角是错觉的主要来源，然而，只有当至少两个图形靠得很近时错觉才会显现出来。针对轮廓处理和知觉分组的理论以及与其他错觉相关的方面对这些发现进行了讨论。
