Liinasuo M, Rovamo J, Kojo I
Department of Physiology, University of Helsinki, Finland.
Invest Ophthalmol Vis Sci. 1997 Nov;38(12):2554-65.
Illusory figures, created by the visual system between visualizing real objects, are probably caused by processes designed to segregate objects from background. Support ratio--that is, the ratio between the physically specified and total triangle side length--has been suggested to be the main spatial determinant for suprathreshold perception of a Kanizsa-type illusion. To test this scale invariance hypothesis at threshold, illusory figure perception was studied by determining the effects of inducer size and distance at various exposure durations and fixation strategies on the frequency of seeing (FoS) an illusory Kanizsa triangle.
The effect of various support ratios was studied in the first experiment by varying the intercenter distance between constant-size inducers viewed at various distances. In the second experiment, the effects of various exposure durations and fixation strategies were investigated; and the third experiment repeated the second one, with backward masking to control the processing time. In the fourth experiment, the magnification of the stimulus configuration was varied, with a support ratio that had yielded 100% FoS in the first experiment, to study the range of scale invariance in illusory figure perception.
The support ratio was the main determinant for the perception of an illusory figure at various inducer sizes, exposure durations, and masking conditions when fixation was steady; FoS always increased from 0% to 100% with the support ratio of 0.30 to 0.37. However, free viewing, with and without masking, resulted in 100% illusory figure perception at all support ratios tested. Furthermore, when fixation was steady and support ratio and exposure duration were held constant, stimulus magnification reduced FoS from 100% to 0% at the smallest and largest stimulus sizes.
The support ratio seems to be the main spatial determinant for illusory figure perception. However, scale invariance in Kanizsa triangle perception broke down in the smallest and largest configurations, probably because of the limitations of visual acuity and spatial integration, respectively. Integration of information from several fixations enhances FoS at small support ratios, emphasizing the importance of the binding process between separate fixations for illusory figure perception.
视觉系统在对真实物体进行视觉化的过程中所产生的虚幻图形，可能是由旨在将物体与背景分离的过程所引起的。支持率（即物理指定的三角形边长与总三角形边长之比）被认为是卡尼兹萨型错觉超阈值感知的主要空间决定因素。为了在阈值水平上检验这种尺度不变性假设，通过确定不同暴露持续时间和注视策略下诱导物大小和距离对虚幻卡尼兹萨三角形视见频率（FoS）的影响，研究了虚幻图形感知。
在第一个实验中，通过改变在不同距离观看的恒定大小诱导物之间的中心距，研究了各种支持率的影响。在第二个实验中，研究了各种暴露持续时间和注视策略的影响；第三个实验重复了第二个实验，并采用后向掩蔽来控制处理时间。在第四个实验中，改变刺激配置的放大倍数，采用在第一个实验中产生100%视见频率的支持率，以研究虚幻图形感知中的尺度不变性范围。
当注视稳定时，支持率是不同诱导物大小、暴露持续时间和掩蔽条件下虚幻图形感知的主要决定因素；随着支持率从0.30增加到0.37，视见频率总是从0%增加到100%。然而，无论有无掩蔽，自由观看在所有测试的支持率下都导致100%的虚幻图形感知。此外，当注视稳定且支持率和暴露持续时间保持恒定时，在最小和最大刺激大小时，刺激放大倍数会使视见频率从100%降至0%。
支持率似乎是虚幻图形感知的主要空间决定因素。然而，卡尼兹萨三角形感知中的尺度不变性在最小和最大配置中失效，可能分别是由于视力和空间整合的限制。来自多个注视的信息整合在小支持率下提高了视见频率，强调了单独注视之间的绑定过程对虚幻图形感知的重要性。
