Papildomų objektų įtaka stimulo ilgio ir kampo dydžio suvokimui

This study describes experiments in which subjects adjusted the spatial positions of spots in three different kinds of basic stimuli in order to best perceive a required spatial property: 1) vernier alignment in a three-spot line arrangement, 2) orthogonality in a right-angled triangle constructed of three spots, or 3) length equality in a Brentano type figure. The magnitudes of the perceptual errors were measured as functions of the distance between the spots and flanking objects placed in close proximity to the spot stimuli. Quantitative characteristics of the strengths of the different illusions were obtained with the flanking objects placed at varying extents of spatial separation. The data were interpreted in terms of centroid biases caused by local integration processes. An appropriate analytical description of the experimental data was proposed, and good correspondence between it and the data was obtained. The calculated spatial parameters of the local lateral integration showed a linear dependence on the stimulus size.Šiame straipsnyje aprašomi eksperimentai, kuriuose stebėtojų prašoma pastumti vieną iš trijų pagrindinių stimulo dėmelių į vietą, tenkinančią reikalavimą: 1) trys dėmelės išsirikiuoja viena linija arba 2) išsidėsto stačiu kampu, arba 3) abu Brentano tipo iliuzinės figūros intervalai tampa vienodo ilgio. Suvokimo klaidų dydis matuojamas kaip atstumo tarp dėmelių ir šalia jų esančių papildomų objektų funkcijos. Gautos šių objektų sukeliamų skirtingų geometrinių iliuzijų kiekybinės charakteristikos. Eksperimentų duomenys interpretuojami, remiantis lokalios jaudinimų integracijos ir svorio centro postūmio samprata. Pasiūlytos atitinkamos analitinės funkcijos gana tiksliai aproksimuoja eksperimentines kreives. Išskaičiuotieji erdviniai lokaliosios integracijos parametrai yra tiesiškai susiję su bendruoju stimulo dydžiu

Oppel‑Kundt illusion balance

Perceptual estimates of spatial dimensions of visual objects depend on their shape and surface attributes. The present psychophysical study emphasizes two main contributors to the Oppel‑Kundt illusion: the outline of the filled space and the mode of filling. In past experiments, both factors have been considered significant. Our experiments were performed by using combined stimuli of the Oppel‑Kundt figures and supplementary objects situated within the empty intervals of the figures. Line segments, empty and filled rectangles, blurred contours, and grey and color images were used for the supplementary stimuli role. The experimental data demonstrated an innate property of the objects to balance the illusion of distance if they were placed within the Oppel‑Kundt figure and to create an illusion of extent when compared with an empty space interval. Both the balance magnitude and the induced illusion strength varied depending on the objects' spatial structure. The supplementary objects showed a tendency to differ from each other by their functional capacity and were ranked from lowest to highest: a line segment, a solid bar with a blurred outline, a contour of a rectangle, a solid fill rectangle, greyscale patterns, and color pictures. The experimental findings provided support for an explanation of the Oppel‑Kundt illusion in terms of the spatial‑temporal summation of excitations representing the object outline and surface attributes at the lower cortical levels of the visual system. Along with the facts already established in current literature, the experimental data gave rise to the assumption that any visual object could appear larger than its occupied area, and that the Oppel‑Kundt illusion could become a separate case in the common sensory phenomenon of object size illusion

Three-part Oppel-Kundt illusory figure

The Oppel-Kundt illusion was examined in the psychophysical experiments with the classical two-part stimuli and modified three-part figures. The modified versions comprised either one filled medial interval and two empty flanking intervals or one empty space situated in between two fillings. The illusion was measured as a function of the number of filling elements in the referential parts of the figures. The curves obtained by two modified figures and by the original two-part stimulus were quite similar in shape, but the magnitudes of the illusions differed significantly. The figure with two filled intervals yielded about twice-stronger illusory effect than the contrasting figure with a single filled and two empty intervals. The two-part stimulus showed the illusion magnitudes in the midst. Our assumption suggests the illusory effect being related particularly to overestimations of the filled interval when compared with the empty interval displayed side-to-side. The unfilled interval might not contribute to the illusion

Psychophysical measurements of illusion of the puffy circle

The strength of an illusion of curvature created by an equilateral triangle, square or pentagon inscribed in a circle has been measured in the psychophysical experiments. The arcs of the circle looked as if they were bowed outwards in the stimuli of various sizes, but, at a fixed diameter of the circumscribed circle, the triangles produced the strongest, and the pentagons, the weakest illusion. The strength of the illusion augmented with the stimulus diameter. Concave and convex sides of the inscribed figures caused less illusory effect than the straight ones. Similar distortions of the stimuli have been observed in the output of a neurophysiological model of spatial frequency filtering of images, and the computed curves resembled those of the experimental data, in respect to their shape and quantitative values