Abstract
The Ebbinghaus illusion is a classic example of the influence of a contextual surround on the perceived size of an object. Here, we introduce a novel variant of this illusion called the Dynamic Ebbinghaus illusion in which the size and eccentricity of the surrounding inducers modulates dynamically over time. Under these conditions, the size of the central circle is perceived to change in opposition with the size of the inducers. Interestingly, this illusory effect is relatively weak when participants are fixating a stationary central target, less than half the magnitude of the classic static illusion. However, when the entire stimulus translates in space requiring a smooth pursuit eye movement to track the target, the illusory effect is greatly enhanced, almost twice the magnitude of the classic static illusion. A variety of manipulations including target motion, peripheral viewing, and smooth pursuit eye movements all lead to dramatic illusory effects, with the largest effect nearly four times the strength of the classic static illusion. We interpret these results in light of the fact that motion-related manipulations lead to uncertainty in the image size representation of the target, specifically due to added noise at the level of the retinal input. We propose that the neural circuits integrating visual cues for size perception, such as retinal image size, perceived distance, and various contextual factors, weight each cue according to the level of noise or uncertainty in their neural representation. Thus, more weight is given to the influence of contextual information in deriving perceived size in the presence of stimulus and eye motion. Biologically plausible models of size perception should be able to account for the reweighting of different visual cues under varying levels of certainty.
Highlights
To accurately guide interactions with objects in the world, the visual system must construct the perceived size of an object from its retinal image size
In order to more fully evaluate the information uncertainty hypothesis, we present the Dynamic Ebbinghaus illusion, which incorporates the dynamic components of the Dynamic Illusory Size-Contrast (DISC) stimulus with the familiar concentric circles configuration of the Ebbinghaus stimulus
OF EXPERIMENT 1 In Experiment 1 we directly compared the magnitudes of two versions of the Dynamic Ebbinghaus illusion (Figure 3 and Movies 1, 2) with the classic static Ebbinghaus illusion (Figure 1) using a set of matched stimulus parameters (Figure 3A, bottom)
Summary
To accurately guide interactions with objects in the world, the visual system must construct the perceived size of an object from its retinal image size. A variety of contextual cues can bias this constructive process, such as physical and perceived distance (Emmert, 1881; Ponzo, 1911; Boring, 1940; Berryhill et al, 2009), an object’s geometrical and textural properties (Lotze, 1852; Kundt, 1863; Helmholtz, 1867; Murray et al, 2006; Westheimer, 2008; Giora and Gori, 2010), knowledge of an object’s typical size (Konkle and Oliva, 2012), and the relative size of different objects in a scene (Robinson, 1972; Coren and Girgus, 1978; Roberts et al, 2005) or the frame around an object (Kunnapas, 1955; Rock and Ebenholtz, 1959; Robinson, 1972; Brigell et al, 1977) These biases are revealed by many classic visual illusions in which the size of an object is misperceived. The classic Ebbinghaus illusion may cause a target circle to appear around 10–20% larger (or smaller) than it is (Massaro and Anderson, 1971; Jaeger and Pollack, 1977; Weintraub, 1979; Girgus and Coren, 1982; Roberts et al, 2005)
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