A Binocular Information Source for Size Perception

Abstract

For too long, size perception research has been guided by the size distance invariance hypothesis. Although research to validate this hypothesis has been largely inconclusive, the hypothesis has endured, perhaps in part because alternative information sources for size perception were lacking. Here, I propose a binocular information source for size perception. The model, drawing on the binocular geometry of viewing a physical extent, is expressed solely in terms of four angular measures and interocular distance, with the explicit exclusion of egocentric distance information. Thus, the proposed information source, if utilized by the binocular system, should be able to augment the few existing sources of information for size perception (e.g., familiar size, texture gradient, and horizon ratio).

Independence of Size and Distance in Binocular Vision

“…If, as the SDIH predicts, S ′ is derived from visual angle 𝜃 by taking D ′ into account, the partial correlation between 𝜃 and S ′ should be zero when the effect of D ′ is controlled. If, on the other hand, as contended here, S ′ and D ′ are independent, or more specifically, S ′ is directly perceived by the information conveyed by Kim’s (2017) binocular variable, a high bivariate correlation between S ′ and object size S should remain unaffected even when the influences of D ′ or any other candidate intervening variables, such as 𝜃 or convergence angle ϕ , are held constant. For correlation analyses, 𝜃 , ϕ, S , and D were entered as stimulus (or manipulated) variables 4 and S ′ and D ′ as perceptual (or responding) variables.…”

“…Recently, Kim (2017) proposed an alternative source of information that the binocular visual system could utilize to detect an object’s size—the horizontal extent of an object. Drawing on the binocular geometry of viewing a fronto-parallel line segment AB ( Figure 1B ), the proposed variable is expressed as follows:…”

“…This is problematic. The present study set out to determine whether the binocular visual system utilizes the SDIH or an alternative source information, such as that proposed by Kim (2017) , to perceive an object’s size. To this end, three experiments were conducted in which participants viewed a virtual object stereoscopically then judged its size and distance.…”

“…To this end, three experiments were conducted in which participants viewed a virtual object stereoscopically then judged its size and distance. The first two experiments ascertained whether perceived (stereoscopic) size and perceived (stereoscopic) distance are interdependent, as predicted by the SDIH, or independent, as entailed by Kim’s (2017) proposed binocular information source. The results showed little evidence that the two perceptual qualities are related, thus contradicting the SDIH.…”

“…A possible alternative to SDIH now exists. The binocular source of size information proposed by Kim (2017) provides metric information about an object’s size. Comprised of four angular measures and the interpupillary distance (IPD), with the explicit exclusion of egocentric distance information, Kim’s binocular variable demands independence of perceived size and perceived distance, whereas the SDIH assumes interdependence of the two percepts.…”