No special treatment of independent object motion for heading perception

Abstract

How do we judge the direction of self-motion (i.e., heading) in the presence of independent object motion? Previous studies that examined this question confounded the effects of a moving object's speed and its position on heading judgments, and did not examine whether the visual system uses salient nonmotion visual cues (such as color contrast and binocular disparity) to segment a moving object from global optic flow prior to heading estimation. The current study addressed these issues with both behavioral testing and computational modeling. Our results show that the visual system does not treat independent object motion separately for the perception of heading during self-motion. This is surprising because we all can segment a moving object from global optic flow and perceive its scene-relative motion independent of self-motion. Our findings support the claim that the perception of self-motion with independent object motion and the perception of object motion during self-motion are performed by different neural mechanisms.

Heading perception from optic flow in the presence of biological motion

“…Previous studies found that independently moving objects affected heading judgments only when they obscured or were in close proximity to the FOE of the background optic flow (Layton & Fajen, 2015, 2016a, 2016bRoyden & Hildreth, 1996;Warren & Saunders, 1995). In contrast, Li et al (2018) showed that independently moving objects can affect heading judgments even when they are not close to the FOE of the background optic flow. In Experiment 2, we sought to test whether normal PLWs and scrambled PLWs could bias heading estimation in a similar way when they are away from the FOE of the background optic flow.…”

“…A blank area in the size of the walker and void of background dots was placed behind the walker, such that none of the background points interspersed the walker at any time during the trial. This was done in order to make the current experiment more comparable to similar experiments, by Li et al (2018). As in Experiment 1, a control condition with no moving object was also tested.…”

“…More recent studies found that moving objects can produce a heading bias when they are in close proximity, but do not obscure the FOE (Layton & Fajen, 2015). Li et al (2018) showed that a laterally moving object can also induce a bias in heading judgments if the speed of the moving object is comparable to the speed of the background flow. They proposed a simple explanation based on the simulations of a long-standing model of heading perception (Lappe & Rauschecker, 1993).…”

“…Given the apparent robustness of heading detection mechanisms, it is somewhat surprising that one of the most common sources of noise in the visual environment, the motion generated by an object moving independently to the observer, has been shown to bias heading estimates by up to several degrees of visual angle (Layton & Fajen, 2015, 2016bLi, Ni, Lappe, Niehorster, & Sun, 2018; Citation: Riddell, H., Li, L., & Lappe, M. (2019). Heading perception from optic flow in the presence of biological motion.…”

“…According to model simulations, the latter case is accounted for by a rotational component of observer/eye motion in addition to the translational component. Consequently, Li et al (2018) concluded that heading biases reflect a pooling of the entire flow, a full analysis of self-motion components, and a lack of accounting for the moving object.…”