Perception of scene-relative object movement: Optic flow parsing and the contribution of monocular depth cues

Abstract

We have recently suggested that the brain uses its sensitivity to optic flow in order to parse retinal motion into components arising due to self and object movement (e.g. Rushton, S. K., & Warren, P. A. (2005). Moving observers, 3D relative motion and the detection of object movement. Current Biology, 15, R542-R543). Here, we explore whether stereo disparity is necessary for flow parsing or whether other sources of depth information, which could theoretically constrain flow-field interpretation, are sufficient. Stationary observers viewed large field of view stimuli containing textured cubes, moving in a manner that was consistent with a complex observer movement through a stationary scene. Observers made speeded responses to report the perceived direction of movement of a probe object presented at different depths in the scene. Across conditions we varied the presence or absence of different binocular and monocular cues to depth order. In line with previous studies, results consistent with flow parsing (in terms of both perceived direction and response time) were found in the condition in which motion parallax and stereoscopic disparity were present. Observers were poorer at judging object movement when depth order was specified by parallax alone. However, as more monocular depth cues were added to the stimulus the results approached those found when the scene contained stereoscopic cues. We conclude that both monocular and binocular static depth information contribute to flow parsing. These findings are discussed in the context of potential architectures for a model of the flow parsing mechanism.

Multisensory Integration of Visual and Vestibular Signals Improves Heading Discrimination in the Presence of a Moving Object

“…Specifically, our findings are in agreement with those of Warren and Saunders (1995) who observed heading biases in the direction opposite to the object motion. However, Royden and Hildreth (1996) reported heading biases in the direction of object motion.…”

“…Consistent with our results for the visual condition, previous studies (Warren and Saunders, 1995;Royden andHildreth, 1996, 1999) also reported errors in visual heading perception in the presence of a moving object. Specifically, our findings are in agreement with those of Warren and Saunders (1995) who observed heading biases in the direction opposite to the object motion.…”

“…2C). Thus, consistent with previous findings for visual self-motion (Warren and Saunders, 1995), a moving object induced systematic biases in heading perception when self-motion was indicated by only visual or vestibular cues. Critically, however, the combination of visual and vestibular self-motion cues greatly reduced the bias induced by object motion (Fig.…”

“…Humans can judge their heading fairly accurately when moving through a stationary environment (Warren et al, 1988;Telford et al, 1995;Telford and Howard, 1996;Mapstone et al, 2006;Crane, 2012;Cuturi and MacNeilage, 2013). However, observers can exhibit more substantial errors when they judge heading in the presence of objects that move independently in the world (Warren and Saunders, 1995;Royden andHildreth, 1996, 1999;Mapstone and Duffy, 2010).…”

“…However, observers can exhibit more substantial errors when they judge heading in the presence of objects that move independently in the world (Warren and Saunders, 1995;Royden andHildreth, 1996, 1999;Mapstone and Duffy, 2010). Although previous psychophysical studies have demonstrated that the visual system is capable of parsing retinal image motion into components related to object motion and self-motion (Warren and Rushton, 2007;Matsumiya and Ando, 2009;Warren and Rushton, 2009a,b;Dokka et al, 2015), the heading errors induced by object motion suggest that the visual system, by itself, cannot fully dissociate object motion from self-motion.…”