Heading perception from optic flow in the presence of biological motion

Riddell, Hugh; Li, Li; Lappe, Markus

doi:10.1167/19.14.25

Cited by 9 publications

(14 citation statements)

References 64 publications

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“…Both explanations have in common, however, that heading biases are explained by the assumption that the visual system treats all image motion indiscriminately, as if resulting from self-motion in a rigid world, consistent with several previous studies ( Li, Ni, Lappe, Niehorster, & Sun, 2018 ; Riddell & Lappe, 2017 ; Riddell, Li, & Lappe, 2019 ). In the only-translation condition, this result is to be expected because the stimulus does not contain any information about the movement of the group itself.…”

Section: Discussionsupporting

confidence: 88%

“…This finding would be expected if the optic flow system, like in the case of independently moving objects ( Layton & Fajen, 2016a ; Li, Ni, Lappe, Niehorster, & Sun, 2018 ; Royden & Hildreth, 1996 ; Warren & Saunders, 1995 ), did not take biological motion into account, but rather treated the entire scene as if it would arise from a static world. Recent experiments using a walker embedded in an optic flow field, similar to the typical paradigm for independent object motion, reinforce this view ( Riddell, Li, & Lappe, 2019 ).…”

Section: Introductionmentioning

confidence: 92%

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Combining biological motion perception with optic flow analysis for self-motion in crowds

Hülemeier

Lappe

2020

Journal of Vision

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Heading estimation from optic flow relies on the assumption that the visual world is rigid. This assumption is violated when one moves through a crowd of people, a common and socially important situation. The motion of people in the crowd contains cues to their translation in the form of the articulation of their limbs, known as biological motion. We investigated how translation and articulation of biological motion influence heading estimation from optic flow for self-motion in a crowd. Participants had to estimate their heading during simulated self-motion toward a group of walkers who collectively walked in a single direction. We found that the natural combination of translation and articulation produces surprisingly small heading errors. In contrast, experimental conditions that either present only translation or only articulation produced strong idiosyncratic biases. The individual biases explained well the variance in the natural combination. A second experiment showed that the benefit of articulation and the bias produced by articulation were specific to biological motion. An analysis of the differences in biases between conditions and participants showed that different perceptual mechanisms contribute to heading perception in crowds. We suggest that coherent group motion affects the reference frame of heading perception from optic flow.

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Section: Discussionsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 92%

Combining biological motion perception with optic flow analysis for self-motion in crowds

Hülemeier

Lappe

2020

Journal of Vision

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“…The same is true for the studies by Riddell et al. (2017 , 2018 , 2019 ), which presented biological motion walkers for which the motion of the point lights was fully coupled to the motion of the walker. Li et al.…”

Section: Introductionsupporting

confidence: 56%

“…Unlike nonbiological rigid objects, the articulation pattern during walking contains information about the direction and speed of the walker's movement ( Giese & Lappe, 2002 ; Fujimoto & Sato, 2005 ; Masselink & Lappe, 2015 ; Thurman & Lu, 2016 ). Yet, recent experiments suggested that this information is not used for heading detection ( Riddell & Lappe, 2017 , 2018 ; Riddell et al., 2019 ). A walker traversing a scene produces heading bias much like nonbiological independently moving objects ( Riddell et al., 2019 ).…”

Section: Introductionmentioning

confidence: 99%

“…Yet, recent experiments suggested that this information is not used for heading detection ( Riddell & Lappe, 2017 , 2018 ; Riddell et al., 2019 ). A walker traversing a scene produces heading bias much like nonbiological independently moving objects ( Riddell et al., 2019 ). When the scene consists solely of an approaching point-light walker, heading estimates are consistent with the vector sum of the self-motion of the observer and the approaching motion of the walker ( Riddell & Lappe, 2017 ).…”

Section: Introductionmentioning

confidence: 99%

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Pitting optic flow, object motion, and biological motion against each other

Koerfer¹,

Lappe²

2020

Journal of Vision

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Heading estimation from optic flow is crucial for safe locomotion but becomes inaccurate if independent object motion is present. In ecological settings, such motion typically involves other animals or humans walking across the scene. An independently walking person presents a local disturbance of the flow field, which moves across the flow field as the walker traverses the scene. Is the bias in heading estimation produced by the local disturbance of the flow field or by the movement of the walker through the scene? We present a novel flow field stimulus in which the local flow disturbance and the movement of the walker can be pitted against each other. Each frame of this stimulus consists of a structureless random dot distribution. Across frames, the body shape of a walker is molded by presenting different flow field dynamics within and outside the body shape. In different experimental conditions, the flow within the body shape can be congruent with the walker's movement, incongruent with it, or congruent with the background flow. We show that heading inaccuracy results from the local flow disturbance rather than the movement through the scene. Moreover, we show that the local disturbances of the optic flow can be used to segment the walker and support biological motion perception to some degree. The dichotomous result that the walker can be segmented from the scene but that heading perception is nonetheless influenced by the flow produced by the walker confirms separate visual pathways for heading estimation, object segmentation, and biological motion perception.

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