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Hülemeier AG, Lappe M. Limb articulation of biological motion can induce illusory motion perception during self-motion. Iperception 2024; 15:20416695241246755. [PMID: 38903983 PMCID: PMC11188058 DOI: 10.1177/20416695241246755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Accepted: 03/27/2024] [Indexed: 06/22/2024] Open
Abstract
When one walks toward a crowd of pedestrians, dealing with their biological motion while controlling one's own self-motion is a difficult perceptual task. Limb articulation of a walker is naturally coupled to the walker's translation through the scene and allows the separation of optic flow generated by self-motion from the biological motion of other pedestrians. Recent research has shown that if limb articulation and translation mismatch, such as for walking in place, self-motion perception becomes biased. This bias may reflect an illusory motion attributed to the pedestrian crowd from the articulation of their limbs. To investigate this hypothesis, we presented observers with a simulation of forward self-motion toward a laterally moving crowd of point-light walkers and asked them to report the perceived lateral speed of the crowd. To investigate the dependence of the crowd speed percept on biological motion, we also included conditions in which the points of the walker were spatially scrambled to destroy body form and limb articulation. We observed illusory crowd speed percepts that were related to the articulation rate of the biological motion. Scrambled walkers also produced illusory motion but it was not related to articulation rate. We conclude that limb articulation induces percepts of crowd motion that can be used for interpreting self-motion toward crowds.
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Affiliation(s)
- Anna-Gesina Hülemeier
- Institute for Psychology, University of Münster, Münster, North-Rhine Westphalia, Germany
| | - Markus Lappe
- Institute for Psychology, University of Münster, Münster, North-Rhine Westphalia, Germany
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Hülemeier AG, Lappe M. Illusory percepts of curvilinear self-motion when moving through crowds. J Vis 2023; 23:6. [PMID: 38112491 PMCID: PMC10732088 DOI: 10.1167/jov.23.14.6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 11/13/2023] [Indexed: 12/21/2023] Open
Abstract
Self-motion generates optic flow, a pattern of expanding visual motion. Heading estimation from optic flow analysis is accurate in rigid environments, but it becomes challenging when other human walkers introduce independent motion to the scene. Previous studies showed that heading perception is surprisingly accurate when moving through a crowd of walkers but revealed strong heading biases when either articulation or translation of biological motion were presented in isolation. We hypothesized that these biases resulted from misperceiving the self-motion as curvilinear. Such errors might manifest as opposite biases depending on whether the observer perceived the crowd motion as indication of his/her self-translation or self-rotation. Our study investigated the link between heading biases and illusory path perception. Participants assessed heading and path perception while observing optic flow stimuli with varying walker movements. Self-motion perception was accurate during natural locomotion (articulation and translation), but significant heading biases occurred when walkers only articulated or translated. In this case, participants often reported a curved path of travel. Heading error and curvature pointed in opposite directions. On average, participants perceived the walker motion as evidence for viewpoint rotation leading to curvilinear path percepts.
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Affiliation(s)
| | - Markus Lappe
- Department of Psychology, University of Münster, Münster, Germany
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Alexander E, Cai LT, Fuchs S, Hladnik TC, Zhang Y, Subramanian V, Guilbeault NC, Vijayakumar C, Arunachalam M, Juntti SA, Thiele TR, Arrenberg AB, Cooper EA. Optic flow in the natural habitats of zebrafish supports spatial biases in visual self-motion estimation. Curr Biol 2022; 32:5008-5021.e8. [PMID: 36327979 PMCID: PMC9729457 DOI: 10.1016/j.cub.2022.10.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 08/15/2022] [Accepted: 10/05/2022] [Indexed: 12/12/2022]
Abstract
Animals benefit from knowing if and how they are moving. Across the animal kingdom, sensory information in the form of optic flow over the visual field is used to estimate self-motion. However, different species exhibit strong spatial biases in how they use optic flow. Here, we show computationally that noisy natural environments favor visual systems that extract spatially biased samples of optic flow when estimating self-motion. The performance associated with these biases, however, depends on interactions between the environment and the animal's brain and behavior. Using the larval zebrafish as a model, we recorded natural optic flow associated with swimming trajectories in the animal's habitat with an omnidirectional camera mounted on a mechanical arm. An analysis of these flow fields suggests that lateral regions of the lower visual field are most informative about swimming speed. This pattern is consistent with the recent findings that zebrafish optomotor responses are preferentially driven by optic flow in the lateral lower visual field, which we extend with behavioral results from a high-resolution spherical arena. Spatial biases in optic-flow sampling are likely pervasive because they are an effective strategy for determining self-motion in noisy natural environments.
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Affiliation(s)
- Emma Alexander
- Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, Berkeley, CA 94720, USA,Present address: Department of Computer Science, Northwestern University, Evanston, IL 60208, USA,Lead contact,Correspondence:
| | - Lanya T. Cai
- Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, Berkeley, CA 94720, USA,Present address: Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Sabrina Fuchs
- Werner Reichardt Centre for Integrative Neuroscience, Institute of Neurobiology, University of Tubingen, 72076 Tubingen, Germany
| | - Tim C. Hladnik
- Werner Reichardt Centre for Integrative Neuroscience, Institute of Neurobiology, University of Tubingen, 72076 Tubingen, Germany,Graduate Training Centre for Neuroscience, University of Tubingen, 72074 Tubingen, Germany
| | - Yue Zhang
- Werner Reichardt Centre for Integrative Neuroscience, Institute of Neurobiology, University of Tubingen, 72076 Tubingen, Germany,Graduate Training Centre for Neuroscience, University of Tubingen, 72074 Tubingen, Germany,Present address: Department of Cellular and Systems Neurobiology, Max Planck Institute for Biological Intelligence in Foundation, 82152 Martinsried, Germany
| | - Venkatesh Subramanian
- Department of Biological Sciences, University of Toronto Scarborough, Toronto M1C 1A4, Canada
| | - Nicholas C. Guilbeault
- Department of Biological Sciences, University of Toronto Scarborough, Toronto M1C 1A4, Canada,Department of Cell and Systems Biology, University of Toronto, Toronto M5S 3G5, Canada
| | - Chinnian Vijayakumar
- Department of Zoology, St. Andrew’s College, Gorakhpur, Uttar Pradesh 273001, India
| | - Muthukumarasamy Arunachalam
- Department of Zoology, School of Biological Sciences, Central University of Kerala, Kerala 671316, India,Present address: Centre for Inland Fishes and Conservation, St. Andrew’s College, Gorakhpur, Uttar Pradesh 273001, India
| | - Scott A. Juntti
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Tod R. Thiele
- Department of Biological Sciences, University of Toronto Scarborough, Toronto M1C 1A4, Canada,Department of Cell and Systems Biology, University of Toronto, Toronto M5S 3G5, Canada
| | - Aristides B. Arrenberg
- Werner Reichardt Centre for Integrative Neuroscience, Institute of Neurobiology, University of Tubingen, 72076 Tubingen, Germany
| | - Emily A. Cooper
- Herbert Wertheim School of Optometry & Vision Science, University of California, Berkeley, Berkeley, CA 94720, USA,Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA
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Hülemeier AG, Lappe M. Combining biological motion perception with optic flow analysis for self-motion in crowds. J Vis 2020; 20:7. [PMID: 32902593 PMCID: PMC7488621 DOI: 10.1167/jov.20.9.7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
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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Affiliation(s)
| | - Markus Lappe
- Department of Psychology, University of Münster, Münster, Germany
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Abstract
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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Affiliation(s)
- Krischan Koerfer
- Institute for Psychology and Otto Creutzfeldt Center for Cognitive and Behavioral Neuroscience, University of Muenster, Muenster, Germany
| | - Markus Lappe
- Institute for Psychology and Otto Creutzfeldt Center for Cognitive and Behavioral Neuroscience, University of Muenster, Muenster, Germany
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