Perspective Reversible Figures in Microgravity (Reversible Figures) - 09.17.14

Overview | Description | Applications | Operations | Results | Publications | Imagery
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The Perspective Reversible Figures in Microgravity (Reversible Figures) experiment is improving our knowledge of how astronaut perception is altered in space, where gravity cannot help with orientation. This could help in finding/developing countermeasures alleviating any disorientation experienced by astronauts especially during key activities such as spacewalks and docking/undocking of spacecraft.

Science Results for Everyone
Information Pending

The following content was provided by Gilles Clement, Ph.D., and is maintained in a database by the ISS Program Science Office.
Information provided courtesy of the Erasmus Experiment Archive.

Experiment Details


Principal Investigator(s)

  • Gilles Clement, Ph.D., International Space University (ISU), Strasbourg, France

  • Co-Investigator(s)/Collaborator(s)
  • Alexandra Kindrat, MSc, International Space University (ISU), Strasbourg, France
  • Alexander Melinyshyn, BSc, International Space University (ISU), Strasbourg, France
  • Tahir Merali, MS, International Space University (ISU), Strasbourg, France
  • Michael Demel, International Space University (ISU), Strasbourg, France
  • Robert B. Thirsk, Ph.D., Canadian Space Agency (CSA), St. Hubert, Quebec, Canada

  • Developer(s)
    CADMOS, Toulouse, , France

    Space Applications Services, Zaventum, , Belgium

    Sponsoring Space Agency
    European Space Agency (ESA)

    Sponsoring Organization
    Information Pending

    Research Benefits
    Information Pending

    ISS Expedition Duration
    May 2012 - September 2014

    Expeditions Assigned

    Previous ISS Missions
    Information Pending

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    Experiment Description

    Research Overview

    • The objective of the Reversible Figures experiment is to investigate whether the perception of ambiguous figures is affected by microgravity. The hypothesis is that the number of perceived reversals of perspective-based reversible figures is altered in microgravity when compared to normal gravity, but that the perceived reversal of 2D figures is not affected. Ambiguous reversible figures are seen with a statistically known preference in 1g. This hypothesis is to be verified by determining for all phases of the spaceflight: (1) the time for first reversal and the number of perceived reversals of 3D and 2D reversible figures in a given time frame; and (2) the probability for seeing each view/reversal within a figure.


    The Reversible Figures (Reversible Figures) investigation involves comparisons of pre-flight, in-flight, and post-flight perceptions with regards to ambiguous perspective-reversible figures to assess the influence of microgravity.

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    Space Applications

    It is hypothesized that the adaptive changes in the processing of gravitational information by the neurovestibular system during space flight may cause changes in 3D visual perception. Several reports indicate that the visual tracking abilities, perception, and reaction time deteriorate in crewmembers. This could have important consequences on the crew performance while in flight, including impaired psycho-motor ability, experimental error, or other various behavioral disturbances. Indeed, misperception of the environment in microgravity effects crewmember performance on sensory-motor tasks (such as operation of robotic arm), spatial orientation, and navigation. Understanding whether the perception of ambiguous figures is affected by microgravity might help taking this into account for specific tasks to be executed by humans in microgravity.

    Earth Applications

    The same alterations in 3D visual perception in weightlessness are also seen in vestibular defective patients on Earth. Disturbances in 3D visual perception may influence the ability to accurately perform perceptual-motor tasks such as those involved in grasping objects, controlling vehicles or robotic arms, and extra-vehicular activities. Thus, understanding how adaptation to changing gravity affects the way an object is perceived is relevant for both fundamental and clinical research on Earth and for human space exploration.

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    Operational Requirements
    Information Pending

    Operational Protocols

    • Pre-flight baseline data collection (BDC) is comprised of three sessions which occur in the intervals L-120 plus or minus 30 days, L-90 plus or minus 30 days, and L-60 plus or minus 30 days. The duration of each pre-flight session is 45 minutes with the minimum one day between 2 sessions.

    • In-flight, for a typical 180 day mission, the data collection includes six sessions during a two-week interval. The duration of each session is 60 minutes on a given flight day (FD), and the time range for each session should fall between between FD0 to FD15, FD16 to FD45, FD46 to FD75, FD76 to FD105, FD106 to FD135, FD136 to FD180.  Four of the sessions are mandatory (i.e., the 1st, 2nd, 4th and 6th) with a minimum of two weeks between each of these sessions. One experimental constraint that must be followed is that subjects shall be free-floating during the test portion of the sessions. Data downlink is desired after each session, and is currently planned after the last session of each test subject.

    • Post-flight data collection is comprised of three sessions occurring at R plus 1 plus or minus 1 day, R plus 4 plus or minus 2 days, and R plus 8 plus or minus 2 days (only if R plus 4 crewmember responses have not returned to pre-flight baseline values). The duration of each post-flight data collection session is 45 minutes. Note that the first post-flight session could be reduced to 30 minutes in case of time constraints or conflicts immediately after landing.

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    Results/More Information

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    Results Publications

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    Ground Based Results Publications

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    ISS Patents

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    Related Publications

      Clement G, Demel M.  Perceptual reversal of bi-stable figures in microgravity and hypergravity during parabolic flight. Neuroscience Letters. 2012; 507(2): 143-146. DOI: 10.1016/j.neulet.2011.12.006.

      Clement G, Skinner A, Richard G, Lathan CE.  Geometric illusions in astronauts during long-duration spaceflight. NeuroReport. 2012; 23(15): 894-899. DOI: 10.1097/WNR.0b013e3283594705. PMID: 22955144.

      Clement G, Bukley A, Bukley A.  Mach square-or-diamond phenomenon in microgravity during parabolic flight. Neuroscience Letters. 2008; 447(2-3): 179-182. DOI: 10.1016/j.neulet.2008.10.012.

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    Related Websites
    Erasmus Experiment Archive

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    image Figure 1: Two examples of perspective-reversible figures.
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    image NASA Image: ISS032E008594 - NASA astronaut Sunita Williams, Expedition 32 flight engineer, works on the Reversible Figures (RFx) experiment in the Columbus laboratory of the International Space Station.
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    image Example of a perspective reversible figure: a chair with seat pointing toward or away from observer. Image courtesy of PI.
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    image Example of a 2D reversible figure: a Troyan soldier's helmet and face/or a man swinging a golf club
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