Image Reversal In Space (Iris) - 09.05.18

Overview | Description | Applications | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
Image Reversal in Space (Iris) experiment is an educational experiment developed by students at the International Space University. This experiment will study the effects of microgravity on the way people perceive two-dimensional and three-dimensional objects. The experiment and its software was designed by a multidisciplinary group of students, giving them valuable experience as they prepare to launch their own careers in space.
Science Results for Everyone
Those crazy pictures where images appear to grow smaller or larger depending on how you look at them were used to study how microgravity affects our visual perception of two- and three-dimensional objects. In microgravity, we rely less on linear cues to perceive three-dimensional objects, probably because the brain adapts to weightlessness by changing how it processes information about gravity. The experiment compared how frequently crew members changed from one perception of an image to its reverse after long-term exposure to weightlessness.  Data suggest that the reversal occurs less often during flight, perhaps because depth perception is weaker in weightlessness.

The following content was provided by Gilles Clément, Ph.D., and is maintained in a database by the ISS Program Science Office.
Experiment Details


Principal Investigator(s)
Gilles Clément, Ph.D., Lyon Neuroscience Research Center, Lyon, France

Information Pending

Information Pending

Sponsoring Space Agency
Canadian Space Agency (CSA)

Sponsoring Organization
Information Pending

Research Benefits
Information Pending

ISS Expedition Duration
April 2009 - October 2009

Expeditions Assigned

Previous Missions
ISS Expedition 19/20 was the first performance of Iris on the ISS.

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Experiment Description

Research Overview

  • The Image Reversal in Space (Iris) experiment will measure how astronauts respond to a series of optical illusions and compare their reaction time for recognizing the different images to data recorded while the crew was on Earth.

  • Iris was developed in the summer of 2008 by a number of students at the International Space University when they were charged to create a simple experiment that would be able to be performed in space. The purpose of doing this was to teach the students how to design an experiment for testing in microgravity.

There are many situations, known as illusions, which clearly demonstrate that our visual perception is less than entirely accurate. For example, when looking at a picture or a television screen, the brain assumes that we are seeing objects and spaces that have depth. As a result, we are accepting a set of signals or cues that create an illusion of three-dimensional space. The vast majority of human beings experience the same illusion, suggesting that its origin lies in the physiological mechanisms of perception.

A clear demonstration of the interpretive nature of visual perception comes from ambiguous figures (optical illusions), i.e., single images that can give rise to two or more distinct perceptions. These are two-dimensional images that are perceived as three-dimensional objects. Due to gravity constraints, some configurations are more often present than others. The Image Reversal in Space (Iris) experiment will investigate whether the perception of three-dimensional ambiguous figures is affected when the observer is in a reduced gravity environment.

In order to conduct the Iris experiment, a series of 20 to 25 obscured figures will be displayed on one of the International Space Station laptops using an interactive presentation. Some figures will be three-dimensional while others will be two-dimensional. For each figure, the astronaut-subject will be asked to identify which form they see first, and then to indicate when they recognize the second form. The time delay between the occurrence of the first and the second form will then be calculated.

Tests will be performed with Canadian Astronaut Dr. Bob Thirsk before and during the flight. The same tests will also be conducted on a population of subjects on Earth. The students hypothesized that there will be a significant difference in three-dimensional figures when observed both on Earth and in space, but not for two-dimensional figures.

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Space Applications
The Iris payload supports the objective to explore and support decisions related to human exploration as well as promoting international participation in exploration. It also supports ISS activities in terms of supporting space exploration goals with an emphasis on understanding how the space environment affects astronauts’ health, capabilities and developing countermeasures.

Earth Applications
As an educational payload, Iris provides an opportunity for students to better understand the process required in order to develop science destined for space implementation, as well as increasing their understanding of the space environment and its effects on the human physiological systems through the associated International Space University workshops.

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Operational Requirements and Protocols
Operations for Iris will be performed with a crewmember before and during the flight. The same tests will also be conducted on a population of subjects on Earth.
Subjects will be tested during free-floating while viewing 5 ambiguous, perspective-reversible figures through a lightweight headset and a finger trackball connected to a laptop. For each figure, the subjects must identify which percept they see first, and then indicate when the percept changes. Ground-based tests will be performed in 1g before and after the mission.

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Decadal Survey Recommendations

Information Pending

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Results/More Information

Information Pending

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Results Publications

    Merali T, Demel M, Thirsk RB, Clement G.  Image Reversal in Space.  Student International Space Station Experiment. 60th International Astronautical Congress, Daejeon, Republic of Korea; 2009 October 14 [Per CSA]

    Clement G, Ngo-Anh JT.  Space Physiology II: Adaptation of the Central Nervous System to Space Flight - Past, Current and Future Studies. European Journal of Applied Physiology. 2013 Jul; 113(7): 1655-1672. DOI: 1007/s00421-012-2509-3.

    Merali T, Demel M, Steinberg M, Thirsk RB, Clement G.  Image Reversal in Space.  Student International Space Station Education. Canadian Space Summit, Kingston, Canada; 2009 November 22 [Per CSA]

    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.

    Urbina D, Demel M, Kohl S, Merali T, Steinberg M, Thirsk RB, Clement G.  IRIS Experiment. Columbia Geomatics Week, Bogota, Columbia; 2009 October 29 [Per CSA]

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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.

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Related Websites
Canadian Space Agency

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image NASA Image: ISS020E017981 - Canadian Space Agency Astronaut Dr. Robert "Bob" Thirsk, Expedition 20 Flight Engineer, sets up the A31p for the Iris experiment in the Destiny Laboratory on board the International Space Station.
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image NASA Image: ISS020E017982 - Canadian Space Agency Astronaut Dr. Robert "Bob" Thirsk, Expedition 20 Flight Engineer, enters data into the A31p for the Iris experiment in the Destiny Laboratory on board the International Space Station.
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