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Area of Science:

  • Human perception
  • Spaceflight physiology
  • Visual-spatial cognition

Background:

  • Altered gravity environments, such as microgravity, can significantly impact sensory perception, including size perception.
  • Previous research suggests changes in posture and microgravity affect visual perception, but findings on object height perception remain inconsistent.

Purpose of the Study:

  • To investigate how changes in posture and long-term microgravity exposure influence the visual perception of object height.
  • To assess if these perceptual biases are associated with changes in judgment precision.
  • To explore potential sex/gender differences in these perceptual alterations.

Main Methods:

  • Astronauts (n=12) and Earth-bound controls (n=20) performed a virtual object size matching task in a simulated corridor.
  • Astronauts completed the task before, during, and after extended International Space Station (ISS) missions, in both upright and supine postures.
  • Controls simulated microgravity by lying supine, with sessions spaced to mirror astronaut testing schedules.

Main Results:

  • No immediate effect of microgravity on perceived object height was detected.
  • Astronauts consistently underestimated object height relative to a haptic reference, with estimates significantly smaller 60+ days post-return.
  • No significant differences in judgment precision were observed; control participants showed a posture-dependent effect only in initial sessions.

Conclusions:

  • No immediate countermeasures are needed for microgravity's acute effects on object height perception.
  • Space travelers should be informed about potential late-emerging and persistent changes in visual perception skills.
  • Posture-dependent effects, potentially related to simulated eye height, may offer a unifying explanation for observed perceptual shifts.