How do we know which way is up? Are things always exactly as far away as they seem? How do people orient themselves in time and space?
These are all questions about human perception that neuroscientist Laurence Harris asks through an interesting lens: how do astronauts self-orient in outer space, in the absence of gravity?
Harris is a professor of psychology, kinesiology, health sciences, and biology at York University’s Vision: Science to Applications (VISTA) program. From knowing which way is up, to navigating from A to B, Harris spends a lot of time thinking about how our senses work to help us self-orient and perceive our own motion through space correctly.
“Our perceptions of the world, our perceptions of our body, our perception of time and our movement through the world, is a multi-sensory construct that we make in our brains. It’s at the core of what I’m interested in,” says Harris.
Central to his work is the vestibular system: the balance organs of the inner ear that help us orient relative to gravity.
“It turns out that orientation relative to gravity underlies not just our ability to stand up, but also our ability to do any visual task,” says Harris. “For example, you need to know that everything is upright. If you were taking it for granted that everybody around here is standing upright in a certain orientation, there’s many many senses that are telling you about that information, and that’s the job of the vestibular system.”
By combining virtual reality, the microgravity of space, human centrifuges, and moving rooms, Harris replicates the sensory experiences of astronauts on the International Space Station. On the Space Station, the absence of gravity releases the vestibular system and makes it even more sensitive.
“What we want to know is whether this translates into a problem of self-motion in astronauts: whether they feel they are moving further than they really are, faster than they really are, and so forth,” explains Harris.
For instance, some astronauts have reported feeling that space seems compressed, and they misjudge distances as being smaller than they actually are. These false perceptions in zero-gravity also have important implications back on Earth.
“Many of the phenomena that astronauts experience correspond to some of the same sorts of things that we get here on Earth as a result of aging,” says Harris.
Beyond clinical applications, the accurate perception of space, distance, and speed are also important to the design and safety of everyday environments and devices, like buildings or cars. Teasing apart how our senses affect our perception in outer space illuminates the human experience everywhere.