Even with our eyes closed, we have a sense of body position—where our arms and legs are, for example, and that we are moving them. Muscles, tendons, joints, and the inner ear contain proprioceptors, also known as stretch receptors, which relay positional information to our brains. Our brains then analyze this information and provide us with a sense of body orientation and movement.
Activity 1: Find your fingertips
Close your eyes and raise both hands above your head. Keep the fingers of your left hand totally still (no wiggling!). With your right hand, quickly touch your index fingertip to your nose, then quickly touch the tip of your thumb of your left hand with the tip of your right index finger. Quickly repeat the entire process while attempting to touch each fingertip (always return to your nose in between fingertip attempts).
Switch hands and try again. How successfully did you locate each fingertip? Did you improve with time? Was there a difference when you used your right versus your left hand?
Try again, but this time, wiggle the fingers of your raised hand while you're doing this.
Activity 2: X marks the spot
Hold a piece of paper against a table top with one hand and hold a pencil in the other. Mark an X on the paper. Next, raise your pencil hand above your head, close your eyes, and make a dot on the paper as near to the X as possible. Open your eyes and check your success. Raise your hand above your head, close your eyes, and attempt to make a dot closer to the X. Do this several times. Finally, repeat with your eyes open.
Activity 3: Handwriting analysis
On a lined sheet of paper, write the word "proprioception". Place your pencil on the same line next to the written word, close your eyes, and write "proprioception" again. Is there a difference in the appearance of the two written words?
In all of these activities, you are using proprioceptors in your muscles, tendons, and joints to judge your body's position. Since most of us are highly dependent on visual cues for judging distance, position, etc., proprioception alone is not enough to give us the fine detail of position needed to complete these activities accurately. Wiggling your fingers in the first activity provides additional information to your brain, which helps you correctly locate your fingers in space.
You may notice that with repeated trials you can learn to complete the activities more successfully. Visual cues, such as looking at the position of the X between trials, can also help you adjust your movements to complete the task at hand. This is less applicable to the handwriting activity—most people find that vision is not an important cue in reproducing written words, because we're used to the "feel" of writing provided by proprioceptors in our hands and fingers.
This Science Snack is part of a collection that highlights Black artists, scientists, inventors, and thinkers whose work aids or expands our understanding of the phenomena explored in the Snack.
Dr. Patricia Cowings (1948- present), pictured above, is a psychophysiologist who trained as an astronaut at NASA, and was an alternate to go into space in 1979. Interested in human potential, she researched and developed individually tailored protocols to prevent motion sickness in astronauts. Her Autogenic Feedback Training Exercise has been used widely. Dr. Cowings is the Principal investigator of Psychophysiological Research Laboratories at NASA Ames Research Center.