Can you take a sip of water from a
cup with your eyes closed? Will you spill the water
all over yourself? Of course not! For most of us,
this is a routine task that we don't even have to
think about. But how can you do this? Without vision,
you can't see the cup, or your hand propelling the
water to your mouth, yet you don't usually pour the
water down your shirt or in your ears. Try this simple
experiment to learn more about how you form mental
images of your body's position in space, independent
Do and Notice
this exploration, it's very important for you to keep
your eyes closed the entire time, work quickly, and
carefully observe how your body responds. So for the
best experience, either read all of the instructions
before beginning or have a friend read them to you
while you do the activity.
your eyes and raise both hands above your head.
Keep the fingers of your left hand totally still
the tip of your right index finger to the tip of
your nose, then quickly use the same finger to try
to touch the tip of your left thumb. Keep your left
hand still. Even if you "miss," go on
quickly to the next step.
touch your right index finger to the tip of your
nose and immediately use the same finger to try
to touch the tip of your left index finger.
the process three more times, each time trying to
touch a different finger on your left hand. Keep
track of how many times you succeed in touching
the tip of the correct finger. How successful were
you at finding each fingertip? Did your performance
improve with time?
repeat the activity, but this time gently wiggle
the fingers of the hand you hold in the air. Are
you more successful in touching the designated fingertip?
people are surprised to find out that they have a
difficult time touching their fingertips preciselythey
come close but don't make contact. Success usually
improves when the fingers of the target hand are wiggled
with your eyes closed, you have a sense of body positionwhere
your arms and legs are, what direction you turn your
head. This sense of body position comes primarily
from information sent to your brain by proprioceptors,
tiny sensors in your muscles, tendons, joints, and
inner ear. Proprioceptors detect stretching, elongation,
and other changes; this information is used by your
brain to create an unconscious picture of your body
and its parts in three-dimensional space. Since most
of us are highly dependent on visual cues for judging
distances and positions, proprioception alone is not
enough to give our brains the finely detailed information
needed to touch a distant body part with great accuracy.
Wiggling the fingers of the target hand increases
the success rate of finding the fingers because it
causes elongations, contractions, and tension changes
that are detected by the proprioceptors there. With
this additional information, the brain is better able
to picture the location of the target hand in space.