In English it's common to say, "I know this town like the back of my hand!" While we may know our towns really well, how well do we actually know our hands?
Matthew Longo and his team from University College London studied the left hands of 100 people. With their hands placed palms down under a board, Longo's team gave the instruction to point to their knuckles(指关节) and fingertips with a marker pen. How did they do? Not that well.
In the experiment, according to Longo, "people think their hands are wider than they actually are. " They were most accurate when finding their thumbs, but became less accurate with each finger, up to their pinkies(小指).
"It is connected to our sense of position, " explained Longo. Humans know where different parts of our bodies are, even if we can't see them. It tells us whether a joint (关节) is straight or not. So the experiment the team conducted was to find those maps.
On the basis of the study, in our brain's map, brains "see" areas based on our sense of touch. The stronger the sense of touch in a specific body part is, the bigger that body part seems. An example is our lips. As they have more nerves than our noses, our brain's map shows our lips are bigger. If you've ever had something stuck in your teeth, it probably feels huge! That's because our tongues also have lots of nerves.
A. More nerves, larger a body part seems.
B. Let's see how our humans know our body parts.
C. It's essential to the sizes and shapes of our body.
D. Maybe not quite as well as we think, said a scientific study.
E. The same can happen with body parts having a lot of nerves.
F. They also thought their fingers were shorter than their true lengths.
G. Our brains know the body sizes and shapes from the maps they make for themselves.
