Science Questions

When I ride a lawnmower, it vibrates a lot. After I get off, my feet feel like they are vibrating, even though the ground below me is not vibrating. Adam Little

This is because of a quirk in the way your body processes incoming sensory information. We have a process called adaptation, where if we experience something all the time, the nervous system shuts off the sensitivity to that thing, to avoid sensory overload. For example, if you visit someone’s house, you immediately notice a smell, but after you have been there for a few minutes, you stop noticing. Our bodies are only interested in things that change, so if you are in the jungle, you would need to pay a lot of attention to the smell of smoke if it suddenly arrived. If you were constantly experiencing the smell of all the trees and soil around you, would wouldn’t be as able to pick out the smoke.

The same thing happens on your lawnmower – the vibration is there all the time while you’re mowing. The body suppresses it’s sensitivity to the vibration. When you take the vibration away, they body is suppressing something which isn’t there, and so you feel the inverse of what your nerves were trying to cancel; in this case, you feel like your feet are vibrating.

The same thing happens when you’ve been on a boat for an extended time, you get back on land and still have ‘sea legs’!

July 2007