Why do you get used to a smell after a while? Even a few seconds later?

Question

For example, the Hamadrayas Baboon exhibit at the zoo smelt absolutely god awful, but I had to approach to write about my observations for biology. Then, after about thirty seconds, I couldn't smell anything, even though I knew better than to assume that the babboons just stopped stinking.

Answer 1

Fatigue or desensitization. The sense of smell acts as a warning sign (as does sound and site). If you are exposed to an awful smell (such as your baboon) and you choose to ignore it, your body soon tires of sending the "this stinks, lets get away message" and you literally do not "smell" it any more. Just like having a ticking alarm clock by your bed. The first night all you here is tick,tick,tick,but soon you don't notice until it stops. But if you are exposed to a chemical that 'numbs' your sense of smell, well then that is self explanitory. case in point. Hydrogen Sulfide, that rotten egg smell, will desensitize your sense of smell. H2S is toxic and you die if you breath it. People (in mines for example) because they would smell H2S "Oh no lets get out of here" and then say "never mind I don't smell it anymore", and die. So if you smell or don't smell something it is because you choose not to (baboon) or you can't (h2s). There is more to smelling than just your nose.

Answer 2

Your brain "gets used to" it and starts to ignore it.

Another example with smell: you put on perfume in the morning and you can smell it, but by the end of the day you probably forgot you even had it on.

With sight (this is really cool, try it out sometime!):
Look at some really bright colored things (it can be anything but bright colors are the neatest) without moving your eyes or blinking. Your whole field of view will turn to grey after a little while.

Answer 3

Your brain (or the higher concious part anyway) focuses its attention on things that are out of the ordinary. Once it has them "figured out" they don't rise to the level of conciousness. The sensory neurons are still being stimulated, but this information does not travel higher up the processing chain because the higher neurons already "know" about it. A great book that explains this a lot better than I can is "On Intelligence" by Jeff Hawkins.

Answer 4

امــــــــــــــ الدموع ــــــــــــــير

Answer 5

coz you're already 'immune' to it..