The minute karen walks into your mother-in-law's house to visit, she is struck by the strong smell of her perfume. however, after about 10 minutes, karen no longer notices the smell. this is probably the result of:

sensory adaptation

Explanation:

As when you enter a new area basically there is change of environment and the senses activate and if there will be a slight change also in the smell, and quality of air that will be noticed by the body.

After certain time is spent even in the changed environment the body starts accepting such change and accordingly after few minutes even though the smell was recognizable earlier will have no effect now.

This is called sensory adaption, that is with some time the senses adapt such change.