an open container of perfume (or other scented substance, such as
vanilla) in a corner of the room. Have students raise their hand when
they first smell the scent. Or, they could quietly note the time at
which they first notice it and you can analyze the data later. You
should find that students nearest the container are the first time
notice it and it spreads outward from there.
To keep the results as honest as possible, don’t tell students where you’ve placed the container or what scent you’ve used.