A professor invented a lie detecting chair. Whenever anybody sitting in it told a lie, the chair would open up and dump the liar on the floor. During an experiment, a brunette sat in the chair and the professor asked her to tell about herself.

She began, I think you are the best teacher Ive ever had.

The chair immediately dumped her on the floor.

After the brunette left in a snit, a blonde sat in the chair. The professor asked her to tell something of her life.

She began, I think –

The next thing she knew, she was sitting on the floor.