You cannot do two things at once

[andrewducker]

While sitting at your desk make clockwise circles with your right foot.

While doing this, draw the number "6" in the air with your right hand.

Your foot will change direction.

Comments

[garthmyl.livejournal.com]

it also works if you make anti-clockwise circles with your left foot and make a figure 9 with your right hand.