Müller-Lyer illusion

On the next page you will begin 4 trials of a line adjustment task. On each trial you will see a horizontal line divided into two parts by a movable reversed arrowhead, like this:


Your task is to adjust the movable (middle) arrowhead so that the two segments (halves) of the horizontal line are exactly equal.

You will move the arrow back and forth by clicking on the MOVE LEFT and MOVE RIGHT buttons. Then click the FINISHED button when you are satisfied that the two halves of the horizontal line are equal.