Up (keyCode 38) and Down (keyCode 40) Keys Reversed?

Hi everybody,

I am using Adobe Flash CS4. I just took a tutorial for keyboard input, and when I test my movie, the up key causes downward motion and the down key causes upward motion.

Here is my code:

function onKeyPress(event:KeyboardEvent):void {

            if (event.keyCode==38) {

                trace("up arrow pressed");

                ball.y+=movement;

            }

            if (event.keyCode==40) {

                trace("down arrow pressed");

                ball.y-=movement;

            }

I am using a graphic called "ball" here.

Does anybody know why this is happening?

Thanks for reading