motion 5.4 attractor z does not work?

Hi,

I am using Motion 5.4.3.

I am following the book Motion 5 Apple Pro Training Series by M. Spencer and ran into this problem in Chapter 3. We are supposed to use the behavior Attractor to make images on the canvas to fall into the canvas (negative z-direction). I did exactly what the book says, but those images just would not fall back in z-space. This is what I did:

1. Put all the images in a group called Photos.
2. Create a different group called 3D, put a Rectangle (from the rectangle tool) in it.
3. Set the position of the Rectangle to (0,0,-5000).
4. Drag the Attractor behavior to the Rectangle.
5. In the Inspector for the Rectangle, go to Behaviors pane, click the Z button, set Influence to 6000, set Strength to 200.

Nothing happened. So I set Affect to All Objects for Attractor in the Behaviors pane. Still, nothing happened. According to the book, the images are supposed to move back in z-space...