Apple Motion 4 - Manual (Page 203)

Input
These settings in the Gestures Preferences pane control how Motion knows when your
pen movements should be interpreted as gestures.
Input Method: Lets you choose between observing the settings in your Mac OS
Preferences and your Wacom Preferences or using gestures only when a trigger is enabled.
When you set the input to require a trigger, your pen and tablet act as a mouse until you
press one of the buttons on the pen or press a modifier key. This indicates that you are
entering a gesture. Releasing the button or key returns the pen to normal mouse state.
Trigger: Sets which trigger method to be used: Pen Button 1, Pen Button 2, or the Control
key on your keyboard.
Allow gestures in the air: Lets you trigger gestures without pressing the tip of the pen
on the tablet. This option is only available when a trigger is used to activate gestures.
203 Chapter 5 Preferences