You can override the module attributes to customize your simulation even more.
Select the stateMachine or clipReader module from the module list (depending on what you did when setting up your agent group), then press the override button 
next to the "frameRate" attribute.
Customizing your agents
The dialog in the picture will pop up.
Select the first four rows and then type 0.5 in the "Value" field.
Hit enter or press "Set Value".
Rewind your simulation.
If you hit play now, four of your agents will be playing at half speed.
