The senderObject parameter by default is a shortcut to the event.target
property in the event object. It can however be set to another object in code if you wish to keep the event object intact, but pass along other information.
Lucid passes along the senderObject to each action, but does not use or depend on it, unless you, the user decides to. You may use it instead of event.target, or you may decide to set it to another object in your code. It is provided for ultimate flexibility for power users, and as a convenient shortcut.