Expressive Communications involve more control, with emotional decisions being made by the communicator.
Expressive (or emotional) Communications are more complex than nominal, being mediated by the areas of the brain dealing with emotion. Hence, there is more room for decision making on the part of the communicating participants.
A very common example of an expressive graded signal is the whimpering versus the snarling behaviors of animals, notably a dog.
A snarl from a dog is a warning to stay away. A less intense vocalization, such as a whimper, is a sign of submission. The dog may choose his message based upon past experiences and not instinct.
Humans too, engage in a lot of expressive graded communication. The best examples are provided in a book by Edward T. Hall on Body Language.
Notes: Click here for some additional information on Body "Language"