Coordinating the Interruption of People in Human-Computer Interaction       

                                       Daniel C. McFarlane 
					  Naval Research Laboratory, Code 5513
                              	   Washington, D.C. 20375, USA 
	                            +1-202-767-2116, mcfarlane@acm.org
  

ABSTRACT
People have cognitive limitations that make them sensitive to interruption.  These limitations
can cause people to make serious mistakes when they are interrupted.  Unfortunately, interruption of people is a
side effect of systems that allow users to delegate tasks to active background processes, like intelligent software
agents.  Delegation carries the costs of supervision, and that often includes being interrupted by subordinates.
User interfaces for these kinds of computer systems must be designed to accommodate peoples limitations relative 
to being interrupted.  A theory-based taxonomy of human interruption was used to identify the four known
methods for deciding when to interrupt people.  An experiment was conducted with 36 subjects to compare these
four different design approaches within a common context.  The results show important differences between the
four user interface design solutions to the problem of interrupting people in human-computer interaction (HCI).


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