Ecological Interface Design: Theoretical Foundations

1. Ecological Interface Design: Theoretical Foundations Vicente & Rasmussen 1992

2. Unanticipated Events • Three categories of events • Familiar and anticipated events • Unfamiliar and anticipated events • Unfamiliar and unanticipated events • Operator errors • Slips: errors in execution • Mistakes: errors in intention

3. Problem Formulation • Control Theory • Law of Requisite Variety: A complex system requires a complex controller. • Parameters of a system can be defined as a set of constraints. Physical, environmental, legal, social, etc. • A good controller requires a good model of the system. • In Interface Design • How to define a complex work domain? “Domain representation formalism”. • How to communicate the domain information to the operator? Understand cognitive mechanisms people use to handle complexity.

4. The Abstraction Hierarchy • Properties of the Abstraction Hierarchy • Each level deals with the same system, but provides different observational perspectives. • Each level has a unique set of terms, concepts, and principles. • The level selected to describe the system is chosen by the observer and based on their knowledge. • Requirements for normal functioning are defined by constraints on lower levels. Effects of lower levels on higher levels determine system state. • Moving up the hierarchy increases understanding of system goals, moving down increases understanding of system functioning. • Can be used to develop system specific representations. Provides operators with information to cope with unanticipated events and a “psychologically valid” representation for problem solving.

5. Constraints & Psychological Relevance • Because the system was built in a specific way, there are defined relationships between system variable. These relationships are system constraints. Constraints are goal-oriented; if constraints are obeyed, then the system is functioning within normal parameters. If the constraints are violated, then the system has encountered a fault. The goal of the operator becomes diagnosing with constraints have been violated and correcting them. To this end, interface design should provide the operator with all the information relevant to achieving this goal. • The goal-oriented nature of the links between hierarchy levels are a psychologically useful tool for operators when diagnosing system faults. Each level is casually linked to the one below it, not semantically. This means that navigating down the hierarchy allows for more and more specific fault diagnosis.

6. Skills, Rules, Knowledge Taxonomy • Framework for information processing. • Incoming information can be interpreted in three ways, which activate three levels of cognitive control: • Signals -> Skill-based behavior (SBB) • Signs -> Rule-based behavior (RBB) • Symbols -> Knowledge-based behavior (KBB) • People have a tendency to rely on the first two levels of cognitive control, which tend to be more efficient that people realize. Multiple examples support this idea, and interfaces should be designed to allow people to use lower level processing, but higher level processing should be supported as well. Lower level processing allows cognitive resources to be more effectively divided during a complex task. The ability of the operator to use lower levels of control is determined by skill and experience.

7. Ecological Interface Design (EID) • Three principles of EID • SBB • Higher level information should be displayed as aggregates of lower level information. The operator should also be able to act upon the display directly. • RBB • The display should provide consistent 1-1 mappings between the system constraints and information displayed. Rules based on displayed information should not change in different system states • KBB • The interface should provide an abstraction hierarchy to the operator that serves as an external mental model to facilitate problem-solving.

8. Cognitive Systems Engineering Hollnagel & Woods 1983

9. Cognitive Systems Engineering (CSE) & Man-Machine Systems (MMSs) • Understanding the cognitive aspects of a system is necessary for several reasons. • Humans are not perfectly logical and rational beings. • Increased use of automation changes the role of the human in the system. • Human error is not an inherent property of the human component but a result of a poor understanding of cognitive design.

10. Cognitive Systems • A cognitive system is a seemingly intelligent system that contains a internal representation of its environment. This internal representation allows it to make predictions, assess possible courses of action, and evaluate consequences without resorting to trial and error. • Any system that includes a human operator is a cognitive system. The human has a mental representation of the mechanical system, and the system has an image composed of assumptions about the operator. Cognitive systems engineering takes this image into account during the design phase.

11. How Are Cognitive Systems Designed? • Considering the operator as another system component is not sufficient for cognitive design. Both the operator and machine should be considered cognitive systems. • Cognitive Task Analysis • Cognitive analysis is needed early in the design process to establish the cognitive demands placed on the operator and the cognitive activities that will be placed on the MMS. The man-machine interface should support the cognitive activities of the operator. • Man-Machine Principles • Abstraction Hierarchy again. • Evaluating The Suggested Design • Checking whether the stages of the design process meet the goals in the task description. Evaluating the empirical and ecological validity of the design.