Chapter 9. Minimizing Cognitive Load

Cognition is the processing of information from the world around us. It includes perception, attention, pattern matching, memory, language processing, decision making, and problem solving. Cognitive load is the amount of mental resources needed to perform a given task.

All user interfaces make cognitive demands on users. Users must master special rules of system use, learn new concepts, and retain information in short-term memory. They must create and refine a mental model of how the system works and how they should use it. Systems that use purely auditory interfaces further challenge human memory and attention because they present information serially and non-persistently.

Successful user interface designs must respect the limitations of human cognitive processing. If a design requires the user to hold too many items in short-term memory or to learn a complex set of commands too quickly, it will fail. This chapter describes a number of guidelines for minimizing the cognitive load on users of spoken language interfaces.

There are three cognitive challenges you should consider as your design progresses:

1. Conceptual complexity: How complex are the new concepts callers must learn? How well do new mental structures match concepts and procedures that users are already familiar with?

2. Memory load: How much information must callers hold in their short-term memory? How much new material (e.g., commands, procedures) must they learn?

3. Attention: Is it easy for the caller to attend to the most salient information? Will callers' attention be divided? If they are momentarily distracted (e.g., while driving), can they seamlessly continue their interaction with the system when they are ready?

The following sections discuss each of these potential challenges and present guidelines for handling them.