Romich, B.A. (1994). Knowledge in the world vs. knowledge in the head: the psychology of AAC systems. Communication Outlook, Vol. 16 No. 2, pp. 19-21.

Made available with permission from the Artificial Language Laboratory at Michigan State University.

Knowledge in the World vs. Knowledge in the Head:
The Psychology of AAC Systems

Barry Romich, P.E.

A number of years ago psychologist and cognitive scientist Donald A. Norman presented us with a book titled The Psychology of Everyday Things. In it he reviews the factors that affect our ability to use the items we encounter in our everyday lives. He relates amusing but pointed stories of people’s attempts to use VCRs, computers, slide projectors, telephones, refrigerator controls, etc.

In his book Normal distinguishes between the elements of good design for items that are encountered infrequently or used only occasionally and those with which the individual becomes intimately familiar through constant use. Items encountered infrequently need to be obvious. An example used by Norman is the common swinging door. The individual intending to pass through the door needs to know whether to push the door or pull it. We all have experienced doors where it was not obvious what to do, or two doors appeared the same, but only one would swing. However, when a door is well designed, it is obvious whether one is to push or pull. Norman refers to knowledge of how to use such items as being in the world.

However, when one uses something frequently, efficiency and speed are important, and the knowledge of how to use it needs to reside in the head. Most people can relate to the common typewriter or computer keyboard. When one uses it infrequently and has never learned to type, the knowledge of which key produces which character on the screen comes from visually scanning the keyboard and finding the key with the desired character. The knowledge comes from the world. However, people who frequently use a computer learn to touch type, transferring the knowledge to the head. Their efficiency and speed far exceed that of the hunt-and-peck typist.

Norman writes of the tradeoff between knowledge in the world and knowledge in the head. He presents a chart (Norman, 1980), excerpted here, in which he summarizes the relative merits of the properties of learning, efficiency of use, and ease of use at first encounter for both paradigms.

Knowledge in the World
Knowledge in the Head
Learning not required. Interpretation substitutes for learning. How easy it is to interpret information is the world depends upon how well it exploits natural mappings and constraints. Requires learning, which can be considerable. Learning is made easier if there is meaning of structure to the material (or if there is a good mental model).
Efficiency of use
Tends to be slowed up by the need to find and interpret the external information. Can be very efficient
Ease of use at first encounter
High Low

To summarize, knowledge in the world systems are obvious but slow and knowledge in the head systems require learning but can be fast. In augmentative and alternative communication (AAC), knowledge in the world systems are those that cannot be used without the periodic and frequent gathering of information.

For example, the person using a dynamic display system must gather new information with every input because the system changes its configuration. Word prediction systems are another example because with every letter entered a new set of choices is presented and must be interpreted. The cognitive task is actually changed several times for every item the system outputs. While this process slows the speed of operation, it also interrupts the physical and cognitive flow of language generation.

Knowledge in the head systems are those that can be used in a continuous cognitive process. Examples are those systems that use fixed codes, such as number or letter codes, abbreviations, or multi-meaning icons (MinspeakTM).

The physical and cognitive automaticity facilitated by these systems can become the cornerstone of language development. A normally developing child does not have to relearn how to say “talk” at each juncture of maturation. Rather, the automated cognitive and motor patterns, having become unconscious, support future linguistic growth.

What are the implications of these concepts for people who rely on AAC? These principles can guide both the selection and application of AAC systems. They suggest that, for people who will use an AAC system infrequently, a knowledge in the world type system might be appropriate.

However, we need to realize that communication with such a system “tends to be slowed up by the need to find and interpret the external information.” Another implication is that such a system might be recommended when it will not be possible to put knowledge in the head. Taken to the extreme, the application of such a system does not require a speech-language pathologist (SLP) or other intervention support, but limits the speed of communication.

On the other hand, if we expect frequent use of an AAC system and desire efficiency and speed, like that required for spontaneous conversation, then a knowledge in the head type system might be appropriate.
However, when such a system in recommended, training must be part of the total package. People who touch type invested in learning the skill. They either took a course in school, received other instruction, or learned on their own. Similarly, people who rely on AAC and want to communicate as fast as possible mush become familiar enough with their systems to allow this.

AAC systems must be designed to capitalize on the ability of the human mind to absorb information in particular formats. For example, meaning or semantic based codes are far easier to recall than arbitrary alphanumeric codes. The process of teaching such a system also teaches one about life and can be a positive experience for both teacher and student. Some systems address training needs with special features such as icon prediction and automatic icon reporting spelled items. Some manufacturers offer application programs for specific needs and then support them with training seminars.

While these features, functions, and services have proven valuable, they cannot substitute for the services provided by the SLP. These services are a critical component if the goal is the most effective communication possible. Just as with people who can be helped by articulation therapy, people who rely on AAC can benefit from the therapy offered by the SLP and perhaps his or her supervision of the coaching between therapy sessions.

The selection and application of an AAC system are complex multi-faceted tasks in which many factors must be considered. One of these factors is the deep significance of the tradeoff between knowledge in the world and knowledge in the head. Knowledge is the world systems can be easy to use at first encounter and can showcase the latest technology. However, it is our hope that most people who rely on AAC will communicate often. Clearly, the approach that serves the best interests of most of these people is the knowledge in the head system since it results in the fastest and most natural communication possible.

Norman, D.A. (1980). The Psychology of Everyday Things. Basic Books, Inc.: New York.

Barry Romich is an engineer and co-founder, Chairman and CEO of Prentke Romich Company ( He is co-founder of AAC Institute ( and is a member of numerous organizations with an interest in AAC. He is a member of the Medical Systems and Rehabilitation Technical Group of the Human Factors and Ergonomics Society (