Donald A. Norman

On data-limited and resource-limited processes ☆

Abstract This paper analyzes the effect on performance when several active processes compete for limited processing resources. The principles discussed show that conclusions about the interactions among psychological processes must be made with caution, and some existing assumptions may be unwarranted. When two (or more) processes use the same resources at the same time, they may both interfere with one another, neither may interfere with the other, or one may interfere with a second without any interference from the second process to the first. The important principles are that a process can be limited in its performance either by limits in the amount of available processing resources (such as memory or processing effort) or by limits in the quality of the data available to it. Competition among processes can affect a resource-limited process, but not a data-limited one. If a process continually makes preliminary results available even before it has completed all its operations, then it is possible to compute performance-resource operating characteristics that show how processes interact. A number of experiments from the psychological literature are examined according to these processing principles, resulting in some new interpretations of interactions among competing psychological processes.

Direct manipulation interfaces

Direct manipulation has been lauded as a good form of interface design, and some interfaces that have this property have been well received by users. In this article we seek a cognitive account of both the advantages and disadvantages of direct manipulation interfaces. We identify two underlying phenomena that give rise to the feeling of directness. One deals with the information processing distance between the users intentions and the facilities provided by the machine. Reduction of this distance makes the interface feel direct by reducing the effort required of the user to accomplish goals. The second phenomenon concerns the relation between the input and output vocabularies of the interface language. In particular, direct manipulation requires that the system provide representations of objects that behave as if they are the objects themselves. This provides the feeling of directness of manipulation.

Attention to Action

Much effort has been made to understand the role of attention in perception; much less effort has been placed on the role attention plays in the control of action. Our goal in this chapter is to account for the role of attention in action, both when performance is automatic and when it is under deliberate conscious control. We propose a theoretical framework structured around the notion of a set of active schemas, organized according to the particular action sequences of which they are a part, awaiting the appropriate set of conditions so that they can become selected to control action. The analysis is therefore centered around actions, primarily external actions, but the same principles apply to internal actions—actions that involve only the cognitive processing mechanisms. One major emphasis in the study of attentional processes is the distinction between controlled and automatic processing of perceptual inputs (e.g., Shiffrin & Schneider, 1977). Our work here can be seen as complementary to the distinction between controlled and automatic processes: we examine action rather than perception; we emphasize the situations in which deliberate, conscious control of activity is desired rather than those that are automatic.

Representations in Distributed Cognitive Tasks

In this article we propose a theoretical framework of distributed representations and a methodology of representational analysis for the study of distributed cognitive tasks—tasks that require the processing of information distributed across the internal mind and the external environment. The basic principle of distributed representations Is that the representational system of a distributed cognitive task is a set of internal and external representations, which together represent the abstract structure of the task. The basic strategy of representational analysis is to decompose the representation of a hierarchical task into its component levels so that the representational properties at each level can be independently examined. The theoretical framework and the methodology are used to analyze the hierarchical structure of the Tower of Hanoi problem. Based on this analysis, four experiments are designed to examine the representational properties of the Tower of Hanoi. Finally, the nature of external representations is discussed.

Simulating a Skilled Typist: A Study of Skilled Cognitive-Motor Performance.

We review the major phenomena of skilled typing and propose a model for the control of the hands and fingers during typing. The model is based upon an Activation-Trigger-Schema system in which a hierarchical structure of schemata directs the selection of the letters to be typed and, then, controls the hand and finger movements by a cooperative, relaxation algorithm. The interactions of the patterns of activation and inhibition among the schemata determine the temporal ordering for launching the keystrokes. To account for the phenomena of doubling errors, the model has only “type” schemata—no “token” schemata—with only a weak binding between the special schema that signals a doubling, and its argument. The model exists as a working computer simulation and produces an output display of the hands and fingers moving over the keyboard. It reproduces some of the major phenomena of typing, including the interkeystroke interval times, the pattern of transposition errors found in skilled typists, and doubling errors. Although the model is clearly inadequate or wrong in some of its features and assumptions, it serves as a useful first approximation for the understanding of skilled typing.

New technology and human error

This book is about the nature of human error and the implications for design of modern industrial installations. It is the first book discussing the topic from the point of view of cognitive psychology, social psychology and safety engineering. Advanced students, researchers and professional psychologists in industrial psychology/human factors and engineers or systems designers concerned with man-machine systems will find this book essential reading.

SOME PRINCIPLES OF MEMORY SCHEMATA

Publisher Summary A fundamental aspect of the structure of material contained within a large, intelligent memory system is that the contexts, in which units of the stored information are accessed, are critically important in determining the way that information is interpreted and used. Most of the schemes, currently under active consideration, can be viewed as variants of list structures or semantic network structures. This chapter discusses some implications of these memory structures in regard to how the connections among different memory units are formed and interpreted, and some of the issues of processing that arise when these memory structures are used. It also discusses the nature of memory reference processes that can lead automatically, without particular effort, to the richness of the retrievals that it is believed to be a fundamental property of human memory. When two or more processes use the same resources at the same time, they may both interfere with one another, neither may interfere with the other, or one may interfere with a second without any interference from the second process to the first. The important principle is that a process can be limited in its performance either by the amount of available processing resources, such as memory or processing effort, or by the quality of the data available to it. Competition among processes can affect a resource-limited process, but not a data-limited one.

A non-parametric analysis of recognition experiments

A non-parametric method for evaluating the results of recognition memory experiments and psychophysical detection experiments is presented. The method is based upon an ordinal analysis of recognition performance, which transforms the results of recognition tests into equivalent results for a forced-choice experiment.

Emotion & design: attractive things work better

The following is a preview of Don Normans forthcoming book, which has a working title of Emotion and Design.

Design rules based on analyses of human error

By analyzing the classes of errors that people make with systems, it is possible to develop principles of system design that minimize both the occurrence of error and the effects. This paper demonstrates some of these principles through the analysis of one class of errors: slips of action. Slips are defined to be situations in which the users intention was proper, but the results did not conform to that intention. Many properties of existing systems are conducive to slips; from the classification of these errors, some procedures to minimize the occurrence of slips are developed.