The Interaction of Internal and External Information in a Problem-Solving Task

In these studies I examine the role of distributed cognition in problem solving. The major hypothesis explored is that intelligent behavior results from the interaction of internal cognition, external objects, and other people, where a distributed cognitive task can be represented as a set of modules, some internal and some external. The Tower of Hanoi problem is used as a concrete example for these studies. In Experiment 1 I examine the effects of the distribution of representations among internal and external modules on problem-solving behavior. Experiments 2A and 2B focus on how the nature and number of rules affect problem-solving behavior. Experiment 3 investigates how a group’s problem-solving behavior is affected by the distribution of representations among the individuals. The results of all studies show that distributed cognitive activities are produced by the interaction among the representations in the modules involved in a given task: between internal and external representations and between internal representations. External representations are not peripheral aids. They are an indispensable part of cognition. Two of the factors determining the performance of a distributed cognitive system are the structure of the abstract task space and the distribution of representations across modules. INTRODUCTION The traditional approach to cognition in general and problem solving in particular focuses on an individual’s internal mental states. In the traditional view, representation and cognition are exclusively the activity of an internal mind. External objects, if they have anything to do with cognition at all, are at most peripheral aids. The cognitive properties of a group are solely determined by the structures internal to the individuals. There is no doubt that internal factors are important to cognition. They are not, however, the whole story. Much of a person’s intelligent behavior results from interactions with external objects and with other people. External and social factors also play critical roles in cognitive activities. Recently, cognitive scientists have started to address “distributed cognition,” the study of how cognitive activity is distributed across internal human minds, external cognitive artifacts, groups of people, and across space and time (Hutchins, 1990, in preparation; Hutchins & Norman, 1988; Norman, 1988, 1989, 1990). In the study of cognitive artifacts, Norman (1990) argues that artifacts not only enhance a person’s ability to perform a task, but they also change the nature of the task. In the study of the social organization of distributed cognition, Hutchins (1990) shows that social organizational factors often produce group properties that differ considerably from the properties of individuals. In this paper, I develop a framework, the modularity of representations, to analyze a set of distributed cognitive tasks, and to explore the interactions among internal and external representations and among members of a group of people. I show that external objects are not simply peripheral aids— they provide a different form of representation. External representations are interwoven with internal representations to produce distributed cognitive activities. In addition, the share of knowledge among a set of modules is important for a system’s performance. Modularity of Representations The basic principle to be explored is that the representational system for a given task can be considered as a set, with some members internal and some external. Internal representations are in the mind, as propositions, mental images, or whatever (e.g., multiplication tables, arithmetic rules, logic, language, etc.). External representations are in the world, as physical symbols (e.g., written symbols, beads of an abacus, etc.) or as external rules, constraints, or relations embedded in physical configurations (e.g., spatial relations of the items in a table, spatial configurations of the digits on a piece of paper, physical constraints in an abacus, etc.). The representations discussed in this paper are representations for tasks. In this sense, we can speak of not only internal representations, which have their traditional meaning, but also external representations. For example, an external representation can represent the external part of the structure of a task. Generally, there are one or more internal and external representations involved in any task. Each representation is a relatively isolated functional unit in a specific medium. I call this unit, whether internal or external, a module. Figure 1 shows a representational system for a task with two internal and two external modules. Each internal module resides in a person’s mind and each external module resides in an external medium. The representations of internal and external modules involved in a given task together form a distributed representation space mapped to a single abstract task space that represents the properties of the problem. Each module sets some constraints on the abstract task space. The distributed representation space plays an important role in the studies reported here. The distributed cognition perspective demands the decomposition of the abstract task space into its internal and external components, because many cognitive tasks are distributed among internal and external modules. In the traditional studies of problem solving, many abstract task spaces having internal and external components were mistakenly treated as solely internal task spaces. Generally speaking, the abstract task space of a task is not equivalent to its internal task space.