Complementary Strategies: Why we use our hands when we think

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Table of Contents Abstract Keywords

Complementary Strategies: Why we use our hands when we think

Introduction Complementary Strategies A Simple Coin Counting Experiment

David Kirsh Dept. of Cognitive Science Univ. California, San Diego La Jolla, CA 92093-0515 +1 858 534-3819 [email protected]

Complementing Visual Strategies Memory

Abstract

Managing Attention

A complementary strategy can be defined as any organizing activity which recruits external elements to reduce cognitive loads. Typical organizing activities include pointing, arranging the position and orientation of nearby objects, writing things down, manipulating counters, rulers or other artifacts that can encode the state of a process or simplify perception. To illustrate the idea of a complementary strategy, a simple experiment was performed in which subjects were asked to determine the dollar value of collections of coins. In the no-hands condition, subjects were not allowed to touch the coin images or to move their hands in any way. In the hands condition, they were allowed to use their hands and fingers however they liked. Significant improvements in time and number of errors were observed when S's used their hands over when they did not. To explain these facts, a brief account of some commonly observed complementary strategies is presented, and an account of their potential benefits to perception, memory and attention.

Helping Perception Conclusion Acknowledgements References Other Articles Kirsh Home

Keywords complementary strategy, memory, attention, perception, cognition

Introduction A complementary strategy can be defined as any organizing activity which recruits external elements to reduce cognitive loads. The external elements may be our fingers or hands, pencil and paper, movable icons, counters, measuring devices, or other entities in our immediate environment. Typical organizing activities include pointing, arranging the position and orientation of nearby objects, (Kirsh, 95), writing things down, manipulating counters, rulers or other artifacts that can encode the state of a process or simplify perception. An obvious example of a complementary strategy is using pencil and paper to help add a list of several two and three digit numbers. Most of us find it easier, faster and more reliable to write down incremental sums, and carry overs, than to do the summing entirely in our heads. For long lists, we tend, as well, to recruit the pencil itself as a pointer to help keep our place. Each of these actions has its cognitive benefit. By writing down numbers we offload that portion of working memory required to store intermediate results, by pointing to particular numerals we help direct attention and offload that portion of working memory required to store knowledge of location, and by recording carry overs we set up the environment to simplify verification of our sum, should we desire to redo part of it. In my terminology, such actions complement the internal processes occurring when we add. They are external components in an interactive computation. (Hutchins, 95). It is certainly no new claim to argue that, as intelligent creatures, we have techniques for altering our environment to enhance our cognitive performance. Cognitive anthropologists, and situated activity theorists have long discussed some of the ways we have of changing our environment to augment cognition. (Lave 88). Typically, however, the changes discussed are cultural, they arise when new technologies are introduced, or when we learn new facts, methods and concepts. They take days or weeks or years to evolve, and they involve sharing resources and frequently cooperating with others. Moreover, they are rarely studied experimentally. (Kirsh & Maglio, 94) The environmental adaptations I shall focus on, however, occur moment by moment as we manage our workspaces. They are usually quick to set up, and their effect is brief, measured in seconds or fractions of seconds,. Moreover, these strategies are often

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Complementary Strategies: Why we use our hands when we think

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acquired quickly, as when, for instance, in the course of an activity, we discover the value of pointing, or laying down a ruler, etc. We often learn these by ourselves, and our improved performance can be studied both analytically and experimentally. In this paper I explore one pervasive example of such complementary strategies: using our hands to help think, remember and perceive. After briefly elaborating the central idea, I introduce a pilot experiment to explore a few of the functions served by pointing and related hand movements. I conclude with a short account of some of the principles underpinning complementary strategies.

Complementary strategies Imagine being shown an upside down photograph and asked to identify the person depicted. Your natural action is to reach out and turn the picture right side up. Faces are more readily recognized when upright. Apparently, to facilitate perception, we perform an action that adapts the world to our perceptual capacities. This idea -- that sometimes the best way to solve a cognitive problem is by adapting the world rather than adapting oneself -- lies at the heart of complementary strategies. I believe we learn these adaptational strategies by the thousands. For example, if an agent were given the task of memorizing the letters of a string, such as QIUYOKJHUYTOGU, first without touching the letters, then with touch and re-arrangement allowed, it is likely that he or she would discover a method of moving the letters to reliably increase performance. One such letter-moving technique would be to shift the letters into groupings, such as QIU YOK JHU Y TO GU. Another, more radical technique, would be to re-order the letters in alphabetical order, such as GHIJK OO Q T UUU YY. In any such activity there is a trade-off: the cost in time and effort to perform the complementary activity in the world vs. the time and effort to use existing mental procedures and strategies to accomplish the task without external aid. (Kirsh, 95). More factors are involved in the choice of a complementary strategy than just speed, however. In addition to (potentially) faster performance the virtue of such strategies is that by changing the local environment -- at the right time and in the right way -- agents are able to reduce the probable error rate, to cope with larger, more complex problems, and to deal with interference more successfully -- all typical measures of performance, and indicators of the cognitive demands a task imposes. Complementary strategies, therefore, allow agents to compensate for resource limitations in working memory and processing power, and cognitive limitations in categorizing skill, and so on. (Backman et al, 92). The objective of research on complementary strategies is to expose the ubiquity of these strategies -- particularly those that are spontaneously displayed by subjects -- to describe the key trade-offs, such as speed-accuracy, speed-problem size, speed-robustness, and to explain these in terms of an underlying processing account describing the way mental resources are used. If complementary strategies are pervasive, there ought to be general principles governing the shape of trade-off curves for successful complementation strategies.

A Simple Coin Counting Experiment To observe how complementary strategies enhance performance, a simple pilot experiment was performed. Three male and two female subjects (age 23-38, mean 26) were shown two sets of 30 images, each depicting a different arrangement of quarters, dimes and nickels. Their task was to determine the dollar and cents amount present. See figure 1. In condition one, the no hands condition, subjects were told not to point at the coin images, or to move their hands. In condition two, the hands condition, they were allowed to use their hands and fingers to point or count. They were instructed to sum the coins as quickly as possible, but to make every effort to give the correct answer. The results showing the mean time taken to announce a sum, hereafter time, and the mean number of mistaken sums, hereafter errors, are given in figure 2. On average subjects took 22.5 sec in no hands and 18.7 sec in hands to announce their answer, and they were mistaken in no hands 68% or 20.3 out of 30 stimuli, (p