Personality and Motivation- Introduction

Donald Broadbent's career has been an exception to the rule that serious cognitive psychologists should treat individual differences as nuisance variables to be ignored. Donald has recognized the complexities of individual differences, has commented about the messiness of the findings relating individual differences to performance, but none-the-less has insisted that a proper understanding of human information processing needs to take into account individual differences in personality and motivation. For this, as well as the many other accomplishments discussed in the chapters in this book, he is to be admired.

In this chapter I review some of the historical and current evidence showing that Donald's concern for individual differences has been well founded. I emphasize how individual differences combine with situational manipulations to affect the availability and allocation of cognitive resources. More importantly, I argue that personality effects can be understood in terms of differences in the way and in the rate at which parameters of the cognitive control system are adjusted to cope with changes in a constantly varying world. I conclude with the suggestion that an analysis of the motivational states that result from the interaction of individuals with their environment improves models both of cognitive performance as well as theories of personality.[1]

When reviewing current research it is somewhat disheartening to realize that although many of the questions about individual differences were first raised in Perception and Communication (Broadbent, 1958) and discussed later in Decision and Stress (Broadbent, 1971), after three decades we have not made much progress on finding answers to these questions. There has been some progress, however, in determining the motivational states and individual differences most associated with efficient performance.[2]

Broadbent's primary observation about individual differences was that "It has been noticed many times that some individuals show larger decrements from prolonged work than others do." (Broadbent, 1958, p 140). Who are these people and what causes these decrements was and remains an important question. A subsequent question is whether there are reliable individual differences in performance decrements associated with other stressful conditions.

In general, decrements from optimal performance may be understood in terms of motivational effects (e.g., Anderson, 1990; Blodgett, 1929; Broadhurst, 1959; Hebb, 1955; Hockey, Gaillard & Coles, 1986; Humphreys and Revelle, 1984; Revelle, 1987, 1989; Sanders, 1983, 1986; Yerkes and Dodson, 1908). Motivation is the vital link between knowing and doing, between thinking and action, between competence and performance. Theories of motivation explain why rats solve mazes faster when hungry than well fed, why bricklayers lay more bricks when given harder goals than easier ones, why assistant professors write more articles just before tenure review than after, and why people choose to be fighter pilots rather than dentists. How to motivate employees to produce more widgets and how to motivate oneself to do onerous tasks are the subjects of many management and self help courses.

Fundamental questions of motivation are concerned with the direction, intensity, and duration of behavior. Within each of these broad categories are sub-questions such as the distinctions between quality and quantity, effort and arousal, and latency and persistence. Cutting across all these questions are the relative contributions of individual differences and situational constraints to the level of motivation and of subsequent performance.

Individual differences in motivation and performance may be analyzed at multiple, loosely coupled, levels of generality (Figure 1). These levels reflect the time frame over which behavior is sampled. Over short time periods (e.g. the milliseconds of an evoked potential study), situational constraints are extremely important. As the sampling frame is increased (e.g., to the seconds of a reaction time study), energetic components of motivation as well as strategic tradeoffs of speed for accuracy become more important. At somewhat longer sampling frames (e.g. the tens of minutes of a typical psychology experiment), individual differences and situational demands for sustaining performance take precedence. At even longer intervals, differential sensitivities to positive and negative feedback affect task persistence and choice. At much longer intervals, individual differences in preference affect occupational choice and the allocation of time between alternative activities. At all of these levels it is possible to distinguish between effects related to resource availability and to resource allocation. Although an adequate theory of motivation and performance should explain behavior at all of these levels, motivational effects at intermediate time frames have been most frequently examined. In particular, the focus of this chapter are those motivational effects that can affect the link between thinking and doing within periods of several minutes to several hours.

1) Levels of analysis and the psychological spectrum. Psychological phenomena occur across at least 12 orders of temporal magnitude. Cognitive and motivational theories at each frequency make use of directional and energetic constructs. Outcome measures may be organized in terms of their temporal resolution as well as their physiological emphasis. (Adapted from Revelle, 1989).

For psychologists concerned with linking cognition to action, it is essential to consider how motivational variables affect the competence-performance relationship. Ever since Blodgett's (1929) demonstration that well fed rats will learn mazes but that only hungry rats will show their knowledge by running rapidly through the maze, psychologists have been aware that competence is a necessary but not sufficient determinate of performance. An even more important study was Yerkes and Dodson's demonstration (1908) that motivational intensity (induced by foot shock) has a non-monotonic affect upon rates of learning a discrimination task and that task difficulty interacts with intensity.

Unfortunately many cognitive psychologists pay only lip service to the competence-performance distinction and will report that their subjects are well motivated and thus it is not necessary to worry about motivation. For such researchers, motivation is a nuisance variable that can be ignored by increasing sample size. The possibility that individual differences in personality might interact with situational manipulations in ways that can completely obscure important relationships is so foreign as to not even be considered.

An exception to this rule is those who have worked with or been inspired by Donald Broadbent. The best work on the effect on cognitive performance of non-cognitive manipulations such as noise, time of day, distraction, and incentives has been done by those who have followed the traditions established at the Applied Psychology Unit in Cambridge and continued at Oxford. Discussing motivational and stress effects before such a group is equivalent to bringing coals to Newcastle.

The emphasis of much of the work at the APU has been how stressors combine to affect performance[3]. Within this tradition, there has been great concern with the similarity and differences between the effects of different stressors. So, for example, while the effect of sleep deprivation is to hinder certain tasks, and noise to hinder other tasks, the combination of the two stressors can be shown to facilitate performance. An explanation that subsumes both effects is then proposed, tested and accepted or rejected (Broadbent, 1971).

This logic can equally well be applied to the combination of stressors with dimensions of individual differences. By appropriate analysis of the similarities and differences of effects due to experimental manipulations and individual differences it is possible to evaluate the construct validity of both. Certain individual differences seem to parallel certain stress manipulations while other stressors seems to affect different individuals in different ways. Both patterns of results are of theoretical importance: Parallel effects of personality and situational manipulation allow individual differences to be used to extend the effective range of experimental manipulations; different patterns for different people produce better theory by delineating the boundaries of effects of theoretical constructs.

Parallel effects of individual differences and situational stressors can suggest that both reflect differences on the same latent construct. By appropriate combinations of subject differences and of experimental manipulations, it is then possible to achieve a much greater effective range on the underlying latent construct than would be possible by manipulation or subject selection alone..[4]

There are at least three possible reactions to the observation that what improves the performance of one individual hinders the performance of another: 1) ignore that particular manipulation because it does not have consistent effects; 2) run more subjects in the hope that error terms will be reduced; or 3) ask what are the special characteristics of the different kinds of subjects. It is this third approach that is most useful. Understanding how manipulations differ across people leads to better theories of those manipulations as well as better theories of individual differences in personality. [5] More