After reviewing the literature linking threat, incentive, and relaxation to motor performance, Neiss (1988) concluded that both the construct of arousal and the hypothesis of an inverted-U relationship between performance and arousal should be abandoned. These arguments were, however, based on research that does not permit clear evaluation of either the construct of arousal or the inverted-U hypothesis. Furthermore, some of Neiss's assumptions are questionable. This article reviews evidence that provides strong support for the inverted-U hypothesis. It is concluded that the concept of arousal is pragmatically useful in organizing a broad range of behavioral data. Neiss (1988) recently presented a valuable review of the empirical literature relating threat, incentive, and relaxation to human motor performance. After considering this evidence, Neiss argued that the concept of arousal should be abandoned, along with the proposition of an inverted-U relationship between arousal and performance. Instead, Neiss advocated the study of discrete psychobiological states. Arguments against a generalized arousal concept were, however, undermined by problems with the type of data reviewed and with the assumptions made regarding the inverted-U hypothesis.Before discussing these issues, several points of agreement between the present position and Neiss 's (1988) position should be noted. First, it is agreed that motivational constructs such as arousal, anxiety, and emotion are multifaceted. Second, it is agreed that specific psychobiological states involve varying combinations of physiological, cognitive, and affective reactions. A corollary of these two statements is that all operationalizations of any of these constructs will include irrelevancies (or in Neiss's terms, side effects). Third, it is agreed that prediction of performance within any particular context will be best if based on detailed information about physiological, cognitive, affective, motivational, and individual difference influences on performance in addition to detailed information about the cognitive and motor demands of the task. That is, there will typically be an increment in predictive validity if refined models are used.The fundamental issue, however, is that of the pragmatic usefulness of general constructs such as arousal. This article addresses limitations of the type of evidence that Neiss (1988) reviewed and difficulties with Neiss's assumptions regarding arousal and the inverted-U hypothesis. Many examples are drawn from the literature on cognitive performance because research in this area has explicitly addressed the relevant con-I thank W. Revelle, T. Rocklin, and an anonymous reviewer for their helpful comments on this article.

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Impulsivity has been interpreted as a stable mediator of rate of change in arousal states. To test this hypothesis, 129 Ss differing in impulsivity were given placebo or caffeine at 9:00 a.m. or 7:30 p.m. Recognition memory was tested for the last 20 items from 2 lists of 24 items and 2 lists of 80 items. Scores from this paradigm reflect sustained attention and are thus sensitive to changes in arousal. A 4-way interaction among impulsivity, time of day, drug, and prior stimuli (p < .05) indicated that for those given placebo, recognition memory for long and late lists was poorer the higher the impulsivity in the morning; this pattern reversed in the evening. Caffeine reduced recognition errors. These results indicate that impulsivity is not a stable predictor of rate of change in arousal states. Instead, susceptibility to attentional lapses is mediated by impulsivity-related phase differences in diurnal arousal rhythms.Impulsivity is one of the dimensions of individual differences frequently identified by theorists concerned with the biological bases of personality. Although the appropriate theoretical interpretation of impulsivity is a matter of ongoing debate, many models either explicitly or implicitly posit a relationship to arousal (e.g., Barratt & Patton, 1983;H. J. Eysenck & Eysenck, 1985;Gale, 1987;Revelle, Anderson, & Humphreys, 1987;Schalling, Edman, & Asberg, 1983;Strelau, 1987;Zuckerman, 1983). Arguments that impulsivity is linked to arousal can be traced largely to Hans Eysenck (1967), who proposed that (a) there are genetically influenced differences in basal arousal levels, (b) all individuals experience maximally positive hedonic tone at intermediate arousal levels, and (c) individuals who are chronically underaroused develop patterns of behavior designed to increase their arousal. Because social, spontaneous, and risky behaviors (for example) typically afford greater arousal potential than solitary, planned, or safe endeavors, Eysenck proposed that phenotypically extraverted behavior patterns tend to develop among those whose basal arousal levels are low. This theory provided an explanatory link between evidence of the heritability of extraversion and data suggesting differences between introverts and extraverts in a variety of laboratory phenomena. We wish to thank Robert Calderon, Debra Janiszewski, Kimberly Moy, Kathryn Rosenthal, Tina Rovick, Vicky Singh, Sara Wilcox, and Peggy Wu for their assistance in collecting and scoring data.Correspondence concerning this article should be addressed to Kristen Joan Anderson, Department of Psychology, Northwestern University, Evanston, Illinois 60208.In brief, Eysenck proposed that the basal arousal level of introverts is higher than that of extraverts and, as a corollary, that the two primary subtraits of extraversion, sociability and impulsivity, are also negatively related to arousal.The term arousal is used here to refer to a state involving nonspecific physiological activation and the nondirectional component of alertness. Reflected in experience...

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Easterbrook's (1959) suggestion that arousal is inversely related to the range of cue utilization has been frequently cited as an explanation for the curvilinear relationship between arousal and performance. There is very little empirical support for this position, however. As a test of the Easterbrook hypothesis, 60 undergraduates who varied in their impulsivity level were given caffeine or placebo and then asked to proofread several passages. Estimates of sensitivity were calculated using signal detection techniques. It was predicted that high arousal would reduce sensitivity to interword errors, which require a broad range of cue utilization, but that the observed levels of arousal would not affect sensitivity to intraword errors, which require a minimal range of cue utilization. A significant crossover interaction between impulsivity and drug for interword errors indicated that caffeine increased the error detection rate of the (less aroused) more impulsive subjects but lowered the error detection rate of the (more aroused) less impulsive subjects. The results of this study support the suggestion that arousal has direct effects on the capacity for simultaneous information processing, independent of its effects on performance speed.