Magnitude of incentive effects on heart rate

Arousal, Gray's theory of anxiety, and the etiology of psychopathy

This paper focuses on Jeffrey Gray's theory of anxiety from the perspective of Fowles' (1980) application of his work to theories of arousal, psychophysiology, and the etiology of psychopathy. Although highly influential, the concept of general arousal failed to find support in terms of between-individuals assessment with multiple physiological measures. Gray's constructs of a behavioral inhibition system (BIS) that mediates anxiety, a behavioral approach or activation system (BAS) that energizes behavior to approach rewards, and a nonspecific arousal system that energizes behavior captured aspects of arousal. Fowles (1980) proposed that the BIS elicits electrodermal activity in response to threats, the BAS increases heart rate in response to reward incentive cues, and psychopathy is associated with a weak BIS. The paper reviews Gray's impact on future research on these topics, including early proposals relevant to the National Institute of Mental Health's Research Domain Criteria. Finally, the paper summarizes the evolution of theories of the etiology of psychopathy since 1980, noting ways in which aspects of Gray's theory are still seen in psychopathy research. Patrick's triarchic model has emerged as a major theory of psychopathy. Beauchaine's trait impulsivity theory of Attention Deficit Hyperactivity Disorder also is relevant.

Is satisficing really satisfying? Satisficers exhibit greater threat than maximizers during choice overload

When selecting from too many options (i.e., choice overload), maximizers (people who search exhaustively to make decisions that are optimal) report more negative post-decisional evaluations of their choices than do satisficers (people who search minimally to make decisions that are sufficient). Although ample evidence exists for differences in responses after-the-fact, little is known about possible divergences in maximizers' and satisficers' experiences during choice overload. Thus, using the biopsychosocial model of challenge/threat, we examined 128 participants' cardiovascular responses as they actively made a selection from many options. Specifically, we focused on cardiovascular responses assessing the degree to which individuals (a) viewed their decisions as valuable/important and (b) viewed themselves as capable (vs. incapable) of making a good choice. Although we found no differences in terms of the value individuals placed on their decisions (i.e., cardiovascular responses of task engagement), satisficers-compared to maximizers-exhibited cardiovascular responses consistent with feeling less capable of making their choice (i.e., greater relative threat). The current work provides a novel investigation of the nature of differences in maximizers'/satisficers' momentary choice overload experiences, suggesting insight into why they engage in such distinct search behaviors.

Treatment for Anhedonia: A Neuroscience Driven Approach

Anhedonia, or loss of interest or pleasure in usual activities, is characteristic of depression, some types of anxiety, as well as substance abuse and schizophrenia. Anhedonia is a predictor of poor long-term outcomes, including suicide, and poor treatment response. Because extant psychological and pharmacological treatments are relatively ineffective for anhedonia, there is an unmet therapeutic need for this high-risk symptom. Current psychological and drug treatments for anxiety and depression focus largely on reducing excesses in negative affect rather than improving deficits in positive affect. Recent advances in affective neuroscience posit that anhedonia is associated with deficits in the appetitive reward system, specifically the anticipation, consumption, and learning of reward. In this paper, we review the evidence for positive affect as a symptom cluster, and its neural underpinnings, and introduce a novel psychological treatment for anxiety and depression that targets appetitive responding. First, we review anhedonia in relation to positive and negative valence systems and current treatment approaches. Second, we discuss the evidence linking anhedonia to biological, experiential, and behavioral deficits in the reward subsystems. Third, we describe the therapeutic approach for Positive Affect Treatment (PAT), an intervention designed to specifically target deficits in reward sensitivity.

Oral sucrose for heel lance enhances adenosine triphosphate use in preterm neonates with respiratory distress

Objective:

To examine the effects of oral sucrose on procedural pain, and on biochemical markers of adenosine triphosphate utilization and oxidative stress in preterm neonates with mild to moderate respiratory distress.

Study design:

Preterm neonates with a clinically required heel lance that met study criteria (n = 49) were randomized into three groups: (1) control (n = 24), (2) heel lance treated with placebo and non-nutritive sucking (n = 15) and (3) heel lance treated with sucrose and non-nutritive sucking (n = 10). Plasma markers of adenosine triphosphate degradation (hypoxanthine, xanthine and uric acid) and oxidative stress (allantoin) were measured before and after the heel lance. Pain was measured using the Premature Infant Pain Profile. Data were analyzed using repeated measures analysis of variance, chi-square and one-way analysis of variance.

Results:

We found that in preterm neonates who were intubated and/or were receiving ⩾30% FiO₂, a single dose of oral sucrose given before a heel lance significantly increased markers of adenosine triphosphate use.

Conclusion:

We found that oral sucrose enhanced adenosine triphosphate use in neonates who were intubated and/or were receiving ⩾30% FiO₂. Although oral sucrose decreased pain scores, our data suggest that it also increased energy use as evidenced by increased plasma markers of adenosine triphosphate utilization. These effects of sucrose, specifically the fructose component, on adenosine triphosphate metabolism warrant further investigation.

Evidence for effects of task difficulty but not learning on neurophysiological variables associated with effort

Learning to master a task is expected to be accompanied by a decrease in effort during task execution. We examine the possibility to monitor learning using physiological measures that have been reported to reflect effort or workload. Thirty-five participants performed different difficulty levels of the n-back task while a range of physiological and performance measurements were recorded. In order to dissociate non-specific time-related effects from effects of learning, we used the easiest level as a baseline condition. This condition is expected to only reflect non-specific effects of time. Performance and subjective measures confirmed more learning for the difficult level than for the easy level. The difficulty levels affected physiological variables in the way as expected, therewith showing their sensitivity. However, while most of the physiological variables were also affected by time, time-related effects were generally the same for the easy and the difficult level. Thus, in a well-controlled experiment that enabled the dissociation of general time effects from learning we did not find physiological variables to indicate decreasing effort associated with learning. Theoretical and practical implications are discussed.

Human and laboratory rodent low response to alcohol: is better consilience possible?

If people are brought into the laboratory and given alcohol, there are pronounced differences among individuals in many responses to the drug. Some participants in alcohol challenge protocols show a cluster of 'low level of responses to alcohol' determined by observing post-drinking-related changes in subjective, motor and physiological effects at a given dose level. Those individuals characterized as having low level of response (LR) to alcohol have been shown to be at increased risk for a lifetime diagnosis of alcohol dependence (AD), and this relationship between low LR and AD appears to be in part genetic. LR to alcohol is an area where achieving greater consilience between the human and the rodent phenotypes would seem to be highly likely. However, despite extensive data from both human and rodent studies, few attempts have been made to evaluate the human and animal data systematically in order to understand which aspects of LR appear to be most directly comparable across species and thus the most promising for further study. We review four general aspects of LR that could be compared between humans and laboratory animals: (1) behavioral measures of subjective intoxication; (2) body sway; (3) endocrine responses; and (4) stimulant, autonomic and electrophysiological responses. None of these aspects of LR provide completely face-valid direct comparisons across species. Nevertheless, one of the most replicated findings in humans is the low subjective response, but, as it may reflect either aversively valenced and/or positively valenced responses to alcohol as usually assessed, it is unclear which rodent responses are analogous. Stimulated heart rate appears to be consistent in animal and human studies, although at-risk subjects appear to be more rather than less sensitive to alcohol using this measure. The hormone and electrophysiological data offer strong possibilities of understanding the neurobiological mechanisms, but the rodent data in particular are rather sparse and unsystematic. Therefore, we suggest that more effort is still needed to collect data using refined measures designed to be more directly comparable in humans and animals. Additionally, the genetically mediated mechanisms underlying this endophenotype need to be characterized further across species.

The heart contracts to reward: monetary incentives and preejection period

Wright's (1996) integration of motivational intensity theory (Brehm & Self, 1989) and Obrist's (1981) active coping approach predict that cardiovascular reactivity in active coping depends on the importance of success when task difficulty is unclear. Despite the support for this perspective, one of the basic hypotheses-the mediation of these effects by beta-adrenergic activity-has not been tested yet. To close this gap, participants worked on a delayed-matching-to-sample task and could earn either 1, 15, or 30 Swiss Francs for a successful performance. Results showed that preejection period reactivity-an indicator of beta-adrenergic impact on the heart-increased with increasing incentive value. Thus, this experiment closes a gap in the support of Wright's model by demonstrating that beta-adrenergic reactivity is associated with incentive value under conditions of unclear difficulty.

Autonomic activation associated with ethanol self-administration in adult female P rats

The present study examined changes in heart rate (HR) prior to and during limited access ethanol drinking in adult female P rats. P rats were implanted with radio-telemetric transmitters to measure HR. Daily testing involved a 90-min pre-test period (water only available) and a subsequent 90-min test period [either water (W) or ethanol available]. After a week of habituation, one ethanol group had access to ethanol for 7 weeks (CE), and another ethanol group had access for 4 weeks, was deprived for 2 weeks and then had access for a final week (DEP). Analyses of HR revealed that CE and DEP rats had significantly higher HR than W rats during test periods that ethanol was present and that DEP rats displayed higher HR during the early test period of the ethanol deprivation interval, as well. These data indicate that ethanol drinking induces HR activation in adult female P rats, and that this activation can be conditioned to the test cage environment, paralleling reports on contextual conditioning and cue-reactivity in alcoholics exposed to alcohol-associated stimuli. Therefore, this behavioral test may prove advantageous in screening pharmacotherapies for reducing craving and relapse, which are associated with cue-reactivity in abstinent alcoholics.

Incentive value, unclear task difficulty, and cardiovascular reactivity in active coping

An experiment with 44 participants assessed the moderating effects of four levels of incentive value on cardiovascular responses in active coping. Randomly assigned to one of four different incentive conditions, participants performed a memory task without knowing its difficulty in advance. By means of successfully performing the task participants could either win no reward, 10 Swiss Francs, 20 Swiss Francs, or 30 Swiss Francs. In accordance with the theoretical predictions derived from motivational intensity theory, reactivity of systolic blood pressure and heart rate monotonically increased with incentive value. Thereby, these findings provide additional empirical evidence for the predictions of motivational intensity theory with regard to unclear task difficulty and extend recent research (Richter, M., Gendolla, G.H.E., 2006. Incentive effects on cardiovascular reactivity in active coping with unclear task difficulty. Int. J. Psychophysiol. 61, 216-225.), which was not conclusive regarding the predicted monotonic relationship between incentive value and cardiovascular reactivity under conditions of unclear task difficulty.

Effects of Conditioned Reward and Nonreward Cues on the Heart Rate Response to Alcohol Intoxication in Male Social Drinkers

BACKGROUND

An exaggerated heart rate (HR) increase following alcohol intoxication has been suggested to reflect sensitivity to alcohol-induced reward. The goal of this study is to verify whether pairing alcohol ingestion with conditioned reward and nonreward cues can influence HR responses to alcohol in previously identified individuals with a low and a high HR response.

METHODS

Fifty-six male social drinkers participated in a 2-day study. On day 1, participants consumed 0.75 g/kg of body weight of pure ethanol. A median split of the alcohol-induced HR responses identified groups of low and high HR responders. On day 2, both groups participated while sober in a computer task where distinct auditory and visual cues were paired either with monetary reward or no monetary reward. Subsequently, participants were randomly assigned to an alcohol challenge, which occurred while they were exposed to either the conditioned cues of reward or to the nonreward cues.

RESULTS

The physiological response to alcohol intoxication on day 2 was compared with alcohol-induced HR responses on day 1 (neutral alcohol challenge) for both low and high HR responders. Paired t-tests showed that high HR responders had significantly decreased alcohol-induced HR responses on day 2 in the nonreward condition when compared with day 1. No other relationships between cardiac responses to alcohol and cue conditions were obtained.

CONCLUSIONS

The rewarding nature of alcohol can be altered by the context in which it is consumed in a subset of individuals who are sensitive to alcohol's stimulating properties.

Incentive effects on cardiovascular reactivity in active coping with unclear task difficulty

Two experiments with a total of 96 participants assessed cardiovascular response in active coping. The studies were run in 2x2 designs and manipulated the clarity of task difficulty (clear vs. unclear) and incentive value (low vs. high) of a memory task, which was either easy (Experiment 1) or extremely difficult (Experiment 2). In accordance with the theoretical predictions of motivational intensity theory [Brehm, J.W., Self, E.A., 1989. The intensity of motivation. Annu. Rev. Psychol. 40, 109-131; Wright, R.A., 1996. Brehm's theory of motivation as a model of effort and cardiovascular response. In: Gollwitzer, P.M., Bargh, J.A. (Eds.), The Psychology of Action: Linking Cognition and Motivation to Behaviour, Guilford, New York, pp. 424-453], systolic reactivity varied directly with incentive value when task difficulty was unclear. In contrast, when task difficulty was clear, incentives had no influence and cardiovascular reactivity was low. These findings provide the first evidence for the predictions of motivational intensity theory with regard to unclear task difficulty and complete past research that has focused on the effects of fixed and unfixed task difficulty on cardiovascular reactivity.

Heart Rate Response to Alcohol and Intoxicated Aggressive Behavior

BACKGROUND

This study examined the elevated heart rate (HR) response to alcohol intoxication, thought to reflect an increased sensitivity to alcohol-induced reward, as a potential factor in the increased likelihood of alcohol-induced aggression.

METHODS

Three groups, intoxicated high (n=37) and low (n=37) HR responders and sober controls (n=73), participated in a laboratory measure of physical aggression, the Taylor Aggression Paradigm.

RESULTS

Results revealed that intoxicated high HR responders were more aggressive than the intoxicated low HR responders and sober controls.

CONCLUSIONS

These findings are interpreted within a hypothetical model relating increased alcohol-induced aggression to a dysregulation in the motivational system responding to rewards.

Vigilance to a persisting personal threat: unmasking cardiovascular consequences in adolescents with the Social Competence Interview

We report the first systematic study of hemodynamic responses to the Social Competence Interview, using the original Ewart protocol, which focuses attention on a persisting personal threat. Physiologic changes in 212 African American and Caucasian urban adolescents during the Social Competence Interview, mirror tracing, and reaction time tasks showed that the Social Competence Interview elicits a pronounced vasoconstrictive response pattern, with diminished cardiac activity, that is more typical of alert mental vigilance than of active coping. This pattern was observed in all race and gender subgroups. Results suggest that the Social Competence Interview may be a broadly useful procedure for investigating the role of threat-induced vigilance in cardiovascular and other diseases.

BIS-BAS sensitivity and cardiac autonomic stress profiles

This study examined the relationship of sensitivities of Gray's behavioral inhibition system (BIS) and behavioral approach system (BAS) to cardiac autonomic stress responses during laboratory tasks among 65 healthy men (n=34) and women (n=31) aged 22-37 years. Carver and White's BIS-BAS scales were used to measure BIS and BAS sensitivities. We measured heart rate (HR), respiratory sinus arrhythmia, and preejection period during mental arithmetic, a reaction time task, and a speech task. Results revealed that BAS sensitivity was related to HR reactivity and parasympathetic withdrawal during the tasks, but was unrelated to baseline levels. BIS sensitivity was unrelated to both reactivity and baseline levels of all measures. Overall, our results suggest that the relationship of the BAS with cardiac reactivity seems to be mediated by the parasympathetic nervous system.

Is ADHD a disinhibitory disorder?

Attention deficit hyperactivity disorder (ADHD) is widely theorized to stem from dysfunctional inhibitory processes. However, the definition of inhibition is imprecisely distinguished across theories. To clarify the evidence for this conception, the author relies on a heuristic distinction between inhibition that is under executive control and inhibition that is under motivational control (anxiety or fear). It is argued that ADHD is unlikely to be due to a motivational inhibitory control deficit, although suggestions are made for additional studies that could overturn that conclusion. Evidence for a deficit in an executive motor inhibition process for the ADHD combined type is more compelling but is not equally strong for all forms of executive inhibitory control. Remaining issues include specificity to ADHD, whether inhibitory problems are primary or secondary in causing ADHD, role of comorbid anxiety and conduct disorder, and functional deficits in the inattentive ADHD subtype.

Mood state and cardiovascular response in active coping with an affect-regulative challenge

We investigated the impact of mood states and task valence on cardiovascular reactivity in active coping. According to previous research, subjective demand is higher in a negative mood than in a positive mood, and cardiovascular adjustments are a function of subjective demand. Thus, we expected stronger cardiovascular reactivity in a negative mood than in a positive mood during task performance. University students (n=60) were first induced into either a positive or negative mood state via exposure to music. They then performed either a pleasant or unpleasant scenario completion task that provided opportunities for mood regulation. No effects were found on cardiovascular reactivity during the mood inductions. However, during task performance, systolic and diastolic blood pressure reactivity was stronger in a negative than in a positive mood. Task valence, which was successfully manipulated according to a verbal manipulation check, and post-performance mood changes had no significant impact. Results are interpreted as a further demonstration of the impact of mood valence on cardiovascular reactivity in active coping.

Vigilance, active coping, and cardiovascular reactivity during social interaction in young men

This study of 72 undergraduate men examined the effects of two determinants of cardiovascular response-active coping and vigilance-on blood pressure and heart rate responses to social stressors. Observation of a future debate partner (i.e., vigilance) evoked larger increases in blood pressure than did observation of a less relevant person, apparently through the combination of increases in cardiac output and vascular resistance. Preparation and enactment of efforts to exert social influence (i.e., active coping) evoked heightened blood pressure and heart rate responses through increased cardiac contractility and output. Thus, both vigilance and active coping in social contexts increased cardiovascular reactivity, but apparently through different psychophysiological processes.

Psychophysiological response of ADHD children to reward and extinction

In this study, we examined heart rate and skin conductance levels of 18 children with attention-deficit hyperactivity disorder (ADHD) and 18 normal children as they performed a repetitive motor task during reward and extinction conditions. Fowles (1980, Psychophysiology, 17, 87-104; 1988, Psychophysiology, 25, 373-391) suggested that psychophysiological responsivity reflects activity in two of Gray's (1982, The neuropsychology of anxiety, Oxford University Press; 1987, The psychology of fear and stress, Cambridge University Press) motivational systems; heart rate reactivity during reward reflects activity in the behavioral activation system, and skin conductance reactivity during extinction reflects activity in the behavioral inhibition system. As predicted, control children showed increased heart rate when reward was present and increased skin conductance when reward was removed. Compared with controls, ADHD children failed to show increased skin conductance levels during extinction, suggesting a weak behavioral inhibition system. ADHD children also displayed faster heart rate habituation to reward.

Social determinants of cardiovascular reactivity: effects of incentive to exert influence and evaluative threat

The effects on cardiovascular reactivity of incentive to influence the judgements of the experimenter and the threat of social evaluation were examined in a sample of 60 male and 60 female undergraduates. Participants either were guaranteed $5.00 to prepare and deliver a brief speech or were told that the money was contingent on an evaluation by the experimenter. Participants believed that their speech would be rated for either simple clarity or verbal intelligence. The contingent incentive increased systolic blood pressure reactivity by 6.5 mmHg (32%). Evaluative threat increased systolic reactivity by 7.1 mmHg (36%). These interpersonal processes could increase the risk of cardiovascular disease and are likely to affect the degree of cardiovascular reactivity in laboratory studies.

Interactive effects of difficulty and instrumentality of avoidant behavior on cardiovascular reactivity

College-aged subjects performed 35 trials of an easy or difficult digit-recognition task. Half were told that a good performance would ensure a high chance of avoiding a blast of noise, and half were told that a good performance would ensure a low chance of avoiding the noise. Results indicated that heart rate and systolic blood pressure reactivity were higher in the difficult condition than in the easy condition only when the probability of avoiding the noise (given success) was high. When the probability of avoiding the noise (given success) was low, heart rate and systolic responsivity were low regardless of task difficulty. It also was found that (1) performance quality was poorer overall among difficult subjects than among easy subjects, and (2) that the difference in performance quality between the easy and difficult groups was somewhat (not significantly) greater in the low-probability conditions than in the high-probability conditions. Major findings are considered in terms of Obrist's reasoning regarding the psychophysiological consequences of active coping and a motivational model by Brehm, which specifies conditions under which individuals will be more and less task engaged.

Paranoid-nonparanoid differences--psychophysiological parallels

It was predicted that the psychological differences between paranoids and nonparanoids would be parallelled by differences in psychophysiological responses to stimuli varying along both informational and motivational dimensions. Skin conductance and heart rate responses to stimuli in a guessing task were measured in a group of paranoid patients and compared with those from non-paranoid and non-patient controls. A group of nonschizophrenic patients on phenothiazine medication served as drug-matched controls. Skin conductance level, response frequency and amplitude data are reported; heart rate response changes were examined by means of times series analysis and reported as first and second deceleration and first and second acceleration components. It was predicted that paranoid patients would show a greater increase in skin conductance measures with cognitive demand, and an increase in acceleratory components of the heart rate to increases in motivational variables. The normal pattern of greater electrodermal responding to the negative stimuli than the positive, and greater heart rate acceleration to the positive stimuli but not the negative (Fowles, 1980) was predicted to be reversed in schizophrenic patients, and possibly more marked in paranoids. Cognitive manipulations showed the predicted increase in electrodermal and heart rate responding in normal controls. The paranoid subjects showed a similar increase as a function of task demands, but there was no significant difference between the other groups. Motivational manipulations produced increased skin conductance responding and increases in heart rate acceleration components in normal controls, this was not parallelled in the patient groups. All subject groups failed to show greater electrodermal activity to negative than to positive stimuli. Normal controls showed significant heart rate acceleration to positive as compared to negative stimuli, this pattern was reversed in paranoid patients.

Active-passive coping and skin conductance and heart rate changes

Sixty subjects were administered 33 tasks, selected from the Raven Progressive Matrices, in conditions that differed by type of monetary reinforcement (reward, frustration, and control group). Subjects were tested in pairs. One subject, assigned as the active one, was asked to solve a problem while the other was only a passive observer. Heart rate level and the amplitude of evoked skin conductance responses were measured. Statistical analysis detected a higher heart rate level in active versus passive subjects at the beginning stage of the experiment, as well as a faster heart rate decrease in the former versus the latter group during subsequent blocks of four tasks. Changes in skin conductance response magnitude during the ensuing task phases exhibited a descending trend in passive subjects and an ascending trend in active subjects. The monetary reinforcement manipulation was not effective. The results support a concept put forward by Fowles (1988), who maintained that tonic heart rate and skin conductance response amplitude may serve as indices of the behavioral activation system and behavioral inhibition system, respectively, as postulated by Gray's model of arousal.

Interpersonal influence as active coping: effects of task difficulty on cardiovascular reactivity

This study examined the effects of attempting social influence on cardiovascular reactivity. Subjects were randomly assigned to a noncontingent reward condition or one of three conditions in which receipt of a monetary reward was contingent on their ability to influence another individual through a persuasive communication. In the contingent conditions, the task was presented as either easy, difficult, or very difficult. Measures of systolic blood pressure, diastolic blood pressure, and heart rate were recorded while subjects prepared and delivered the persuasive communication (contingent conditions) or reviewed and read aloud the same statement without an incentive to influence. The contingent conditions produced significantly higher levels of systolic and diastolic blood pressure and heart rate reactivity during preparation and speaking. Further, reactivity was higher in the difficult condition than in the easy and very difficult conditions. The findings are discussed in terms of an interpersonal equivalent of traditional active coping tasks.

Win some, lose some: parental hypertension and heart rate change in an incentive versus response cost paradigm

Fowles (1983), citing evidence from separate studies, suggests that both incentive and response cost paradigms increase heart rate and should be subsumed under Gray's (1975) 'appetitive motivational system'. Shock avoidance and loss of reward (response cost) contingencies, while aversive, appear to evoke this motivational system; consequently both should elicit heart rate increases independent of anxiety. The present investigation compared magnitude of heart rate changes observed under conditions of winning and losing money. Results showed: no differences between incentive and response cost conditions; no effect of state anxiety on heart rate in these conditions, despite an elevation of state anxiety on the task day relative to a subsequent relaxation day assessment; and some evidence for the presence under both such appetitive conditions of cardiovascular hyperresponsivity among offspring of hypertensive parents. The results suggest a need for systematic parametric studies of experimental conditions.

Cardiac responses to psychological tasks: impedance cardiographic studies

In a series of studies, cardiac activity, assessed with an impedance cardiograph, was monitored as college students performed either a visual search or pursuit rotor task. Heart rate, systolic time intervals, stroke volume, cardiac output and the Heather (1969) index of contractility were measured before, during and after performance. In the first study, visual search did not affect the participants' (N = 44) level of cardiac output or their length of the pre-ejection period. It is likely that the lack of charge in cardiac output resulted from a fall in stroke volume and in the Heather index while the task was performed. Heart rate was most rapid during performance and emerged as the only measure affected by the withdrawal of monetary incentives for failure to solve the visual search problem. In the second study, 40 subjects performed a pursuit rotor task and increases in cardiac output as well as changes in all of the other cardiac measures occurred. The level of task difficulty influenced the extent of heart rate increases and stroke volume decreases during performance. An additional 20 male subjects participated in a third study in which the level of difficulty of the pursuit rotor task was signalled and the order of the levels of difficulty was balanced across trial blocks. Under these conditions, the changes in cardiac activity before, during and after performance were similar to those observed in the first two studies. Heart rate was the only measure sensitive to the level of task difficulty. In general, the findings underscore the sensitivity of heart rate to changes in subtle aspects of psychological situations. To enlist increases in cardiac output and inotropic parameters extensive alterations in behavioral state are required.