Cardiac and metabolic responses to "space invaders": an instance of metabolically-exaggerated cardiac adjustment?

Effects of Cybersickness Caused by Head-Mounted Display-Based Virtual Reality on Physiological Responses: Cross-sectional Study

Background

Although more people are experiencing cybersickness due to the popularization of virtual reality (VR), no official standard for the cause and reduction of cybersickness exists to date. One of the main reasons is that an objective method to assess cybersickness has not been established. To resolve this, research on evaluating cybersickness with physiological responses that can be measured in real time is required. Since research on deriving physiological responses that can assess cybersickness is at an early stage, further studies examining various physiological responses are needed.

Objective

This study analyzed the effects of cybersickness caused by head-mounted display–based VR on physiological responses.

Methods

We developed content that provided users with a first-person view of an aircraft that moved (with translation and combined rotation) over a city via a predetermined trajectory. In the experiment, cybersickness and the physiological responses of participants were measured. Cybersickness was assessed by the Simulator Sickness Questionnaire (SSQ). The measured physiological responses were heart rate, blood pressure, body temperature, and cortisol level.

Results

Our measurement confirmed that all SSQ scores increased significantly (all Ps<.05) when participants experienced cybersickness. Heart rate and cortisol level increased significantly (P=.01 and P=.001, respectively). Body temperature also increased, but there was no statistically significant difference (P=.02). Systolic blood pressure and diastolic blood pressure decreased significantly (P=.001).

Conclusions

Based on the results of our analysis, the following conclusions were drawn: (1) cybersickness causes significant disorientation, and research on this topic should focus on factors that affect disorientation; and (2) the physiological responses that are suitable for measuring cybersickness are heart rate and cortisol level.

The Candy Crush Sweet Tooth: How 'Near-misses' in Candy Crush Increase Frustration, and the Urge to Continue Gameplay

Like many gambling games, the exceedingly popular and lucrative smartphone game "Candy Crush" features near-miss outcomes. In slot machines, a near-miss involves getting two of the needed three high-paying symbols on the pay-line (i.e., just missing the big win). In Candy Crush, the game signals when you just miss getting to the next level by one or two moves. Because near-misses in gambling games have consistently been shown to invigorate play despite being frustrating outcomes, the goal of the present study was to examine whether such near-misses trigger increases in player arousal, frustration and urge to continue play in Candy Crush. Sixty avid Candy Crush players were recruited to play the game for 30 min while having their Heart Rate, Skin Conductance Level, subjective arousal, frustration and urge to play recorded for three types of outcomes: wins (where they level up), losses (where they don't come close to levelling up), and near-misses (where they just miss levelling up). Near-misses were more arousing than losses as indexed by increased heart rate and greater subjective arousal. Near-misses were also subjectively rated as the most frustrating of all outcomes. Most importantly, of any type of outcome, near-misses triggered the most substantial urge to continue play. These findings suggest that near-misses in Candy Crush play a role in player commitment to the game, and may contribute to players playing longer than intended.

Automatic control of negative emotions: evidence that structured practice increases the efficiency of emotion regulation

Emotion regulation (ER) is vital to everyday functioning. However, the effortful nature of many forms of ER may lead to regulation being inefficient and potentially ineffective. The present research examined whether structured practice could increase the efficiency of ER. During three training sessions, comprising a total of 150 training trials, participants were presented with negatively valenced images and asked either to “attend” (control condition) or “reappraise” (ER condition). A further group of participants did not participate in training but only completed follow-up measures. Practice increased the efficiency of ER as indexed by decreased time required to regulate emotions and increased heart rate variability (HRV). Furthermore, participants in the ER condition spontaneously regulated their negative emotions two weeks later and reported being more habitual in their use of ER. These findings indicate that structured practice can facilitate the automatic control of negative emotions and that these effects persist beyond training.

Validity and Reliability of a Classroom Heart-Rate Collection Procedure, with Application for Assessing Arousal Related to Test Anticipation

Measures of cardiac reactivity can be very effective classroom tools for conducting educational activities in psychology courses. Sophisticated laboratory methods provide valid and reliable data, but are costly and have poor ecological validity. In this article, Study 1 established the validity and reliability of a simple method for obtaining self-measures of heart rate in the classroom. The author assessed validity by obtaining self-measures of pulse repeatedly from 74 students, and then correlating them to the students' heart rates measured by electrocardiography in the lab. He also assessed test-retest reliability and internal consistency of self-measures of heart rate. Study 2 utilised the procedure described in Study 1 to assess cardiac reactivity of a group of 107 students prior to taking a test. Mean heart rates were significantly elevated in the test situation. Gender differences were also significant. The findings reported in this article illustrate that self-measured pulse rate taken by students simultaneously in class is a reliable and valid way of assessing cardiac reactivity in educational settings.

Usefulness of laboratory mental stress test in patients with stable coronary artery disease

BACKGROUND AND HYPOTHESIS

Many episodes of ischemia in daily life are silent occurring during sedentary activities and may be related to mental stress. In 35 patients with stable angina and positive exercise test awaiting bypass surgery, we investigated whether laboratory mental stress tests would trigger ischemia of a comparable severity to that occurring in daily life and attempted to elucidate some of the underlying mechanisms.

METHODS

All patients underwent exercise testing, personality assessment, 2-day Holter monitoring, and laboratory mental stress tests while on their usual medications.

RESULTS

Only four patients (12%) had positive mental stress test (ST depression > or = 0.1 mV). All episodes were silent and usually associated with fast heart rate (> 90 beats/min). In contrast, ambulatory ischemia was common (average duration of 51 min per 24 h), and at least one episode was recorded in 27 patients (77%) including the 4 with positive test. Patients with positive mental stress test had a higher heart rate during testing (124 +/- 24 vs. 86 +/- 16 beats/min, p < 0.01), and a shorter exercise time and time to 1 mm ST depression on cycle ergometry than those with negative mental stress test. None of the four patients were on beta blockers. There was no difference in personality inventory between the two groups. Comparisons between patients with and without positive mental stress test revealed no difference in the duration and frequency of ambulatory ischemia, or in the occurrence of silent ischemia. However, the heart rate at onset of ambulatory ischemia tended to be higher in the patients with positive mental stress test (96 +/- 9 vs. 62 +/- 43, p = 0.07). Further subgroup analysis in patients without beta blockers (4 mental stress test positive and 18 negative) showed similar results.

CONCLUSIONS

Laboratory mental stress test is a weak inducer of ischemia detected by electrocardiographic monitoring in patients with frequent ambulatory ischemia. Wall motion evaluation during mental stress test may improve sensitivity. While larger scale studies may determine its clinical role, the present study illustrated that patients with heightened heart rate response to mental stress were identified in whom beta blockers could be the drug of choice.

Cognitive demand and blood glucose

Previous research has identified that glucose administration can enhance cognitive performance, especially during more intense cognitive processing. There appears to be a reciprocal relationship between falling glucose levels and cognitive performance, particularly under conditions of cognitive demand. The present placebo-controlled, double-blind, balanced, crossover study examined the possibility that a high cognitive load may produce changes in blood glucose levels. A secondary aim was to examine the effects of glucose on tasks of varying cognitive demand load. The effects of a glucose drink on participants' performance of a serial subtraction task (computerised Serial Sevens), a somatically matched control task (key-pressing), a short interval Word Memory task and a Word Retrieval (Verbal Fluency) task were assessed. The change in blood glucose during the demanding computerised Serial Sevens was compared to the change occurring during the key-pressing control. Glucose consumption significantly improved performance on Serial Sevens, with a trend for improved performance on Word Retrieval and no effect on the Word Memory task. Compared with the control task, Serial Sevens resulted in a significant reduction in blood glucose in both drink conditions. This accelerated decay was significantly greater following glucose than placebo. It is suggested that the amount of cognitive load associated with task performance is an index of its sensitivity to enhancement by glucose. Furthermore, a period of intense cognitive processing leads to a measurable decrease in levels of peripherally measured blood glucose, which may be linked to increased neural energy expenditure. However, the relative contribution of central and peripheral (e.g. cardiac) activity to this effect has yet to be determined.

The effect of attentional load on the breathing pattern in children

Experiments designed to establish the effects of video games on breathing patterns have led to contradictory results. Several authors reported that video games tended to increase breathing frequency (i.e. to reduce breath duration), whereas others reported the opposite. We postulated that video games contain different psychophysiological components which may have opposite effects on breathing pattern. On the one hand, arousal and emotion may tend to stimulate breathing. On the other, focusing attention on the game may prompt subject to inhibit any movement--including breathing--which might be a potential nuisance variable. The aim of this study was to assess the specific effects of the attentional load in an experimental environment characterized by its low emotional impact. We measured breathing variables, cardiac frequency and cortisol levels in 10 healthy children (mean age = 9.2 +/- 1.5 years) who were familiar with the environment, the experimenter and the video game. Breath duration rose significantly, from 2.56 to 3.16 s, as a function of game difficulty. Cortisol levels, heart rate and the thoracic contribution to breathing displayed no significant changes. Taken together, these data suggest that focusing attention on the game tended to inhibit breathing and that previous contradictory reports in this respect were due to the confounding effects of emotion.

Psychophysiological aspects of selective and divided attention during continuous manual tracking

Central, autonomic, and metabolic physiological measures were observed concurrently along with performance and subjective measures to compare the effects of tracking task difficulty during selective and divided attention. Eighteen dextral males performed visual compensatory manual tracking as a primary task while attending to or ignoring secondary-task auditory oddball stimuli. The difficulty of the tracking task was varied factorially by requiring participants to track with acceleration (second-order) or velocity (first-order) control and high or low bandwidth sum-of-sines disturbance. Tracking performance was affected by the difficulty manipulations but not by the attention manipulation. Event-related brain potential P300 amplitude to oddball target stimuli was sensitive to the division of attention and tracking order-of-control but not to tracking disturbance bandwidth when the oddball task was attended. Oxygen consumption, a measure of aerobic metabolism, was greater during acceleration than velocity tracking; however, cardiac measures were sensitive only to the division of attention. The results demonstrate that the attention and the task difficulty manipulations have physiologically dissociable effects that were interpreted as supporting a cognitive/energetic model of attention.

Hemodynamic responses during psychological stress: Implications for studying disease processes

Investigation of the physiological correlates of psychological stress is of interest in relation to the putative impact of stress in the etiology of cardiovascular disease. Although the assessment of blood pressure and heart rate responses to psychological stress has been very informative, the addition of cardiac output measurement has added a further dimension to this research field. In recent studies, a more complete hemodynamic picture of the stress response has been documented in terms of cardiac output and systemic vascular resistance components of blood pressure changes. Different stressors have been shown to produce similar blood pressure increases due to quite different hemodynamic mechanisms. Furthermore, when faced with the same stressor, different individuals may exhibit pressor responses that are very different hemodynamically. There is growing evidence that these hemodynamic response patterns to psychological stress are stable individual traits. Response stability is a prerequisite for considering how stress-related hemodynamic changes may be implicated in the pathophysiology of cardiovascular diseases. Observations that hemodynamic response patterns in individuals at higher risk for the development of hypertension differ from those of lower risk individuals show that specific patterns of hemodynamic response are associated with disease processes. Although it is as yet unclear whether they represent markers or mechanisms. Overall. hemodynamic studies appear to he helping to refine our understanding of how stress can impact cardiovascular disease processes.

Emotions and respiratory patterns: review and critical analysis

The literature on emotions and respiration is reviewed. After the early years of experimental psychology, attention to their relationship has been sparse, presumably due to difficulties in adequate measurement of respiration. The available data suggest nevertheless that respiration patterns reflect the general dimensions of emotional response that are linked to response requirements of the emotional situations. It is suggested that the major dimensions are those of calm-excitement, relaxation-tenseness, and active versus passive coping. Research on the emotion-respiration relationships has been largely restricted to the correlates of respiration rate, amplitude, and volume. Finer distinctions than those indicated may well be possible if a wider range of parameters, such as the form of the respiratory cycle, is included in the investigation.

Metabolic and cardiorespiratory measures of mental effort: the effects of level of difficulty in a working memory task

24 participants (12 female) performed a continuous memory task during which metabolic, cardiorespiratory, performance, and subjective mental workload measures were taken. Task difficulty was varied using two manipulations in a within-subjects factorial design: memory load (one or three items) and temporal demand (interstimulus intervals of 2, 3, or 4 s). Males and females differed in initial metabolic rate, but did not differ in their response to the task. Memory load affected all measures, while temporal demand affected only respiration rate, performance, and subjective mental workload. Metabolic, Respiratory, Cardiovascular, and Subjective/Performance components were identified in a principal components analysis (PCA), and the Respiratory and Subjective/Performance components were affected by the task manipulations. When performance quality was examined, the Metabolic component revealed that poor performers had greater energy expenditure during the task than good performers, and the Cardiovascular component revealed that good and poor performers differed in their response to memory load and temporal demand. Cardiac and metabolic changes during mental work were not a function of overall mental effort, but were specific to the effort due to memory load and to the individual differences among participants in their ability to perform the task. However, respiration was sensitive to the mental effort associated with both memory load and temporal demand, but was not sensitive to individual differences.

Component analysis of task-related respiratory patterns

The pattern of breathing, determined by time, volumetric and respiratory shape parameters was examined in male students subjected to mental arithmetic tasks, sustained attention tasks, a relaxation task and four levels of graded exercise. Also, the relationships among the respiratory time parameters were determined by performing a factor analysis on a pooled matrix containing the parameter correlations across all experimental conditions. Relative to baseline, the experimental tasks induced rather distinct breathing patterns. During exercise the breathing curves resembled a triangular shape which was caused by a decrease in total breath duration coupled to an increase in both the depth of breathing and the inspiratory duty cycle time. For both the sustained attention and mental arithmetic conditions there was a slight decrease in the depth of breathing and a more pronounced decrease in inspiration time. However, during mental arithmetic the decrease in inspiration was linked to an increase in expiration duration, exhibiting a breathing curve that resembled a 'saw tooth'. In contrast, the attention tasks induced a slight decrease in expiration duration showing a sinusoidal breathing curve which was more similar to the baseline and relaxation breathing pattern. The factor analysis revealed two respiratory factors: a time factor reflecting inspiration, expiration and total cycle duration and a factor related to the inspiratory duty cycle time. We conclude that analysis of breathing patterns with components other than rate and depth of breathing is a potentially useful research tool.

Respiration in psychophysiology: methods and applications

With the use of advanced equipment, respiratory measures can unobtrusively and reliably be assessed in a variety of psychophysiological research settings. New computerized analysis techniques can break down respiration into a number of components that provide valid estimates of variations in respiratory control mechanisms in the brain stem. Thus analysed, respiratory responses may vary in at least two dimensions: (A) with regard to drive and timing aspects, and (B) with regard to the metabolic appropriateness of the respiratory response. Assessment of respiratory responses may be relevant for a broad variety of research areas, including studies of the physiological effects of mental load and stress, investigations of physiological correlates of emotions and affect, and research linking physiological responses to subjective distress and psychosomatic disorders.

Psychophysiological theories on sympathetic nervous system reactivity in the development of essential hypertension

Psychophysiological theories on the development of essential hypertension are reviewed and evaluated. Two interconnected theories that relate behavior to essential hypertension and account for individual differences in susceptibility to disease are the "hyperreactivity" theory and "the symptom specificity" theory. The "hyperreactivity" theory identifies individual differences in autonomic nervous system reactivity as the pathophysiological mechanism and the "symptom specificity" theory suggests that inflexible, stereotypical responding increases the risk to develop hypertension. Based on a literature review, these theories are examined. There exist both case/control and prospective studies on autonomic nervous system reactivity and the development of hypertension. It is concluded that a neurogenically mediated hyperreactivity to stress is a precursor and not an effect of hypertension. Tasks that call for active but not passive coping efforts are more efficient elicitors of reactivity differences between those at high and low risk to develop hypertension in case/control studies. In prospective studies, active tasks may also have a predictive advantage over passive with respect to blood pressure development. In the early phase of hypertension, an increased cardiovascular reactivity is accompanied by increased neuroendocrine activation. In the later phase, heightened reactivity is confined to the cardiovascular system. This does not prove but is consistent with the notion that transient episodes of increased cardiac output translate into essential hypertension by causing vascular hypertrophy. Case/control studies suggest that an increased "symptom specificity", with stereotypical responding across multiple stressors, is independent of cardiovascular reactivity and a precursor of hypertension. The literature lacks prospective studies on the clinical relevance of stereotypical responding. It is suggested that the presence of both hyperreactivity and symptom specificity in a single individual increases the risk to develop essential hypertension.

Haemodynamic adjustments to mental stress in normotensives and subjects with mildly elevated blood pressure

Cardiac output, heart rate, stroke volume, pre-ejection period, total peripheral resistance, systolic and diastolic blood pressure, and oxygen consumption were monitored or derived in young men with mildly elevated casual blood pressures and unambiguously normotensive control subjects before, during, and after exposure to a mental arithmetic stress. Measurements were also taken while subjects underwent graded dynamic exercise. This permitted cardiac output-oxygen consumption regression equations to be calculated and, as a consequence, cardiac output during mental stress to be represented as additional cardiac output. Systolic and diastolic blood pressure were higher during all phases of the study in the mildly elevated blood pressure group. An overall groups effect during the mental stress phase of the experiment was observed for cardiac output and pre-ejection period, and the effect for stroke volume was close to significance. Significant Groups X Periods interactions were found for cardiac output and additional cardiac output, and the heart rate effect was nearly significant. Post-hoc comparisons here indicated that, in the main, group differences in these cardiac variables were more evident during the mental arithmetic stress than during the pre- and post-task baseline periods. Total peripheral resistance did not differ reliably between groups and the cardiac effects were specific to the mental stress phase of the study.

A twin study approach towards understanding genetic contributions to body size and metabolic rate

The genetic and environmental determinants of a brief assessment of metabolic rate at rest and under psychological stress were studied in 40 pairs of monozygotic and 40 pairs of dizygotic young adult male twins. Height, weight and age were employed as covariates. Univariate analyses showed a high heritability for height and weight and moderate heritability for metabolic rate. Classical twin analyses and multivariate genetic modeling indicated that genetic influences on resting metabolic rate were entirely explained by body weight: there was no independent genetic contribution to resting metabolic rate. Metabolic rate under psychological stress, on the other hand, showed a significant genetic effect. The exponent (3/4) in the power function relating body weight to resting metabolic rate was the same as that found in a wide variety of animal species, a value that has been proposed as defining a body weight set point. We speculate that an adult body weight set point is genetically transmitted. Independent genetic effects on resting metabolic rate would be observed only when the normal equilibrium between body weight and metabolic rate is unbalanced during development, aging or disease. The study illustrates the use of multivariate genetic analyses of twin data which may be readily applied to widely used metabolic rate assessments.

Exaggerated sympathetic nervous system response to extended psychological stress in offspring of hypertensives

The cardiovascular responses of 24 healthy young adult males with a parental history of hypertension and 24 males without a parental history of hypertension to an extended active-coping psychological stressor were compared under three drug conditions: placebo, the beta 1-blocking agent metoprolol, and the alpha 1-blocking agent prazosin. In the placebo condition, offspring of hypertensives exhibited significantly greater heart rate, blood volume pulse, and forearm blood flow responses to the task. They also exhibited a significantly greater initial decrease in forearm vascular resistance, which, in contrast to the offspring of normotensives, was no longer significantly different from baseline levels by the end of the session. No group differences in blood pressure response were observed. Metoprolol eliminated the differences in heart rate and forearm vascular resistance responses. Prazosin eliminated the difference in blood volume pulse response and elicited a sustained group difference in forearm vascular resistance. These results implicate the sympathetic nervous system in the exaggerated cardiovascular responsivity to psychological stress in individuals with a family history of essential hypertension. They also suggest that the pattern of increasing vascular resistance in response to this stressor observed in this and other studies in this laboratory reflects alpha-adrenergic activity and not neurohumorally independent autoregulation.

Cardiovascular Reactivity Evoked by Means of Psychological and Physical Stressors

Cardiovascular effects of several physical and psychological stressors were investigated. Indirect continuous blood pressure as well as heart-rate were recorded. Systolic, diastolic, and mean blood pressure as well as heart-rate were recorded. Different patterns of cardiovascular activation during different stressors were obtained. The Valsalva manoeuvre evoked a basic negative feedback baro-receptor response. Physical exercise (bicycle ergometer stress) evoked an overriding of the baro-reflex sympathetic stimulation to fulfil metabolic needs. Psychological stressors such as a TV-game (‘space invaders’), a binary choice program and mental arithmetic produced a pattern of autonomic nervous stimulation which can be described as extra-metabolic or psychophysiological. Possible differences in reaction patterns between psychological stressors are discussed in the light of a literature study. ‘Active’ and ‘passive’ coping may be of importance.

Cardiovascular and metabolic activity at rest and during psychological and physical challenge in normotensives and subjects with mildly elevated blood pressure

Heart rate, systolic and diastolic blood pressure, and respiratory and metabolic activity were recorded prior to and during mental arithmetic and a video game task in 20 young men with mildly elevated casual systolic blood pressures. Twenty-five unambiguously normotensive young men were tested under the same protocol. For pretask baseline physiological activity, group differences emerged for all cardiovascular and metabolic variables; thus the elevated blood pressure group displayed not only higher resting cardiovascular levels than normotensive subjects, but higher levels of metabolic activity too. With regard to change in physiological activity from rest to task, the group with mildly elevated blood pressure showed reliably larger increases in heart rate to the mental arithmetic task than the normotensive subjects. These effects, however, were not paralleled by group differences in metabolic activity increase. Physiological measures were also taken prior to and during graded dynamic exercise. The subsequent calculation of individual heart rate-oxygen consumption exercise regression lines allowed the comparison of actual and predicted heart rates during psychological challenge. The subjects with mildly elevated blood pressure displayed significantly greater discrepancies between actual and predicted heart rate values than normotensives during the psychological tasks in general and mental arithmetic in particular. Group differences in physiological activity during exercise largely reflected the pattern seen at rest. A possible exception here was systolic blood pressure. Not only were systolic blood pressure levels higher throughout the exercise phase for mildly elevated blood pressure subjects, but this group evidenced more of an increase from rest to exercise than the normotensives.

Individual differences in heart rate response during behavioral challenge

This program of experiments examined heart rate responses to mental arithmetic and a video game. Attention first focused on their metabolic relevance. Comparison with heart rate/oxygen consumption regression equations generated from isotonic exercise data revealed that the heart rate increases of certain individuals were considerably in excess of those necessitated by contemporary metabolic demand. Both temporal and intertask consistency of reaction were explored, and supportive evidence was obtained. The relationship between laboratory and real-world reactions was investigated, and preliminary evidence found suggesting that in-laboratory responses are indicative of responses to more naturalistic stressors. Finally, twin studies examining the genetic and environmental determinants of individual differences in heart rate change during the tasks revealed a substantial genetic component for these responses.

Individual differences in heart rate and peripheral vascular responses to an extended aversive task

Psychophysiological research on situations requiring active coping has to this point dealt primarily with cardiac responses. Recent studies of vascular responses to such stressors have found conditions in high cardiac reactors that are possible precursors to autoregulatory vasoconstriction. The present study exposed 32 healthy male undergraduates to a one-hour shock avoidance procedure, with avoidance made contingent on video-game performance. Subjects also participated in a separate counterbalanced baseline session. The relationships among individual differences in heart rate, forearm blood flow, forearm vascular resistance, and digital blood volume pulse responses at different points in the stress session were examined. Decreases in forearm vascular resistance were observed only among high and medium heart rate reactors. As the session progressed, however, forearm vascular resistance responses of the medium heart rate reactors were sustained whereas those of the high heart rate reactors habituated despite the fact that heart rate and forearm blood flow responses remained elevated. The potential implications of this pattern of results to an autoregulation theory of hypertension development are discussed. Heart rate reactivity was inversely related to performance on the video-game task but was unrelated to Type A or anxiety.

Motor preparation aspects of cardiovascular reactivity to psychological challenge

Neural control of the circulation has evolved in such a way that behavioral responses to psychological stress may be accompanied by a dramatic activation of the cardiovascular system. This study was designed to address the hypothesis that such instances of cardiovascular mobilization reflect a functional motor preparation response. Twenty-four healthy young men participated in reaction time (RT) tasks which involved responding by squeezing a handgrip dynamometer. Motor preparation demands were manipulated by varying the temporal predictability of response requirements as well as the physical effort involved in responding, while controlling for other factors previously established to influence cardiovascular reactivity to psychologically challenging tasks. Physiological response measurements included heart rate, blood pressure and oxygen consumption. Increases in heart rate and systolic blood pressure during the RT tasks showed a general pattern which was consistent with the predictions of the motor preparation hypothesis, with the greatest elevations occurring in association with low temporal predictability and high physical effort. The possibility is discussed that factors such as incentives and elements of uncertainty may influence cardiovascular reactivity by accentuating behavioral arousal, of which motor preparation may be an inextricable component.

The effects of level of difficulty of mental arithmetic challenge on heart rate and oxygen consumption

Heart rate plus various metabolic and ventilatory indices were monitored while 18 young males engaged in a mental arithmetic task, structured to include 3 levels of difficulty; easy, difficult and impossible. Measurements were also taken while subjects undertook graded isotonic exercise on a bicycle ergometer; for each subject heart rate was plotted against oxygen consumption over the various exercise loads. Knowing oxygen consumption during the psychological tasks, these regression equations permitted the calculation of expected heart rates during each task condition and thus the computation of 'additional heart rate' as the difference between actual and predicted heart rate values. Additional heart rate was sensitive to variations in difficulty level; the difficult condition elicited reliably more additional heart rate than the easy and impossible conditions. Subjects' performance as well as their perceptions closely reflected the a priori classification of difficulty. Although subjects rated the easy condition as particularly unengaging, the impossible condition attracted relatively high rates of task involvement. It was argued that self-reports of this sort are probably more susceptible than cardiac activity to social demand characteristics.

Cardiac and somatic activation in the continuous perceptual-motor task: the significance of threat and serious-mindedness

The significance of serious-mindedness and task-contingent threat for cardiac and somatic activation were tested in a mixed design. Ten serious-minded and 10 playful state-dominant subjects were recruited from a larger sample to form extreme-groups according to their responses to the Telic Dominance Scale. They all performed a continuous perceptual-motor task with and without threat of aversive electric shock as punishment for inferior performance (counterbalanced). Results supported the following conclusions: serious-mindedness was associated with passive forearm EMG activity, whereas playfulness was related to active forearm EMG activity. Threat of shock interacted with serious-mindedness to cause particularily high HR with threat versus low HR in the no-threat treatment. Error-scores and scores on perceived task difficulty did not explain group differences in physiological activation. The results were discussed in relation to a hypothesis of cardiac-somatic uncoupling during effortful active coping, the pyramidal and extrapyramidal pathways to the skeletal muscles, and to effort expended in the serious-minded and playful motivational states.

A twin study of cardiac reactivity and its relationship to parental blood pressure

The cardiac reactivity of 40 monozygotic and 40 dizygotic pairs of young male twins was monitored during psychological challenge, as afforded by a video game. The observed pattern of variation could not be accounted for solely by environmental factors. In fact, a simple genetic model that implicated additive genetic effects, along with those stemming from individual environments, best fitted the data. In addition, cardiac reactions were substantially greater for subjects whose parents both had relatively elevated blood pressure. Overall, these data suggest individual differences in cardiac reactivity have a heritable component, and that high reactivity may be a precursor of elevated blood pressure.

Temporal consistency of individual differences in cardiac response to a video game

Three experiments are reported which examined the temporal stability of cardiac reactions to a video game of the 'space invaders' genre. Experiment 1 also addressed the matter of inter-task consistency; in addition to the video game, subjects were presented with an unsignalled reaction time task and led to believe that relatively quick reactions attracted financial reward, while slower ones brought either a burst of loud noise or withdrawal of money previously earned. Forty-two male subjects were tested on both tasks on two occasions, a week apart. Of the two tasks, the video game elicited the greater reactivity. In addition, individual variations in reactivity showed striking temporal stability for both tasks. However, inter-task consistency was much less marked; in fact, a significant inter-task correlation was obtained only on the first occasion of testing. It is probable that limited consistency here was in some measure due to the ineffectiveness of our reaction time task in eliciting substantial reactivity. Finally, reactivity was independent of baseline heart rate level. In experiment 2, three extreme high and three extreme low cardiac reactors were selected from an initial sample of 23 male subjects, on the basis of reactivity during an initial session with the video game, and subsequently studied during four further sessions. Once more, impressive stability of heart rate reactivity was apparent over sessions. In experiment 3, we examined the reliability of individual variations in cardiac reactivity in women and the issue of whether temporal stability is constrained by menstrual cycle effects. Twenty-four females were tested on the video game both preovulatory and postovulatory, with half being tested first during the preovulatory phase and half being tested first during the postovulatory phase. Again, the most striking finding was the marked stability of individual variations in cardiac reactivity over both time and menstrual cycle phase.