Differentiating challenge reactivity from psychomotor activity in studies of children's psychophysiology: considerations for theory and measurement

Current methods of assessing children’s physiological “stress reactivity” may be confounded by psychomotor activity, biasing estimates of the relation between reactivity and health. We examined the joint and independent contributions of psychomotor activity and challenge reactivity during a protocol for 5- and 6-year-old children (N = 338). Measures of parasympathetic reactivity (respiratory sinus arrhythmia [RSA]) and sympathetic reactivity (preejection period [PEP]) were calculated for social, cognitive, sensory, and emotional challenge tasks. Reactivity was calculated relative to both resting and a paired comparison task that accounted for psychomotor activity effects during each challenge. Results indicated that comparison tasks themselves elicited RSA and PEP responses, and reactivity adjusted for psychomotor activity was incongruent with reactivity calculated using rest. Findings demonstrate the importance of accounting for confounding psychomotor activity effects on physiological reactivity.     

Autonomic reactivity during viewing of an unpleasant film.

The effect of an aversive, high-arousing film on heart rate, respiratory sinus arrhythmia, and electrogastrographic activity (EGG) was investigated. Previous studies have indicated a larger heart-rate deceleration for visual stimuli depicting surgery or blood compared to neutral content, and this phenomenon is similar to the bradycardia observed in animals in response to fear. The heart-rate deceleration is clearly parasympathetically driven, and it is considered a general index of attention. An accurate index of cardiac vagal tone can be obtained by means of quantification of the amplitude of respiratory sinus arrhythmia. The relationship between cardiac vagal tone and EGG is complex, but animal research has shown that suppressing vagal activity dampens gastric motility. We have investigated whether a movie depicting surgery is associated with greater heart-rate deceleration, larger increase in respiratory sinus arrhythmia, and greater increase in EGG activity compared to a neutral movie. In addition, if both respiratory sinus arrhythmia and EGG are indices of vagal tone, a positive correlation between these physiological responses was expected. Analysis indicated an effect of the surgery movie on heart rate and respiratory sinus arrhythmia, but not on EGG activity. Moreover, the expected correlation was not found. Implications for future studies are discussed.     

Heart rate and respiration in reptiles: contrasts between a sit-and-wait predator and an intensive forager

The current study investigated respiration and heart rate in two species of reptiles with distinct behavioral strategies: (1) the Sudan plated lizard (Gerrhosaurus major), a sit-and-wait predator; and (2) the Savanna monitor (Varanus exanthematicus), an intensive forager. It was hypothesized that (a) the plated lizard would not express respiratory sinus arrhythmia, and (b) the monitor, a reptile with behavioral and physiological characteristics similar to mammals, might express respiratory sinus arrhythmia, a pattern previously observed only in mammals. The data demonstrated that although there were strong vagal influences on the heart, respiratory activity was not manifested in the heart rate pattern of the plated lizards. In contrast, the monitor exhibited a reliable ventilatory influence on the heart rate pattern, although the pattern differed from the respiratory sinus arrhythmia observed in mammals. Consistent with the Polyvagal Theory (), the vagal control of the reptilian heart in both species appears to be mediated through the phylogenetically older unmyelinated system, a system that evolved to support metabolic conservation and not social behavior.     

Contributions of Psychophysiology to Media Research: Review and Recommendations

Despite the increasing use of psychophysiological measures in various research areas, there is a relative paucity of studies on communication, media, and media interfaces that have taken advantage of this approach. This article provides an overview of the use of psychophysiological measures of attention and emotion in media research with the focus on 3 most commonly used measures: heart rate, facial electromyography, and electrodermal activity. Selected media studies that have used psychophysiological methods to test theory-based predictions regarding the role of attentional and emotional factors in message processing are critically reviewed. The article also highlights some methodological and other issues critical for the successful application of psychophysiological methods to problems in media research. In particular, respiratory sinus arrhythmia (RSA), a selective index of parasympathetic nervous system activity, is introduced as a measure that holds particular promise for media research, given that RSA is highly sensitive to changes in attention.     

Getting to the heart of personality in early childhood: Cardiac electrophysiology and stability of temperament

Can detection of highly stable individual differences in temperament in early childhood be enhanced using measures of resting heart rate (HR) and respiratory sinus arrhythmia (RSA)? The current longitudinal study (N = 216, 50% female; two to four years old) tested the statistical moderating effects of longitudinal change in resting HR and RSA on stability of mother-rated temperament. Children with the smallest decreases in resting HR and smallest increases in resting RSA had the most stable individual differences in effortful control. In contrast, those with the largest increases in resting RSA had the most stable individual differences in surgency. Including information on HR and RSA can be useful, though the effects depend on the trait and physiological indicator in question.     

A preliminary study of the comfort of paced respiration

In order to obtain basal information about what type of externally paced respiration is comfortable, 25 male and 25 female undergraduate students were asked to practice self‐paced respiration. After a 1‐min rehearsal following instructions on comfortable self‐paced respiration, subjects carried out 2 min of self‐paced respiration and rated their level of comfort on a scale of 1–5. This was repeated (up to a maximum of seven times) until the subject recorded a high rating. Results indicated that self‐paced respiration was most comfortable, irrespective of sex, when a respiratory pattern was attained of half the respiratory rate and nearly twice the tidal volume of the trainee's resting condition. Although respiratory sinus arrhythmia and heart rate were indicative of a decrease in cardiac vagal activity and end‐tidal PCO₂ was suggestive of a reduction in anxiety, these effects were small. The results have implications for the utilization of externally paced respiration.     

Can the distress-signal and arousal-reduction views of crying be reconciled? Evidence from the cardiovascular system

Theorists have staked out two ostensibly opposing views of human crying as either an arousing behavior that signals distress or a soothing behavior that reduces arousal after distress. The present study examined whether these views of crying might be reconciled by attending to physiological changes that unfold over crying episodes. Sixty female students watched neutral and cry-eliciting films while autonomic physiology, including respiratory sinus arrhythmia and pre-ejection period, was assessed. Crying participants exhibited heart rate increases that rapidly subsided after crying onset. Crying onset was also associated with increases in respiratory sinus arrhythmia and slowed breathing. All crying effects subsided by 4 minutes after onset. It is possible that crying is both an arousing distress signal and a means to restore psychological and physiological balance, depending on how and when this complex behavior is interrogated.     

A MATLAB toolbox for correcting within-individual effects of respiration rate and tidal volume on respiratory sinus arrhythmia during variable breathing

Respiratory sinus arrhythmia (RSA) is a common estimator of vagal outflow to the heart, dependent on parasympathetic activity. During variable breathing, both respiration rate and tidal volume contribute substantially to within-individual RSA variance. A respiratory control method allows for within-individual correction of the time-domain index of RSA. rsaToolbox is a set of MATLAB programs for scoring respiration-corrected RSA using measurements of cardiac interbeat intervals, respiratory-cycle times, and tidal volumes, recorded at different paced-breathing frequencies. The within-individual regression of RSA divided by tidal volume upon total respiratory cycle time is then used to estimate the baseline vagal tone for each breath of a given total respiratory-cycle time. During a subsequent analysis, the difference between the observed RSA (divided by the tidal volume at each breath) and the RSA divided by the tidal volume that was predicted by the baseline equation serves as an estimate of changes in vagal tone. rsaToolbox includes a graphical user interface for intuitive handling. Modular implementation of the algorithm also allows for flexible integration within other analytic strategies or for batch processing.     

Resting respiratory sinus arrhythmia buffers against rejection sensitivity via emotion control

Emerging evidence suggests that high resting heart rate variability in the respiratory frequency band, or respiratory sinus arrhythmia (RSA) may capture individual differences in the capacity to engage in situationally appropriate regulation of affect and behavior. The authors therefore hypothesized that high RSA may act as a protective factor against difficulties controlling negative affect and hostile behaviors in conflicts with romantic partners in highly rejection-sensitive individuals--a population otherwise vulnerable to these responses. Results were consistent with this hypothesis such that highly rejection-sensitive participants reported less emotion control and more hostility in conflicts only if they were also low in RSA. Furthermore, emotion control mediated the joint effect of rejection-sensitivity and RSA on hostile conflict behavior. These results are consistent with the argument that resting RSA is a marker of flexible responding in the context of highly emotional situations, and further suggest that it may serve as a protective factor particularly in vulnerable populations.     

Individual differences in adolescents' sympathetic and parasympathetic functioning moderate associations between family environment and psychosocial adjustment

The present study tested whether individual differences in autonomic nervous system functioning interact with environmental risk factors to predict adolescents' psychosocial functioning. The authors assessed skin conductance and respiratory sinus arrhythmia at rest and during laboratory stressors in 110 14-year-olds. Subsequently, adolescents and their mothers provided both questionnaire and daily diary data (over 10 days) on emotional and interpersonal functioning. The authors found stronger associations between environmental risk factors (having a single-mother household or a mother with high internalizing problems) and psychosocial outcomes (externalizing problems, daily negative affect, and daily interaction quality) among youths with specific patterns of tonic and stress-induced sympathetic and parasympathetic nervous system activity, but the pattern of moderating effects differed between boys and girls. The findings support the notion that individual differences in autonomic functioning index variation in youth's susceptibility to environmental risk factors.     

Going beyond heart rate: autonomic space and cardiovascular assessment of mental workload

Psychophysiological assessment of pilot mental workload using heart rate should be augmented with an autonomic space model of cardiovascular function. This model proposes that autonomic nervous system influences on the heart may change with psychological processing in ways that are not evident in heart rate. A method of mental-workload assessment was proposed that used multiple psychophysiological measures of cardiovascular responsivity to derive the underlying sympathetic and parasympathetic information needed to represent the autonomic space for heart rate. Principal-components analysis was used to extract Sympathetic and Parasympathetic components from heart period, residual heart period. respiratory sinus arrhythmia, and Traube-Hering-Mayer wave in three experiments that manipulated perceptual/central processing and physical task demands. This initial evaluation of the method concluded that the autonomic components were valid and that the components had greater diagnosticity, and for some manipulations greater sensitivity, than heart rate. These results support the contention that the Sympathetic and Parasympathetic components provided increased precision for mental-workload assessment.     

Effects of suppression and acceptance on emotional responses of individuals with anxiety and mood disorders

The present investigation compared the subjective and physiological effects of emotional suppression and acceptance in a sample of individuals with anxiety and mood disorders. Sixty participants diagnosed with anxiety and mood disorders were randomly assigned to one of two groups. One group listened to a rationale for suppressing emotions, and the other group listened to a rationale for accepting emotions. Participants then watched an emotion-provoking film and applied the instructions. Subjective distress, heart rate, skin conductance level, and respiratory sinus arrhythmia were measured before, during, and after the film. Although both groups reported similar levels of subjective distress during the film, the acceptance group displayed less negative affect during the post-film recovery period. Furthermore, the suppression group showed increased heart rate and the acceptance group decreased heart rate in response to the film. There were no differences between the two groups in skin conductance or respiratory sinus arrhythmia. These findings are discussed in the context of the existing body of research on emotion regulation and current treatment approaches for anxiety and mood disorders.     

Heart rate deceleration after erroneous responses

Summary In an eight-choice reaction task, the influence of erroneous responses upon the temporary changes in the level of heart rate (HR) was studied. It was shown that after errors there was a short-term deceleration of the HR-level, while after correct responses an accelerating tendency was found. This phenomenon has to be regarded as an additional source of fluctuations of the HR-level. Therefore, it has to be taken into account when suppression of sinus arrhythmia is used for assessing the level of mental load.     

STAR: A unique embedded performance assessment technique

STAR (The Strategic and Tactical Assessment Record) is a versatile research tool designed to evaluate the effects of sustained performance and other stressors on integrated, complex cognitive functioning. This completely automated task is presented in the form of a highly motivating computer game. However, unlike typical computer games, successful performance of STAR depends on an individual’s ability to rapidly and accurately assess risk/benefit ratios in a variety of situations, and on the skilled use of an array of multipurpose control systems. STAR is unique in that approximately 80 performance measures are unobtrusively embedded in the operations required to “play the game”; no obvious performance assessment interferes with task presentation. STAR provides multiple measures of psychomotor function, attention, memory, information processing, decision making, risk-taking behavior, subjective state, errors, and error paths. In this report, we describe STAR, and summarize two preliminary experiments designed to separately evaluate the effects of task difficulty and task stress level on complex performance.     

The worried mind: autonomic and prefrontal activation during worrying

To study the psychophysiological correlates of worrying, the authors recorded heart rate, respiratory sinus arrhythmia (RSA), skin conductance level, and alpha electroencephalographic asymmetry in healthy males during baseline, relaxation, worry induction, and anticipation of an impromptu speech task. Compared with baseline, relaxation, and anticipation, worrying was associated with greater heart rate and lower RSA. Worrying was further characterized by higher skin conductance levels compared with baseline but lower levels than during anticipation. Finally, worrying was associated with relatively greater left frontal activity compared with anticipation. Trait public speaking anxiety was positively correlated with left frontal activity during worrying. These results support the notion that worrying is a unique emotional state that is different from fearful anticipation.     

Shy toddlers act bold: The roles of respiratory sinus arrhythmia and parent emotion language

Shy children show reticence in social contexts, presumably as a way of regulating their fear. The present study evaluated whether toddler physiological regulation and parent emotion language facilitated shy toddlers’ (21–24 months) engagement with an unfamiliar female examiner. Toddler high basal respiratory sinus arrhythmia was positively associated with bold approach with the examiner. Parent emotion explanations were positively associated with toddler bold approach, particularly for toddlers with low basal respiratory sinus arrhythmia. Findings suggest that toddlers’ dispositional capacity for regulation and parents’ explanations of emotion in everyday conversations with their toddlers may help shy toddlers to socially engage.     

Degree of extraversion and physiological responses to physical pain and sadness

Extraversion is a personality frequently discussed as one of the strongest and most consistent factors that relates to individual subjective wellbeing. The goal of this study was to better understand how people with varying degrees of extraversion psychologically and physiologically respond differently to unpleasant circumstances. Emotional responses (e.g., levels of intensity, valence, and arousal) were assessed in determining the sensitivity level to negative stimuli that were specifically designed to provoke physical pain and sadness emotion. Physiological changes (e.g., heart rate (HR), blood volume pulse (BVP), and respiratory sinus arrhythmia (RSA)) were also measured during pain and sadness to observe sympathetic and parasympathetic activities. Our results showed that the degree of extraversion was associated with less unpleasant responses to sadness, less HR responses to both pain and sadness, and greater RSA responses to sadness. The findings suggest that the lower HR reactivity to painful and sad situations and greater RSA reactivity to sad situations in extraversion could be possibly due to increased parasympathetic activity. Additionally, enhanced parasympathetic activity to negative situations may explain an important mechanism underlying the positive connection between extraversion and subjective wellbeing.     

Operant conditioning of the EEG in two patients with epilepsy: Methodologic and clinical considerations

Methodologic and clinical considerations are discussed in sensorimotor rhythm (SMR) biofeedback research on two dissimilar but severe epileptic males. The first case, an akinetic epileptic who prior to feedback training experienced 80–100 clinical seizures every 10 hours, showed considerable seizure reduction after 6 months of SMR and epileptiform training. A number of methodologic and instrumentation advances were pioneered with the akinetic patient: (1) development of and ultra-sharp band-pass filter; (2) use of epileptiform inhibit and feed-back circuitry; (3) use of monetary rewards as additional incentive; (4) use of correlational analysis for evaluation of acquisition in the major dependent variables and; (5) use of noncontingent feedback and rein-forcement as control techniques. The second case, a psychomotor epileptic, also showed therapeutic benefit from SMR training. Clinical information regarding the effect of anticonvulsant medications on the course and therapeutic outcome of SMR training are described. In conjunction with operant conditioning of 12 Hz activity, corresponding changes for other EEG parameters are examined.     

A mechanical method for changing heart rate and blood pressure

The investigation of afferent cardiovascular influences upon central nervous processes needs a methodology which allows for independent and systematic manipulation of circulatory processes. By mechanical manipulation of posture (tilt table, orthostasis) and compression of lower body parts (by anti-G-suit) reliable changes in heart rate and blood pressure can be induced. In fourty subjects (study 1) it could be shown that sustained (30 min.) changes in heart rate (e.g. orthostatic tachycardia, decrease of heart rate during compression) and mean arterial blood pressure (increase during orthostasis with and without compression) occur. Although changes in heart rate could be achieved irregardless of whether the venous "pooling" was suppressed by an air- or water-filled pressure suit, the pressor effect did differ quite considerably. In fourty-four subjects (study 2) it could be demonstrated that only by means of an water-filled suit further increases in mean arterial blood pressure could be evoked during orthostasis. Changes in hemodynamic also lead to changes in sympatho-vagal control of cardiac activity. In study 3 (ten subjects) it could be shown, that orthostasis mainly evokes alterations in sympathetic activity whereas lower body compression leads to additional increases of vagal activity and respiratory sinus arrhythmia during orthostasis.     

Effects of instructions and biofeedback on EEG-alpha production and the effects of EEG-alpha biofeedback training for controlling arousal in a subsequent stressful situation

In Phase One, 44 subjects participated in a 2 (instructions to increase alpha, no instructions to increase alpha) × 2 (alpha biofeedback, no alpha biofeedback) factorial experiment. Results indicated that increases in alpha production were due to instructions to increase alpha and that biofeedback had no effect on alpha production. In Phase Two, the 44 subjects from Phase One were exposed to a threat of shock whereas 11 additional subjects in a control condition were not. The design employed in Phase Two was a 2 (previous instructions and stress, no previous instructions and stress) × 2 (previous biofeedback and stress, no previous biofeedback and stress) plus 1 (no previous instructions/no previous biofeedback, no stress). Results indicated that the threat of shock was effective in increasing arousal (as measured by heart rate and skin resistance) but previous EEG-alpha biofeedback training was not effective in helping subjects decrease arousal while in the stressful situation. The results indicate that it is the instructions (and related information concerning alpha) rather than the biofeedback that is critical in alpha biofeedback training and that this training does not appear to have utility for controlling arousal under stress.