Pre-ejection Period Reactivity Research Articles

Effects of hearing acuity on psychophysiological responses to effortful speech perception

In recent studies, psychophysiological measures have been used as markers of listening effort, but there is limited research on the effect of hearing loss on such measures. The aim of the current study was to investigate the effect of hearing acuity on physiological responses and subjective measures acquired during different levels of listening demand, and to investigate the relationship between these measures. A total of 125 participants (37 males and 88 females, age range 37–72 years, pure-tone average hearing thresholds at the best ear between -5.0 to 68.8 dB HL and asymmetry between ears between 0.0 and 87.5 dB) completed a listening task. A speech reception threshold (SRT) test was used with target sentences spoken by a female voice masked by male speech. Listening demand was manipulated using three levels of intelligibility: 20 % correct speech recognition, 50 %, and 80 % (IL20 %/IL50 %/IL80 %, respectively). During the task, peak pupil dilation (PPD), heart rate (HR), pre-ejection period (PEP), respiratory sinus arrhythmia (RSA), and skin conductance level (SCL) were measured. For each condition, subjective ratings of effort, performance, difficulty, and tendency to give up were also collected. Linear mixed effects models tested the effect of intelligibility level, hearing acuity, hearing asymmetry, and tinnitus complaints on the physiological reactivity (compared to baseline) and subjective measures. PPD and PEP reactivity showed a non-monotonic relationship with intelligibility level, but no such effects were found for HR, RSA, or SCL reactivity. Participants with worse hearing acuity had lower PPD at all intelligibility levels and showed lower PEP baseline levels. Additionally, PPD and SCL reactivity were lower for participants who reported suffering from tinnitus complaints. For IL80 %, but not IL50 % or IL20 %, participants with worse hearing acuity rated their listening effort to be relatively high compared to participants with better hearing. The reactivity of the different physiological measures were not or only weakly correlated with each other. Together, the results suggest that hearing acuity may be associated with altered sympathetic nervous system (re)activity. Research using psychophysiological measures as markers of listening effort to study the effect of hearing acuity on such measures are best served by the use of the PPD and PEP.

Cognitive conflict does not always mean high effort: Task difficulty's moderating effect on cardiac response.

This article presents an experiment (N = 127 university students) testing whether the previously found impact of conflict primes on effort-related cardiac response is moderated by objective task difficulty. Recently, it has been shown that primed cognitive conflict increases cardiac pre-ejection period (PEP) reactivity-an index of effort intensity-during the performance of relatively easy tasks. This effect could be attributed to conflict-related negative affect. Consequently, as it has been shown for other types of negative affect, we expected conflict primes' effect to be task-context dependent and thus to be moderated by objective task difficulty. In a between-persons design, we manipulated conflict via embedded pictures of conflict-related vs. non-conflict-related Stroop items in a memory task. We expected primed conflict to increase effort in a relatively easy version of the task but to lead to disengagement when task difficulty was objectively high. PEP reactivity corroborated our predictions. Rather than always increasing effort, cognitive conflict's effect on resource mobilization was context-dependent and resulted in weak responses in a difficult task.

Physiological synchrony in supportive discussions: An examination of co-rumination, relationship type, and heterogeneity.

During times of stress, we look to close others for support. Social support conversations are critical for relationship maintenance and well-being. Yet, certain ways of talking about problems-such as co-ruminating-can exacerbate stress. Since social support and co-rumination are both dyadic processes, it is important to examine physiological responses during these conversations in a dyadic manner. Little research has examined physiological synchrony of the sympathetic nervous system (SNS) during social support conversations or co-ruminative conversations. The current research capitalizes on an experimental manipulation of co-rumination using a sample of close friends (147 dyads) and romantic partners (113 dyads) to examine physiological covariation in the context of support. Across both samples, dyads exhibited significant physiological covariation in pre-ejection period reactivity (PEP). Contrary to our hypothesis, dyads in the co-rumination condition did not show more covariation. Close friend dyads did, however, exhibit more covariation as compared to romantic dyads. We also found significant variability in physiological covariation across dyads, with a minority of dyads exhibiting negative covariation of PEP reactivity. The homogeneity of the samples limits the generalizability of the findings and highlights the need for more diverse samples in future work. These findings underline the need for further exploration into the mechanisms that contribute to distinct patterns of physiological synchrony, the conditions in which negative synchrony occurs, and what predicts especially strong positive synchrony. This work extends our understanding of physiological synchrony of the sympathetic nervous system during support conversations and emphasizes the importance of considering heterogeneity in physiological processes.

Noise annoys-But personal choice can attenuate noise effects on cardiac response reflecting effort.

Since personal choice fosters commitment and shields action execution against potentially conflicting influences, two laboratory experiments with university students (N = 228) tested whether engaging in action by personal choice versus external assignment of task characteristics moderates the effect of irrelevant acoustic noise on cardiovascular responses reflecting effort. Participants who could personally choose the stimulus color of moderately difficult cognitive tasks were expected to be shielded against the irrelevant noise. By contrast, when the stimulus color was externally assigned, we predicted receptivity for the irrelevant noise to be high. As expected, in both experiments, participants in the assigned color condition showed stronger cardiac pre-ejection period reactivity during task performance when exposed to noise than when working in silence. On the contrary, participants who could choose the stimulus color were shielded against the noise effect on effort. These findings conceptually replicate and extend research on the action shielding effect by personal choice and hold practical implications for occupational health.

The power of personal control: Task choice attenuates the effect of implicit sadness on sympathetically mediated cardiac response.

Implicitly processed pictures of facial expressions of emotions have been found to systematically influence sympathetically mediated cardiovascular reactivity during task performance. According to the Implicit-Affect-Primes-Effort model, this happens because different affect primes activate the concepts of performance ease versus performance difficulty. Grounded in a recent action shielding model, our laboratory experiment (N = 129 university students) tested whether engaging in action by personal choice can immunize against those implicit affective influences on effort. Participants worked on an objectively difficult cognitive task, which was either externally assigned or ostensibly personally chosen. As predicted, participants in the assigned task condition showed weaker cardiac pre-ejection period reactivity during task performance, reflecting disengagement, when they were primed with sadness than when they were exposed to anger primes. Most relevant, this affect prime effect disappeared when participants could ostensibly choose their task themselves. These findings replicate previous research on implicit affect's impact on sympathetically mediated cardiac response and extend the literature on action shielding by personal choice effects to implicit affective influences on action execution.

Can personal task choice shield against fear and anger prime effects on effort? A study on cardiac response

This experiment tested whether personal task choice can shield against implicit affective influences on sympathetically mediated cardiovascular response, reflecting effort. Participants were N = 121 healthy university students who completed a moderately difficult memory task with integrated briefly flashed and masked fear vs. anger primes. Half of the participants believed they could choose between an attention and a memory task, while the other half was automatically assigned to the task. Replicating previous research, we expected an influence of the affect primes on effort when the task was externally assigned. By contrast, when participants were given a task choice, we predicted strong action shielding and thus a weak implicit affect effect on resource mobilization. As expected, participants in the assigned task condition showed stronger cardiac pre-ejection period reactivity when exposed to fear primes than when processing anger primes. Importantly, this affect prime effect disappeared when participants could ostensibly choose the task. These findings add to other recent evidence for action shielding by personal task choice and importantly extend this effect to implicit affective influences on cardiac reactivity during task performance.

Is cognitive conflict really effortful? Conflict priming and shielding effects on cardiac response.

Two experiments with N=221 university students investigated the impact of primed cognitive conflict on effort assessed as cardiac response in tasks that were not conflict-related themselves. Manifest cognitive conflict in cognitive control tasks is confounded with objective response difficulty (e.g., in incongruent Stroop task trials). This makes conclusions about the effortfulness of cognitive conflict itself difficult. We bypassed this problem by administrating pictures of congruent versus incongruent Stroop task stimuli as conflict primes. As predicted, primed cognitive conflict increased cardiac pre-ejection period (PEP) responses in an easy attention task in Experiment 1. Accordingly, cognitive conflict itself is indeed effortful. This effect was replicated in an easy short-term memory task in Experiment 2. Moreover, as further predicted, the primed cognitive conflict effect on PEP reactivity disappeared when participants could personally choose task characteristics. This latter effect corresponds to other recent evidence showing that personal action choice shields against incidental affective influences on action execution and especially on effort-related cardiovascular response.

Effects of an attachment-based intervention on autonomic regulation among opioid-exposed infants.

Little is known about whether postnatal intervention enhances autonomic regulation among infants at risk for dysregulation due to prenatal opioid exposure. The present study evaluated the effects of modified Attachment Behavioral Catch-up (mABC) on autonomic regulation for opioid-exposed infants in a pilot randomized clinical trial. We hypothesized that, compared to a control intervention (modified Developmental Education for Families [mDEF]), mABC would be associated with higher resting respiratory sinus arrhythmia (RSA) and pre-ejection period (PEP) as well as greater reactivity to and recovery from a social stressor (Still-Face Paradigm). Pregnant or peripartum women receiving opioid agonist therapy (61 mothers of 64 infants; final N=36 infants) were randomly assigned to mABC or mDEF, 12-session home visiting programs beginning in the third trimester; mABC targets sensitive parenting, and mDEF targets cognitive and motor development. mABC was associated with significantly greater RSA reactivity and marginally greater PEP reactivity. In models accommodating missing data, mABC was additionally associated with significantly greater RSA recovery. In sensitivity analyses removing siblings, mABC predicted significantly enhanced PEP reactivity. Overall, in these preliminary analyses, mABC was associated with healthier autonomic regulation during a social stressor than mDEF. Thus, mABC may be a promising strategy to promote autonomic regulation among opioid-exposed infants through parenting intervention.

Incidental affective influences on effort-related cardiac response: The critical role of choosing task characteristics

This experiment tested whether personal choice vs. external assignment of task characteristics moderates the effect of incidental affective stimulation on effort-related cardiovascular response. We expected strong action shielding and low receptivity for incidental affective influences when participants could choose themselves the stimulus color of an easy memory task. By contrast, when the stimulus color was assigned, we expected weak action shielding and high receptivity. As expected, participants in the assigned color condition showed stronger cardiac pre-ejection period reactivity when exposed to sad music than when exposed to happy music during task performance. These music effects did not appear among participants who could personally choose the stimulus color. Our results replicate previous research by showing that personal choice leads to action shielding, whereas individuals remain receptive for affective influences during volition when task characteristics are assigned.

Physiological correlates of support for self-expansion and links to goal pursuit in retirement.

Partner support for self-expansion has been associated with long-term health and retirement satisfaction, yet the underlying physiological correlates are unknown. We predicted that partner support for self-expansion would be associated with short-term physiology and behavior as well as long-term goal pursuit. And 100 couples with at least one retiree within 2 years of retirement visited the laboratory and had a discussion of the retirees' future goals for retirement. We recorded behaviors and physiological responses during the discussion, assessed immediate feelings of capability afterwards, and then assessed goal pursuit one year later. Laboratory results indicated that partner support for self-expansion was linked to increased stroke volume reactivity in the support-recipient (suggesting a greater challenge response), which in turn predicted greater feelings of capability of accomplishing the goal, particularly for males. In addition, decreases in the support-provider's pre-ejection period reactivity (greater sympathetic arousal) during the discussion were associated with greater partner support for self-expansion in the lab, suggesting that support providers offer greater levels of support when they exhibit greater physiological signs of task engagement. Longitudinal follow-up results indicated that immediate feelings of capability of accomplishing the goal following a discussion about that goal predicted goal pursuit 1 year later. This research leverages a dyadic design and a multi-method approach (involving physiology, observed behavior, and perceptions) to show that couple members' physiology during goal discussions has long-term implications for a support-recipient's ability to accomplish goals.

Autonomic reactivity to social rejection, peer difficulties, and the buffering effects of adolescent friendships following early psychosocial deprivation.

Autonomic nervous system reactivity has been posited to be a mechanism contributing to social and emotional problems among children exposed to early adversity. Leveraging data from the Bucharest Early Intervention Project, a longitudinal randomized controlled trial of foster care versus institutional care of abandoned children in Romania, we assessed whether altered sympathetic reactivity to peer rejection feedback in early adolescence mediated the relation between early institutional rearing and peer problems in later adolescence. We also assessed whether adolescent friendship quality or randomized placement in foster care early in life moderated these associations. Participants include 68 institutionalized children randomized to care as usual, 68 institutionalized children randomized to foster care, and 135 never-institutionalized children. At age 12, participants reported friendship quality with respect to a best friend and completed a social rejection task while electrocardiogram and impedance cardiography were recorded. Sympathetic nervous system reactivity to rejection feedback was assessed using preejection period (PEP). At ages 12 and 16, peer problems were reported by parents. Mediation analysis revealed that less PEP reactivity to social rejection at age 12 partially mediated the association between early institutionalization and greater peer problems at age 16. Further moderated mediation analysis revealed that this indirect effect was evidenced among previously institutionalized youths with low, but not high, quality friendships. We did not observe foster care intervention effects. These findings suggest that altered sympathetic reactivity to social rejection might be a mechanism linking early institutionalization to social difficulties into adolescence, however, positive adolescent friendships may buffer these effects. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

β-Adrenergic Contributions to Emotion and Physiology During an Acute Psychosocial Stressor.

β-Adrenergic receptor signaling, a critical mediator of sympathetic nervous system influences on physiology and behavior, has long been proposed as one contributor to subjective stress. However, prior findings are surprisingly mixed about whether β-blockade (e.g., propranolol) blunts subjective stress, with many studies reporting no effects. We reevaluated this question in the context of an acute psychosocial stressor with more comprehensive measures and a larger-than-typical sample. We also examined the effects of β-blockade on psychophysiological indicators of sympathetic and parasympathetic nervous system reactivity, given that β-blockade effects for these measures specifically under acute psychosocial stress are not yet well established. In a double-blind, randomized, placebo-controlled study, 90 healthy young adults received 40 mg of the β-blocker propranolol or placebo. Participants then completed the Trier Social Stress Test, which involved completing an impromptu speech and difficult arithmetic in front of evaluative judges. Self-reported emotions and appraisals as well as psychophysiology were assessed throughout. Propranolol blunted Trier Social Stress Test preejection period reactivity (b = 9.68, p = .003), a marker of sympathetic nervous system activity, as well as salivary α-amylase reactivity (b = -0.50, p = .006). Critically, propranolol also blunted negative, high arousal emotions in response to the stressor (b = -0.22, p = .026), but cognitive appraisals remained intact (b values < -0.17, p values > .10). These results provide updated experimental evidence that β-adrenergic blockade attenuates negative, high arousal emotions in response to a psychosocial stressor while also blunting sympathetic nervous system reactivity. Together, these findings shed light on the neurophysiological mechanisms by which stressors transform into the subjective experience we call "stress."Trial Registration: ClinicalTrials.gov Identifier: NCT02972554.

Motivated but not engaged: The implicit achievement motive requires difficult or unclear task difficulty conditions to exert an impact on effort

Integrating the achievement motive literature and motivational intensity theory, we expected the implicit achievement motive (nAch) to directly determine effort mobilization when task difficulty is unclear. However, nAch should interact with task difficulty in determining effort mobilization when task difficulty is clear. Participants worked on an easy versus difficult memory task (Study 1) or a clear versus unclear arithmetic task (Study 2). We used the Picture-Story-Exercise to assess nAch and pre-ejection period (PEP) to operationalize effort. As predicted, PEP reactivity was strong in the difficult-high-nAch condition and in the unclear-high-nAch condition but low in the other three conditions. Supporting motivational intensity theory, our results showed that nAch requires difficult or unclear task conditions to exert a noticeable impact on effort.

Effortful listening: Sympathetic activity varies as a function of listening demand but parasympathetic activity does not

Research on listening effort has used various physiological measures to examine the biological correlates of listening effort but a systematic examination of the impact of listening demand on cardiac autonomic nervous system activity is still lacking. The presented study aimed to close this gap by assessing cardiac sympathetic and parasympathetic responses to variations in listening demand. For this purpose, 45 participants performed four speech-in-noise tasks differing in listening demand—manipulated as signal-to-noise ratio varying between +23 dB and -16 dB—while their pre-ejection period and respiratory sinus arrythmia responses were assessed. Cardiac responses showed the expected effect of listening demand on sympathetic activity, but failed to provide evidence for the expected listening demand impact on parasympathetic activity: Pre-ejection period reactivity increased with increasing listening demand across the three possible listening conditions and was low in the very high (impossible) demand condition, whereas respiratory sinus arrythmia did not show this pattern. These findings have two main implications. First, cardiac sympathetic responses seem to be the more sensitive correlate of the impact of task demand on listening effort compared to cardiac parasympathetic responses. Second, very high listening demand may lead to disengagement and correspondingly low effort and reduced cardiac sympathetic response.

Explicit achievement motive strength determines effort-related myocardial beta-adrenergic activity if task difficulty is unclear but not if task difficulty is clear

Work on physiological and other behavioral correlates of motives often assumes that motives exert a direct effect on behavior once activated. Motivational intensity theory, however, suggests that this does not always apply. In the context of task engagement, motive strength should exert a direct effect on myocardial beta-adrenergic activity if task difficulty is unclear, but not if task difficulty is known. The presented study tested this prediction for the impact of the explicit achievement motive on myocardial beta-adrenergic activity—assessed as pre-ejection period (PEP) reactivity during task performance. Seventy-eight participants performed one of two versions of a mental arithmetic task. After having completed the achievement motive scale of the Personality Research Form, participants were either informed about the difficulty of the task or not before working on it. Participants' PEP reactivity during task performance provided evidence for the predicted moderating impact of clarity of task difficulty: PEP reactivity increased with increasing achievement motive strength if task difficulty was unclear, but not if it was clear. These findings demonstrate that the explicit achievement motive impact on myocardial beta-adrenergic activity is moderated by clarity of task difficulty and suggest that motive strength does not always translate into direct effects on physiology and behavior.

Onset of substance use: Deviant peer, sex, and sympathetic nervous system predictors.

We evaluated whether the association between deviant peer affiliation and onset of substance use is conditional upon sex and sympathetic nervous system (SNS) reactivity as measured by pre-ejection period (PEP). Community-sampled adolescents (N = 251; M = 15.78 years; 53% female; 66% White, 34% Black) participated in three waves. PEP reactivity was collected during a mirror star-tracer stress task. Alcohol, marijuana, tobacco, or any substance use, as well as binge drinking and sexual activity involving substance use were outcomes predicted by affiliation with deviant peers and two- and three-way interactions with sex and PEP reactivity. Probability of substance use increased over time, but this was amplified for adolescents with greater deviant peer affiliation in conjunction with blunted PEP reactivity. The same pattern of results was also found for prediction of binge drinking and sexual activity involving substance use. Findings are discussed in the context of biosocial models of adolescent substance use and health risk behaviors.

Latent profiles of children's autonomic nervous system reactivity early in life predict later externalizing problems.

Prior researchers have observed relations between children's autonomic nervous system reactivity and externalizing behavior problems, but rarely considers the role of developmentally regulated changes in children's stress response systems. Using growth mixture modeling, the present study derived profiles of parasympathetic nervous system reactivity (as indicated by respiratory sinus arrhythmia (RSA)) and sympathetic nervous system reactivity (as indicated by pre-ejection period (PEP)) from low income, primarily Mexican American children measured repeatedly from infancy through age 5 (N=383) and investigated whether profiles were associated with externalizing problems at age 7. Analyses identified two profiles of RSA reactivity (reactive decreasing and U-shaped reactivity) and three profiles of PEP reactivity (blunted/anticipatory reactivity, reactive decreasing, non-reactive increasing). Compared to children with an RSA profile of reactive decreasing, those with an RSA profile of U-shaped reactivity had marginally higher externalizing problems, however, this difference was not statistically significant. Children who demonstrated a profile of blunted/anticipatory PEP reactivity had significantly higher externalizing problems compared to those with a profile of non-reactive increasing, likely related to the predominantly male composition of the former profile and predominantly female composition of the latter profile. Findings contribute to our understanding of developmental trajectories of ANS reactivity and highlight the utility of a longitudinal framework for understanding the effects of physiological risk factors on later behavior problems.

Investigating the Influences of Task Demand and Reward on Cardiac Pre-Ejection Period Reactivity During a Speech-in-Noise Task.

Objectives:Effort investment during listening varies as a function of task demand and motivation. Several studies have manipulated both these factors to elicit and measure changes in effort associated with listening. The cardiac pre-ejection period (PEP) is a relatively novel measure in the field of cognitive hearing science. This measure, which reflects sympathetic nervous system activity on the heart, has previously been implemented during a tone discrimination task but not during a speech-in-noise task. Therefore, the primary goal of this study was to explore the influences of signal to noise ratio (SNR) and monetary reward level on PEP reactivity during a speech-in-noise task.Design:Thirty-two participants with normal hearing (mean age = 22.22 years, SD = 3.03) were recruited at VU University Medical Center. Participants completed a Dutch speech-in-noise test with a single-interfering-talker masking noise. Six fixed SNRs, selected to span the entire psychometric performance curve, were presented in a block-wise fashion. Participants could earn a low (€0.20) or high (€5.00) reward by obtaining a score of ≥70% of words correct in each block. The authors analyzed PEP reactivity: the change in PEP measured during the task, relative to the baseline during rest. Two separate methods of PEP analysis were used, one including data from the whole task block and the other including data obtained during presentation of the target sentences only. After each block, participants rated their effort investment, performance, tendency to give up, and the perceived difficulty of the task. They also completed the need for recovery questionnaire and the reading span test, which are indices of additional factors (fatigue and working memory capacity, respectively) that are known to influence listening effort.Results:Average sentence perception scores ranged from 2.73 to 91.62%, revealing a significant effect of SNR. In addition, an improvement in performance was elicited by the high, compared to the low reward level. A linear relationship between SNR and PEP reactivity was demonstrated: at the lower SNRs PEP reactivity was the most negative, indicating greater effort investment compared to the higher SNRs. The target stimuli method of PEP analysis was more sensitive to this effect than the block-wise method. Contrary to expectations, no significant impact of reward on PEP reactivity was found in the present dataset. Also, there was no physiological evidence that participants were disengaged, even when performance was poor. A significant correlation between need for recovery scores and average PEP reactivity was demonstrated, indicating that a lower need for recovery was associated with less effort investment.Conclusions:This study successfully implemented the measurement of PEP during a standard speech-in-noise test and included two distinct methods of PEP analysis. The results revealed for the first time that PEP reactivity varies linearly with task demand during a speech-in-noise task, although the effect size was small. No effect of reward on PEP was demonstrated. Finally, participants with a higher need for recovery score invested more effort, as shown by average PEP reactivity, than those with a lower need for recovery score.

Stress system reactivity moderates the association between cumulative risk and children's externalizing symptoms

This study examined children's stress system reactivity via the autonomic nervous system (ANS) and hypothalamic pituitary adrenal axis (HPAA) during an acute stressor as moderators of predicted relations between cumulative risk (CR) and mental health symptoms in a sociodemographically diverse sample of young children (n = 58). We employed a reliable stressor paradigm to allow assessment of individual differences in respiratory sinus arrhythmia (RSA) and pre-ejection period (PEP), indexing ANS reactivity, and salivary cortisol, indexing HPAA reactivity. Children's behaviours were assessed using the Child Behaviour Checklist (CBCL). Cumulative risk was indexed by eight parent-reported sociodemographic and psychosocial risk factors. There was a significant main effect of CR on externalizing but not internalizing behaviours. Significant moderations emerged showing that among children with high CR, less RSA withdrawal during the acute stressor and less cortisol recovery following the stressor were associated with to greater externalizing behaviours. Among children with low CR, RSA and cortisol recovery were unrelated to internalizing or externalizing symptoms. Cortisol and PEP reactivity were not significant moderators. Results highlight the relevance of stress system function for understanding differential susceptibility to the early emergence of externalizing symptoms, linked to cumulative risk exposure.

Distribution, Stability, and Continuity of Autonomic Nervous System Responsivity at 18- and 36-Months of Age.

Cardiac autonomic nervous system (ANS) measures, respiratory sinus arrhythmia (RSA) and preejection period (PEP), are valid and reliable indicators of children's sensitivity to their environment; however, there are few studies of ANS measures in children less than three years of age. This study's aim was to summarize the distributions, stability, and continuity of RSA and PEP measures during resting, challenge, and reactivity for children at 18- and 36-months. This was a cohort study of racially- and ethnically-diverse, low-income children who completed a developmentally challenging protocol while we simultaneously assessed their RSA and PEP at 18-months (N = 134) and 36-months (N = 102). The ANS resting, challenge, and reactivity measures at 18- and 36-months of age were normally distributed. The RSA resting (r = 0.29), RSA challenge (r = 0.44), PEP resting (r = 0.55) and PEP challenge (r = 0.58) measures were moderately stable but RSA (r = 0.01) and PEP reactivity (r = 0.02) were not stable from 18- to 36-months of age. There was no continuity in the ANS measures from 18- to 36-months of age with statistically significant changes in sample means for all of the ANS measures. These developmental changes in ANS are shown at the sample level but there are individual differences in ANS responses from 18- to 36-months that may be affected by adversity or protective factors experienced early in life.