Fearful Temperament Research Articles

Assessing anxiety problems in a community sample during toddlerhood: The impact of child temperament and maternal intrusiveness

Previous research indicates that child temperament and maternal behaviors are related to internalizing behaviors in children. We assessed whether maternal intrusiveness (MI) observed at 10-months would moderate the impact of temperamental fear and the impact of inhibitory control (IC) at 24 months on anxiety problems at 36 months. A mother-child interaction task was coded for MI. Behavioral tasks were given to assess children’s IC. Parents completed questionnaires about their children’s temperamental fear and anxiety problems. Results showed that greater temperamental fear reported at 24 months predicted greater anxiety problems reported at 36 months, regardless of MI levels. Lower levels of IC at 24 months predicted more anxiety problems reported at 36 months when children experienced greater MI. These findings illustrate the importance of examining both intrinsic and extrinsic factors, independently and interactively, that contribute to children’s anxiety problems in toddlerhood.

Math anxiety and math motivation in online learning during stress: The role of fearful and avoidance temperament and implications for STEM education

Students’ math motivation can predict engagement, achievement, and career interest in science, technology, engineering, and mathematics (STEM). However, it is not well understood how personality traits and math anxiety may be linked to different types or qualities of math motivation, particularly during high-stress times such as the COVID-19 pandemic. In this study, we examined how fearful or avoidant temperaments contribute to math anxiety and math motivations for college students during the COVID-19 pandemic. Ninety-six undergraduate students from a large public university were assessed on temperamental fear, math anxiety, and math motivation in an online math course. Results showed that higher levels of temperamental fear are directly linked to higher levels of math anxiety. In addition, temperamental fear is indirectly linked to higher levels of autonomous motivation (i.e., intrinsic motivation and identified regulation) and lower levels of controlled motivation (i.e., external regulation) through math anxiety. Results have implications for helping students at high risk for both high math anxiety and for low motivation to engage in math learning.

How much maternal sensitivity is adaptive: Fear temperament, high-intensity fear, and preschooler's behavioral problems

BackgroundThe current study focused on the role of temperament and parenting in contributing to high-intensity fear during toddlerhood and its impact on behavioral problems in the preschool age. MethodsA sample of 1292 low-income rural families were recruited, where infant fear temperament at 6 months old and toddler's fear expressions at 15 months old were observed and assessed. Maternal sensitivity was also observed and assessed at both time points. Mothers rated their children's behavioral problems at 36 months old. ResultsA path model revealed quadratic effects of maternal sensitivity on the development of high-intensity fear at 15 months, in that a moderate level of maternal sensitivity was linked with higher high-intensity fear for children with extra high temperamental fear, while high and low levels of maternal sensitivity were linked with higher high-intensity fear for those with extra low temperamental fear. A quadratic effect was also found, where high maternal sensitivity channeled toddlers with low normal fear towards internalizing behaviors at 36 months. Finally, a quadratic effect suggested that high maternal sensitivity increased the risks for externalizing behaviors at 36 months for toddlers with high versus low levels of high-intensity fear. LimitationsThe low-income, rural community sample limited study generalizability. ConclusionsThese findings speak to the complexity of person-environment interactions in the development of fear and associated behavioral problems, with implications for future research and intervention efforts.

Afraid to vomit? The relationship between temperamental fear, emetophobia symptoms, and the impact of sex.

Emetophobia, the specific phobia of vomiting (SPOV), is an anxiety disorder associated with persistent fear of emesis. The temperament of fear is evident in phobic and anxiety disorders, which behaviorally manifests through sensitivity in the fight, flight, freeze system (FFFS). The present study aimed to test specific associations between these constructs. Undergraduate students (N= 186) completed self-report measures assessing symptoms of emetophobia, the FFFS, and general anxiety. Correlational analyses were used to test initial relations, followed by regression analyses to assess unique contribution of temperamental fear to the emetophobia symptom experience. Significant positive correlations were found between emetophobia symptoms with anxiety symptoms and the overall temperament of fear. However, only the fight response of the FFFS was significantly associated with symptoms of emetophobia. Further regression analyses demonstrated that the fight response did not uniquely predicted emetophobia symptoms above and beyond anxiety. However, post-hoc analyses illustrated sex moderated the relationship between temperamental fear and emetophobia symptoms, such that the relationship was significantly stronger for male participants than female participants. Results of this study expand upon the current conceptualization of emetophobia to incorporate underlying temperamental vulnerabilities and sex differences, which may function to exacerbate and/or maintain symptoms. Keywords: emetophobia; specific phobia of vomiting (SPOV); fight, flight, freeze system (FFFS); fight, flight, freeze questionnaire (FFFQ); sex differences

Disaster Exposure and Temperament as Predictors of Adolescent Substance Use

ABSTRACT Objective Children who have been exposed to a natural disaster in their lifetime comprise a significant population with specific risks and vulnerabilities, particularly for at-risk youth. The goal of the current study was to examine the role that severity of disaster exposure plays in determining the timing of alcohol and marijuana use initiation and the frequency of use four years later in a sample of at-risk, aggressive youth exposed to a devastating tornado. Of further interest was the examination of the moderating effect of temperamental fear and inhibitory control. Method Three hundred and forty-six youth (M age = 11.33; 65% boys; 77.5% African-Americans, 18.3% Caucasian, 1.7% Hispanic) initially recruited for a prevention program for at-risk youth were followed for 4 years after a tornado. Cox PH regressions were conducted to predict timing of alcohol and marijuana use initiation. Zero-inflated negative binomial regressions were used to predict frequency of alcohol and marijuana use 4 years after the tornado. Results Disaster exposure severity was predictive of frequency of marijuana use four years after the tornado, but exposure alone was not predictive of initiation. Exposure severity predicted increases in risk for alcohol use initiation only for youth high in fear. Additionally, greater levels of inhibitory control protected youth from earlier alcohol use initiation. Conclusions Findings highlight a need to research the initiation and frequency of use for substances individually, while also assessing the needs of youth exposed to natural disasters with both their degree of disaster exposure and specific temperamental characteristics in mind.

Infant temperamental fear, pupil dilation, and gaze aversion from smiling strangers.

In childhood, higher levels of temperamental fear-an early-emerging proclivity to distress in the face of novelty-are associated with lower social responsivity and greater social anxiety. While the early emergence of temperamental fear in infancy is poorly understood, it is theorized to be driven by individual differences in reactivity and self-regulation to novel stimuli. The current study used eye tracking to capture infants' (N=124) reactions to a video of a smiling stranger-a common social encounter-including infant gaze aversions from the stranger's face (indexing arousal regulation) and pupil dilation (indexing physiological reactivity), longitudinally at 2, 4, 6, and 8 months of age. Multilevel mixed-effects models indicated that more fearful infants took more time to look away from a smiling stranger's face than less fearful infants, suggesting that high-fear infants may have slower arousal regulation. At 2 and 4 months, more fearful infants also exhibited greater and faster pupil dilation before gaze aversions, consistent with greater physiological reactivity. Together, these findings suggest that individual differences in infants' gaze aversions and pupil dilation can index the development of fearful temperament in early infancy, facilitating the identification of, and interventions for, risk factors to social disruptions.

Are fearful boys at higher risk for anxiety? Person-centered profiles of toddler fearful behavior predict anxious behaviors at age 6.

Dysregulated fear (DF), the presence of fearful behaviors in both low-threat and high-threat contexts, is associated with child anxiety symptoms during early childhood (e.g., Buss et al., 2013). However, not all children with DF go on to develop an anxiety disorder (Buss and McDoniel, 2016). This study leveraged the data from two longitudinal cohorts (N = 261) to (1) use person-centered methods to identify profiles of fearful temperament, (2) replicate the findings linking DF to anxiety behaviors in kindergarten, (3) test if child sex moderates associations between DF and anxiety behaviors, and (4) examine the consistency of findings across multiple informants of child anxiety behaviors. We identified a normative fear profile (low fear in low-threat contexts; high fear in high-threat contexts), a low fear profile (low fear across both low- and high-threat contexts) and a DF profile (high fear across both low- and high-threat contexts). Results showed that probability of DF profile membership was significantly associated with child self-reported overanxiousness, but not with parent-reported overanxiousness. Associations between DF profile membership and overanxiousness was moderated by child sex such that these associations were significant for boys only. Additionally, results showed that probability of DF profile membership was associated with both parent-reported social withdrawal and observations of social reticence, but there were no significant associations with child self-report of social withdrawal. Results highlight the importance of considering person-centered profiles of fearful temperament across different emotion-eliciting contexts, and the importance of using multiple informants to understand associations with temperamental risk for child anxiety.

Fearful Temperament, Catastrophizing, and Internalizing Symptoms in Clinically Anxious Youth.

A fearful temperament in childhood is associated with child internalizing symptoms. However, the cognitive mechanisms explaining this association are poorly understood. We examined the effects of child fearful temperament on child internalizing symptoms and the underlying role of catastrophizing cognitions among clinically anxious youth. Children (N = 105; M age = 10.09 years, SD = 1.22; 56.7% female; 62% ethnic minority) completed a diagnostic interview; self-report measures of temperament, catastrophizing, and internalizing symptoms; and behaviorally-indexed measures of catastrophizing and anxiety. Indirect effects were found for child fearful temperament on child self-reported internalizing symptoms by way of self-reported (but not behaviorally-indexed) catastrophizing cognitions. Models predicting behaviorally-indexed child anxiety were not significant. Our findings suggest that targeting fearful temperament during childhood before catastrophizing cognitions develop may have clinical utility. Likewise, among children temperamentally at-risk, addressing catastrophic cognitions may prevent later internalizing psychopathology.

The interplay between parenting and environmental sensitivity in the prediction of children's externalizing and internalizing behaviors during COVID-19.

The interplay of parenting and environmental sensitivity on children's behavioral adjustment during, and immediately after, the COVID-19 lockdown restrictions was investigated in two longitudinal studies involving Italian preschoolers (Study 1, N = 72; 43% girls, Myears = 3.82(1.38)) and primary school children (Study 2, N = 94; 55% girls, Myears = 9.08(0.56)). Data were collected before and during the first-wave lockdown (Studies 1 and 2) and one month later (Study 1). Parental stress and parent-child closeness were measured. Markers of environmental sensitivity in children were temperamental fearfulness and Sensory Processing Sensitivity. Results showed little change in externalizing and internalizing behaviors over time, but differences emerged when considering parenting and children's environmental sensitivity. In preschoolers, greater parenting stress was related to a stronger increase in internalizing and externalizing behaviors, with children high in fearful temperament showing a more marked decrease in externalizing behaviors when parenting stress was low. In school-aged children, parent-child closeness emerged as a protective factor for internalizing and externalizing behaviors during COVID-19, with children high in Sensory Processing Sensitivity showing a marked decrease in internalizing behaviors when closeness was high. Implications for developmental theory and practice in times of pandemic are discussed.

Parent-to-Child Anxiety Transmission Through Dyadic Social Dynamics: A Dynamic Developmental Model.

The intergenerational transmission of psychopathology is one of the strongest known risk factors for childhood disorder and may be a malleable target for prevention and intervention. Anxious parents have distinct parenting profiles that impact socioemotional development, and these parenting effects may result in broad alterations to the biological and cognitive functioning of their children. Better understanding the functional mechanisms by which parental risk is passed on to children can provide (1) novel markers of risk for socioemotional difficulties, (2) specific targets for intervention, and (3) behavioral and biological indices of treatment response. We propose a developmental model in which dyadic social dynamics serve as a key conduit in parent-to-child transmission of anxiety. Dyadic social dynamics capture the moment-to-moment interactions between parent and child that occur on a daily basis. In shaping the developmental trajectory from familial risk to actual symptoms, dyadic processes act on mechanisms of risk that are evident prior to, and in the absence of, any eventual disorder onset. First, we discuss dyadic synchrony or the moment-to-moment coordination between parent and child within different levels of analysis, including neural, autonomic, behavioral, and emotional processes. Second, we discuss how overt emotion modeling of distress is observed and internalized by children and later reflected in their own behavior. Thus, unlike synchrony, this is a more sequential process that cuts across levels of analysis. We also discuss maladaptive cognitive and affective processing that is often evident with increases in child anxiety symptoms. Finally, we discuss additional moderators (e.g., parent sex, child fearful temperament) that may impact dyadic processes. Our model is proposed as a conceptual framework for testing hypotheses regarding dynamic processes that may ultimately guide novel treatment approaches aimed at intervening on dyadically linked biobehavioral mechanisms before symptom onset.

Maternal respiratory sinus arrhythmia contextualizes the relation between maternal anxiety and overprotective parenting.

This current study examined maternal characteristics that predict the use of overprotective parenting in mothers of toddlers. Maternal respiratory sinus arrhythmia (RSA) reactivity was tested as a moderator of the relation between maternal anxiety and overprotective parentig. Mothers (n = 151) and their 2-year-old toddlers participated in a laboratory visit and returned for a follow-up visit 1 year later. At child age 2, mothers reported their own anxiety. Mothers' RSA reactivity was measured between a resting baseline and a standardized laboratory task, and overprotective parenting was observed in that task. Toddler fearful temperament (FT) was observed in a separate standardized task as well as reported by mothers. At child age 3, mothers' overprotective parenting behaviors were observed according to the same procedures so change from age 2 could be measured. Results revealed that maternal anxiety and maternal RSA at age 2 interacted to predict relative increases in overprotective parenting behaviors at age 3. At low levels of RSA reactivity, reflecting RSA suppression, maternal anxiety predicted lower levels of overprotective parenting. At high levels of RSA reactivity, reflecting RSA augmentation, maternal anxiety predicted higher levels of overprotective parenting. Our results suggest that RSA suppression may protect mothers with anxiety symptoms from engaging in overprotective parenting, whereas RSA augmentation may put mothers with anxiety symptoms at risk for engaging in overprotective parenting. Findings indicate that the interaction of multiple parental traits should be considered when working with parents and families on parenting behavior. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Fearful temperament in middle childhood predicts adolescent attention bias and anxiety symptoms: The moderating role of frontal EEG asymmetry.

The current study provided first analyses of the moderating effect of baseline-to-task frontal EEG asymmetry on the associations between 9-year fearful temperament and adolescent attention bias to threat as well as anxiety symptoms. Participants include a community sample of 122 children (60 boys, 62 girls; Mage = 14.66 years; Range = 11.82-18.13 years). Baseline-to-task frontal EEG asymmetry at age 9 moderated the relation between fearful temperament at age 9 and adolescent anxiety symptoms. Specifically, fearful temperament predicted adolescent anxiety symptoms when children showed greater right activation from baseline to an executive function task, but not greater left activation. Baseline-to-task frontal EEG asymmetry moderated the association between fearful temperament and sustained (i.e., stimulus onset asynchrony is 1250 ms) but not automatic attention bias (i.e., stimulus onset asynchrony is 500 ms). Children with greater left frontal activation from baseline to task more efficiently direct attention away from threat. Adolescent automatic attention bias to threat was related to concurrent anxiety symptoms. These findings illustrate the importance of considering frontal EEG asymmetry to shape how fearful children process threat and to influence their behavioral problems.

Expressions of positive and negative shyness in preschool-age children: Temperamental correlates and visual attention to emotions

Recent empirical evidence shows heterogeneity in the expression of shyness in children. Some children tend to express their shyness displaying positive affect along with gaze aversions (positive shyness), whereas others display more negative emotional reactions accompanied by gaze aversions (negative shyness). Temperamental differences in approach–avoidance tendencies are likely to explain these differences in shyness expression in children and influence their visual attention to social stimuli, yet little empirical attention has been devoted to these associations. Our study examined the temperamental profile (approach, fear, and inhibitory control) associated with positive and negative shyness and the relation between expression of shyness and attention to social stimuli in 47 children aged 3–6 years. Children’s positive and negative expressions of shyness were assessed using a performance task. Visual attention to facial emotional expressions was measured with the dot - probe task, and temperament was measured with maternal reports. Positive shyness was found to be positively associated with temperamental dimensions of approach, inhibitory control, and fear. Positive shyness was significantly associated with attentional orientation to positive facial expressions and with less attentional avoidance of threatening facial expressions. Negative shyness was positively associated only with temperamental fear, and no associations were found with attention to social stimuli. Our study provides empirical support for the association between temperament and the multidimensional character of the expression of positive shyness and adds relevant evidence regarding the connection between the expression of shyness and attention to social stimuli.

Attention Biases to Threat in Infants and Parents: Links to Parental and Infant Anxiety Dispositions

Parent-to-child transmission of information processing biases to threat is a potential causal mechanism in the family aggregation of anxiety symptoms and traits. This study is the first to investigate the link between infants’ and parents’ attention bias to dynamic threat-relevant (versus happy) emotional expressions. Moreover, the associations between infant attention and anxiety dispositions in infants and parents were explored. Using a cross-sectional design, we tested 211 infants in three age groups: 5-to-7-month-olds (n = 71), 11-to-13-month-olds (n = 73), and 17-to-19-month-olds (n = 67), and 216 parents (153 mothers). Infant and parental dwell times to angry and fearful versus happy facial expressions were measured via eye-tracking. The parents also reported on their anxiety and stress. Ratings of infant temperamental fear and distress were averaged across both parents. Parents and infants tended to show an attention bias for fearful faces with marginally longer dwell times to fearful versus happy faces. Parents dwelled longer on angry versus happy faces, whereas infants showed an avoidant pattern with longer dwell times to happy versus angry expressions. There was a significant positive association between infant and parent attention to emotional expressions. Parental anxiety dispositions were not related to their own or their infant’s attention bias. No significant link emerged between infants’ temperament and attention bias. We conclude that an association between parental and infant attention may already be evident in the early years of life, whereas a link between anxiety dispositions and attention biases may not hold in community samples.

Bidirectional effects of toddler temperament and maternal overprotection on maternal and child anxiety symptoms across preschool.

Existing research highlights interactions among child temperament, parents' own anxiety symptoms, and parenting in predicting increased risk for anxiety symptom development. Theoretical models of child-elicited effects on parents have proposed that parents' behaviors are likely not independent of children's temperament; fearful children likely elicit more protective responses from parents and these parenting behaviors reinforces child anxiety and parents' own anxiety. The current study tests this model and examines whether there are bidirectional influences between early fearful temperament (i.e., dysregulated fear [DF]), maternal overprotection, and subsequent trajectories of maternal and child anxiety symptoms across early childhood. A total of 166 children and mothers participated in a multimethod, longitudinal study of temperament risk from 2 to 6 years. Results largely support our hypotheses, replicating and extending the prior literature. DF was associated with more maternal overprotective behavior, subsequent child anxiety symptoms, and maternal anxiety symptoms. Moreover, there were indirect (mediated) associations through maternal overprotective behavior and both child and mother anxiety symptoms. Results support the hypothesis that intergenerational transmission of anxiety was meditated through maternal behaviors and that the child-driven temperament effects are central to trajectories of child and maternal anxiety trajectories.

Fearful Temperament and Child Social Anxiety Symptoms: Clarifying the Influence of Maternal Punitive Responses.

Fearful temperament-the tendency to exhibit apprehension and/or avoidance in novel situations-is a well-established risk factor for childhood anxiety in general, and social anxiety in particular. Yet, there is little understanding of parent emotion socialization strategies that influence the association between fearful temperament and child social anxiety symptoms. The present investigation addresses this gap in the literature by examining maternal punitive responses to clinically anxious children's negative emotions as a moderator of the covariance between fearful temperament and social anxiety symptom severity. Clinically anxious children ages 8-12years (N = 105; 57.1% female; 61.9% racial/ethnic minority) and their mothers completed measures assessing child fearful temperament, maternal punitive emotion socialization responses, and child social anxiety symptoms. Children also participated in an anxiety-provoking speech task during which manifest social anxiety was coded by trained observers. Children's fearful temperament coupled with greater maternal punitive responses to children's negative emotions was associated with lower child-reported social anxiety symptoms. Models predicting manifest social anxiety were not significant. Maternal punitive responses to children's negative emotions may encourage clinically anxious youth to approach feared situations and therefore result in lower anxiety. Yet, the potentially negative effects of punitive responses on other aspects of anxious children's socioemotional development warrant scientific attention. Future research should examine the phenomenology of punitive parental responses among parents of anxious youth to better understand their effects on child behavior.

Self-Esteem, Self-Monitoring, and Temperamental Traits in Action: Who Is Involved in Humanitarian, Political, and Religious Non-profit Organizations?

Self-esteem, self-monitoring, and temperamental traits are important factors that influence human behavior. The purpose of the present study was to compare groups involved in humanitarian (n = 61), political (n = 68), and religious (n = 54) activities in terms of intergroup differences in self-esteem, self-monitoring, and temperamental traits. There are two research questions that we sought to address: “What are the relationships between self-esteem, self-monitoring, and temperamental traits among those involved in social, religious, and humanitarian aid activities?” and “Do temperamental traits affect self-esteem and self-monitoring among volunteers?” The study was conducted in Poland among adults aged 18 years and older, during meetings of six selected non-profit organizations, consisting of two organizations each in the humanitarian, political, and religious areas. The study used the Polish versions of the Rosenberg Self-esteem Scale, Snyders’ Self-Monitoring Scale, and the EAS Temperament Questionnaire. Volunteers of humanitarian organizations had the lowest self-esteem among all the examined groups. Politicians turned out to be more pragmatic than those involved in religious activities and humanitarian aid. Between the three examined groups, there were statistically significant differences in temperamental activity; the most active are those politically involved, followed by participants involved in humanitarian aid and religious activities. Moreover, volunteers involved in humanitarian aid reported a higher level of temperamental fear than those involved in political and religious activities. Furthermore, there were group differences in their reasons for social involvement. We discuss the potential sources of differences and consequences of outcomes for human resource practice in non-profit organizations.

Peer Victimization in Late Childhood Moderates the Relationship between Childhood Fear/Inhibition & Adolescent Externalizing Symptoms

ABSTRACT Objective Studies of the association between early childhood low temperamental fearfulness or behavioral inhibition (BI) and later externalizing symptoms are few and results are inconsistent, despite research from outside the temperament field that has linked fearlessness with externalizing problems. There is also a large literature showing that peer victimization (PV) predicts externalizing symptoms. However, no prior studies have examined the joint effect of low temperamental fearfulness/BI and PV on externalizing psychopathology. The current study examined the main and joint effects of low temperamental fearfulness/BI and PV on broad internalizing and externalizing problems, as well as more narrow forms of externalizing psychopathology. Method Participants included 559 children (86.5% white, 54% male) assessed at ages 3, 6, 9, and 12. Temperamental fearfulness/BI was assessed using laboratory observations at age 3. PV was assessed via semi-structured interviews at ages 6 and 9. Finally, internalizing and externalizing psychopathology were each assessed at ages 3 and 12. Results After accounting for sex, race, and age 3 symptomatology, the joint effect of low temperamental fearfulness/BI and PV predicted higher levels of externalizing problems overall and specific externalizing symptom domains, but not internalizing problems. Conclusion These results suggest that there is an association between low temperamental fearfulness/BI and later externalizing psychopathology, but that it depends on moderating factors such as PV.

Disturbed Social Information Processing as a Mechanism in the Development of Social Anxiety Disorder

AbstractSocial anxiety disorder (SAD) is one of the most common mental disorders and becomes chronic if left untreated. Even when it is treated, outcomes are less promising than for other anxiety disorders. Thus, many are interested in preventing SAD and in the mechanisms involved in the development of SAD. In this article, I propose in a new model that disturbances in social cognition (cognitive biases, emotion recognition and understanding, negative expectations) and dysregulated social emotions (social fear and self‐conscious emotional arousal) in toddlerhood and early childhood lead to avoidance and high levels of anxiety in social situations. When repeated over time, these impair daily functioning and result in a disorder. Biological factors (e.g., fearful temperament), environmental factors (e.g., parental mentalizing), and past experiences may be distal factors that contribute to the development of SAD via disturbed sociocognitive processing and dysregulated emotions. Based on this model, I conclude by describing clinical implications and recommendations for research.

Charting the physiological time course of help-seeking during late childhood: Patterns of individual difference

In this study, we explored whether variability in children’s physiological reactivity—respiratory sinus arrhythmia and electrodermal activity—predict concurrent and subsequent levels of children’s observed help-seeking (HS) from their mothers during a failure task. In addition, we tested whether children’s perceptions of maternal positivity pre-task (CPMP) and children’s fearful temperament moderate these effects. In a community sample of 101 mother–child dyads, children (8–12 years of age) underwent a repeated failure task while their respiratory sinus arrythmia and electrodermal activity were monitored; their HS behaviors were later coded. Multilevel path analyses indicated that high-fearful children increased their HS at the same time as and following increased physiological reactivity regardless of CPMP pre-task. Low-fearful children showed increases in HS at the same time as and following increased physiological reactivity only when they perceived their mothers’ affect to be positive. This study demonstrates children’s individual differences in the physiological underpinning of time-linked HS behaviors.