Emotion Regulation and Cognitive and Social Functioning in Early Development: The Interface between Neurophysiological and Behavioural Perspectives

Abstract

Research on the development of emotions and their function as indicators of psychological adjustment has increased dramatically in recent years. The importance of emotion recognition and regulation for understanding normal development and the development of psychopathology is now undeniable. From an early age, the ability to recognise and modulate emotional responses to cope appropriately with environmental demands is associated with cognitive, behavioural and social development. This chapter aims to critically review the research field of emotion regulation, its relationship to emotional intelligence and its contribution to cognitive and social functioning in young children (up to the age of six), placing a dual emphasis on the role of physiological systems in emotion regulation and on the interface between neurophysiological and behavioural perspectives. Challenges and future directions in emotion regulation research will be discussed.

1. Introduction

Over the past decades, there has been a surge of research interest in early childhood emotions. The first years of life appear to be the most optimal period for emotional development because of the brain processes that occur during this time. The brain’s structure, functions and connections are being established in response to environmental stimulation, so emotional experiences that happen early in life will have a profound impact on the development and ability to recognise and manage emotions appropriately [1].

Emotion regulation (ER) is a key element in children’s developmental outcomes, influencing cognition, behaviour and social interactions, and is closely related to emotional intelligence (EI). During childhood, appropriate ER strategies enable children to successfully communicate and cooperate with peers, adults and the environment [2]. These strategies are associated with cognitive functioning, behaviour and empathy processes [3, 4]. In view of the significant importance of emotions, alterations in emotional processing have been proposed as a transdiagnostic mechanism in child psychopathology (see [5] for a review).

The purpose of this chapter is to provide an overview of ER in early childhood (up to the age of six). In what follows, we will define ER and its relationship to EI, as well as explore ER strategies used by young children, discussing their adaptive value and their association with cognitive and behavioural outcomes. We will also examine the role of ER in childhood psychopathology. We will then present a narrative review of the evidence for the neurophysiological mechanisms underlying ER and its relationship to cognition and behaviour. For this purpose, the following terms were used in the literature search: (infant OR infancy OR child*) AND (“emotion* regulation”) AND (mri OR fmri OR fnirs OR nirs OR eeg OR erp OR vagal OR rsa). In addition, a manual search of the reference lists of the selected studies was conducted to identify additional studies that may have been of interest for this review. Finally, we will discuss future challenges and directions for ER research.

2. Emotional intelligence and emotion regulation

Emotional development begins early in life, as infants are already born with the ability to process and express different emotions (e.g. crying) [6]. In the first six years, emotional development is a fundamental aspect that influences cognition, behaviour and social functioning, as it allows children to adapt to different environments (e.g. school) and successfully establish interpersonal relationships throughout their life [7]. Early childhood is an extremely important period for children to learn and manage emotions, with research demonstrating that this period represents a critical window for the development of emotional competencies and self-regulation, with long-term consequences for academic, personal and social outcomes [8].

EI and ER are two research traditions that address emotion management across development. Although relatively independent, their relationship is well-established in the literature. High EI individuals manage their emotions at the earliest point in the emotion trajectory, have a larger repertoire of regulation strategies and are more flexible and successful in regulating their emotions [9]. Understanding emotions will allow their recognition and, consequently, the employment of adequate strategies to deal with different emotional states [10]. Research in early development also corroborates these findings and has shown that children with higher EI are better able to pay attention, are more engaged in school, have more positive relationships and are more empathic [11, 12]. In parallel, children who score higher in EI are also better at regulating aggressive behaviour [13].

EI refers to a set of skills (e.g. perception or regulation of emotions) that allow the recognition and understanding of emotions in oneself and others [14, 15]. These skills are consistent with the term ‘emotional competence’ (EC) employed in the developmental psychology literature [16]. Young children’s EC entails (i) the expression of emotions, (ii) knowledge of emotions in oneself and others and (iii) the ability to regulate their own and others’ emotional expressiveness and experience [17]. The ability to effectively regulate one’s emotional expressions (i.e. emotion regulation) is of great importance, especially in the preschool years, as it plays an important role in development due to its long-term impact on future adjustment [18].

2.1 Emotion regulation in early childhood

ER refers to the child’s ability to modulate emotional responses consciously or unconsciously [19]. It encompasses the intrinsic and extrinsic processes of monitoring, assessing and modifying emotional reactions, particularly concerning their timing and intensity, to achieve personal goals [20, 21]. By modifying the magnitude and/or type of their emotional experience or the emotion-evoking event [22], children can influence their emotions, depending on their valence (positive or negative), along with the situations and time when they are expressed [23]. This ability enables them to effectively navigate and adapt to different environments [24, 25]. According to Gross [22], ER strategies are organised around four temporal stages: (i) an internal or external event triggers an emotional response, (ii) attention is allocated to that event, (iii) an assessment of that event is made and (iv) a response is produced following the emotional experience of that event.

ER abilities grow rapidly in the early years and continue to grow throughout development [26]. In children aged between 1 and 3 years, ER abilities rely heavily on external social support, particularly from their parents and caregivers [27, 28, 29, 30, 31]. Alongside, various processes, such as language or executive functions (e.g. cognitive control), influence the development of ER, enabling children to recognise and label their emotional states, communicate their needs, seek support from others and appropriately respond to environmental demands [21, 27, 32, 33, 34, 35]. The increased awareness of others, supported by the development of the Theory of Mind abilities [36], adds a social dimension to emotions [37].

By the age of 3, emotion regulation significantly improves, as children can recognise basic emotions in others and adjust their behaviours in social interactions, as observed in an experimental task in which children were asked to assign an emotion to a cartoon character [38]. Behavioural control emerges along with the peak of aggressive behaviours, and young children become able to use effective ER strategies, such as delaying gratification, maintaining focus, using a lower voice and/or reducing motor behaviour, assessed in both social role-play tasks and parent report measures. [33]. Additional evidence, using story completion tasks to elicit emotion-related narratives, suggests that children begin to use antecedent-focused ER strategies (i.e. regulatory strategies that occur before or during emotion processing and are effective in modulating emotional responses, see [39]), such as cognitive reappraisal (e.g. the process of creating positive interpretations or perspectives of a stressful situation to reduce distress, see [40]), at age 3, and become more effective in using this strategy throughout childhood (around age 5) [41]. Between the ages of 4 and 6, children begin to grasp their internal experiences (e.g. memories, fears and wishes) and distinguish real emotional experiences from virtual ones [30, 34, 38, 42]. At the age of 6, they become increasingly able to cope with negative emotions and use distraction strategies (e.g. playing, drawing or singing) to manage them [37]. They also begin to control some maladaptive emotion regulation strategies, such as crying, wailing and shouting [42].

In terms of maladaptive strategies, two strategies have been consistently linked to adjustment problems: suppression and rumination [43, 44, 45]. Suppression involves the inhibition of both emotional expression and thoughts. According to Gross’s model [44, 46, 47], this is a response-focused strategy that restrains emotional expression and temporarily reduces the subjective experience of emotion, but it is ineffective in regulating emotions and physiological arousal over time. In addition, the suppression of unwanted thoughts may paradoxically lead to increased access to these suppressed thoughts [47], resulting in heightened emotional arousal, particularly in the physiological domain, which is considered maladaptive [48]. Rumination is the repetitive focus on the emotional experience, its causes and effects [48, 49]. This strategy is used to further understand and solve problems [50]. However, it can inhibit positive problem-solving [51] and lead to indecision and difficulty in taking action [52].

The benefits of using adaptive ER strategies at an early age are well documented. For example, a systematic review and meta-analysis examined 150 empirical studies on ER abilities (using teacher-, parent-report and task-based assessments) in early childhood and their association with various outcomes [18]. The authors reported that these abilities, assessed around the age of 4, predicted 25 developmental outcomes. Particularly, ER was positively associated with social competence, school engagement and academic performance and negatively associated with internalising problems (e.g. depressive symptoms), peer victimisation and externalising problems (e.g. aggressive behaviour) in early school years (around age 8), later school years (around age 13) and adulthood (around age 38). Other empirical research has shown that ER in pre-schoolers is positively related to social and school engagement (i.e. appropriate interactions with adults, peers and/or materials) and prosociality and negatively related to hyperactivity [53].

The consequences of using suppression or rumination strategies in early childhood are less studied, probably due to the linguistic and cognitive limitations of this age. However, some research has addressed this matter. For example, a study employing a puppet procedure investigated 3- and 4-year-old children’s views about ‘effective’ (e.g. cognitive distraction) and ‘ineffective’ (e.g. rumination and venting) ways of controlling anger, sadness and fear [42]. Compared to adults, children reported that “ineffective” strategies, such as rumination, resulted in greater reductions in negative emotions. The authors suggest that this may be because they have less understanding of or experience with emotion regulation, or because they ‘genuinely consider a strategy like rumination to be effective because they know that emotions sometimes improve with the passage of time’ (p. 11). Other evidence supports the negative impact of maladaptive ER strategies on behaviour and cognition. A study of 193 pre-schoolers aged around 55 months, using teach-report assessments, showed that those who used more maladaptive ER strategies (e.g. anger and frustration) were more likely to engage in aggressive behaviours [54]. Another study involving 119 children aged around 69 months, and using a task-based assessment (i.e. children’s directed attention and concentration to a movie clip), found that the use of suppression hinders their self-control resources [55].

In summary, evidence suggests that young children still develop their emotional awareness and regulation abilities. They often rely on strategies such as seeking comfort from caregivers. These early attempts at emotion regulation can be seen as advantageous, providing children with a sense of security and helping them to cope with overwhelming experiences. In contrast, children who use maladaptive strategies are more likely to experience difficulties in interacting with others and may be more vulnerable to developing psychopathology.

2.2 Emotion regulation as a transdiagnostic factor

Clinical psychopathology has been dominated by a disorder-specific approach to diagnosis and treatment that does not always adequately address comorbidity and symptom overlap between disorders. Furthermore, many risk factors appear to lead to different rather than specific disorders, and the same intervention strategies appear to alleviate these different conditions [56]. These limitations have been highlighted [57], and research has investigated the processes underlying different disorders. Among these, ER has received some attention, as numerous systematic reviews have demonstrated that distinct psychological disorders are related to altered ER, both in adults [43, 58, 59] and children [5]. Due to the apparent role of ER difficulties in different psychopathologies, it has been proposed that it should be considered as a transdiagnostic mechanism [56].

A transdiagnostic framework aims to conceptually understand and explain comorbidity across psychopathology [60]. In line with this, the National Institute of Mental Health (NIMH) has developed the Research Domain Criteria (RDoC) initiative, which provides a translational framework of basic domains of functioning—negative valence, positive valence, cognitive, social processes and arousal/regulatory systems—that underlie human behaviour, from typical to atypical manifestations, and reflect cognition, emotion, motivation and social behaviour processes. Accordingly, clinical conditions emerge from dysfunction in these processes, which predate diagnosis and can be measured through multiple levels of analysis—biological, physiological and behavioural [61, 62]. ER has gained notable importance in the transdiagnostic literature, which suggests that emotion regulation dysfunction not only contributes to distinct conditions (e.g. internalising disorders or conduct problems), but also is comorbid across different forms of psychopathology (see [5] for a review).

Research suggests that difficulties in ER reflect a mechanism underlying the co-occurrence of psychopathology in childhood. A recent meta-analysis of 60 longitudinal studies reported that maladaptive ER strategies (e.g. rumination), assessed using self-report and experimental (e.g., delay of gratification task) measures, are stable, long-term risk factors for developmental psychopathology in children and adolescents [63]. Consistent with this, another meta-analytic review of longitudinal evidence found that appropriate emotion regulation abilities, measured using parent-report questionnaires, at an early age were associated with later lower levels of psychopathology (internalising and externalising problems) [64]. Empirical evidence further supports these findings. Parent-report measures of emotion dysregulation (e.g., irritability) in children aged 3–5 years have been found to predict later mood and externalising disorders in late childhood and adolescence [65, 66].

Studies investigating experiences of childhood maltreatment also contribute to support the transdiagnostic role of ER in psychopathology. A large meta-analysis of 215 studies using report measures (i.e. questionnaires) documented that ER difficulties (e.g. rumination or suppression) in children who experienced maltreatment were positively associated with psychopathology in preschool children (i.e. internalising, and externalising problems) [67]. Consistent with this, a study using a multilevel modelling approach showed that childhood maltreatment was associated with lower positive effect and higher negative effect, as well as reduced success in ER, as assessed by report instruments [68]. A longitudinal study found that childhood maltreatment was associated with increased emotional reactivity, measured using a task-based experiment (i.e. a visual dot-probe task using affective faces), and the use of suppression and rumination strategies, measured using self-report questionnaires, which mediated the association between maltreatment and psychopathology over time [69].

Further support for the role of ER as a transdiagnostic process comes from studies of children with neurodevelopmental disorders, such as autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) [70]. ASD and ADHD preschool children tend to show marked difficulties in ER, either in parent-report questionnaires or in observational tasks (e.g. frustration-elicited task) [71]. In ASD, ER difficulties have been proposed as a core feature of this condition [72], as it is a strong predictor of symptom severity [73]. Autistic pre-schoolers, compared to typically developing children using observational methods (e.g. free play in an unstructured setting), often show less appropriate ER strategies (e.g. seeking social support) and more maladaptive strategies (e.g. avoidance), as well as increased difficulties in regulating impulsivity to emotional events and more negative effect [74]. Similarly, impulsivity in ADHD children may be related to ER difficulties. For example, a meta-analysis focusing on young children with ADHD has shown that these children have increased difficulties in emotion recognition and exhibit greater emotional lability (i.e. increased shifting of emotions, intense emotional responses), as evidenced by greater behavioural negative emotionality (e.g. anger, frustration) during frustration/challenging tasks [75].

Overall, the evidence points to the importance of adequate ER abilities at an early age and how ER dysfunction may act as a risk factor for the development and maintenance of psychopathology. Promoting effective ER abilities in early childhood not only contributes to enhanced cognitive, behavioural and interpersonal functioning but also serves as an important protective factor against various mental health problems later in life.

3. Neurophysiological correlates of emotion regulation

Emotional functioning develops rapidly in early childhood supported by several neurophysiological mechanisms and structures that mediate the dynamic interplay between emotion, cognition and behaviour. Although less investigated than in adults, a few studies have explored the neural and physiological correlates of ER at early ages.

Neuroimaging research highlights the role of the amygdala and prefrontal cortex (PFC) in ER throughout childhood. For example, a positive association between functional connectivity of the right amygdala-medial prefrontal cortex (mPFC) and parent-reported emotion regulation scores was found in children aged 4–6 years [76]. In addition, right amygdala-mPFC connectivity was negatively correlated with right amygdala reactivity to facial emotional expressions and parental reports of child negative effect. This finding is consistent with previous research in older children, adolescent and adults, suggesting that the amygdala and mPFC are key neural substrates for emotion processing and regulation across the lifespan [77].

The amygdala has been implicated in emotional reactivity and processing of the stimuli affective arousal and salience [78, 79, 80, 81]. Regions of the PFC, in turn, have been implicated in working memory, inhibitory control, attention and planning [82] processes that are essential for generating and maintaining adaptive ER strategies [80]. In addition, regions of the PFC are often connected to the amygdala, thus contributing to integrate information from the emotion generative and regulatory systems and promote adaptive ER abilities [83]. For example, depressed 4–6-year-old children showed increased activity in the right amygdala when viewing faces of different emotions compared to their non-depressed peers [84]. The authors also found a positive association between amygdala activity and parental reports of children’s negative effect but a negative association with their perceptions of children’s ability to successfully self-regulate their emotions. In another study of children aged 4–7, greater exposure to early life adversity (e.g. serious accident, parental conflict) was significantly associated with weaker amygdala–mPFC functional connectivity, which in turn was associated with more parent-report symptoms of aggressive behaviour and attention problems [85]. Further evidence of the role of these two brain regions derives from studies linking disrupted functioning of the amygdala and related brain circuits to emotional problems in young children with neurodevelopmental disorders. Significantly reduced connectivity between the amygdala and other brain areas important for socio-communicative behaviours (e.g. mPFC, temporal lobe) has been observed in autistic preschool children (mean age of 3.5 years) compared to typically developing peers [86]. Furthermore, this work observed that altered functional connectivity between the amygdala and frontal lobe was associated with greater autistic symptom severity.

The involvement of the PFC has also been confirmed in previous works using functional near-infrared spectroscopy (fNIRS) to study frustration in childhood, which is particularly relevant to the regulation of emotions when a desired goal is not achieved. Increased bilateral PFC activation was observed in children aged 4–7 years in response to elicited frustration (i.e. receiving negative feedback) in social contexts, with those children who scored higher on parent-report measures of their negative affectivity showing less brain activation in this brain region [87]. Similar findings were reported in a study of 3- to 5-year-old children [88]. Greater activation in the middle PFC was observed in response to winning a prize in a computer game, whereas increased lateral PFC activation was registered in the frustration condition (i.e. losing a desired prize). Furthermore, changes (increases) in PFC activation to a frustration task were observed in children aged between 4- and 6-years following exposure to a conscious ER interpersonal scaffolding condition, in which children interacted with the examiner during a colouring activity designed to deliberately associate physiological sensations and cognitions with emotions [89]. Among children assigned to the interpersonal scaffolding condition, being rated by their parents as having better emotion regulation abilities was associated with greater increases in PFC activation.

Another neurophysiological marker associated with ER has emerged from studies using electroencephalography (EEG) and event-related potentials (ERPs). ERP frontal N2 and P3b responses were examined as indicators of ER in 4–6-year-old children [90]. The results showed a higher amplitude and shorter latency of the N2 component, as well as a larger P3b, when viewing pictures of angry (vs. happy) faces. Children described by their parents as temperamentally more fearful showed an earlier N2 response to angry faces. Frontal N2 (occurring approximately 200–400 ms after stimulus onset) and P3 (observed in adults approximately 300–500 ms after stimulus onset) components are thought to tap into inhibitory control and attentional regulation processes, as well as action and conflict monitoring, reflecting related activity in regions of the PFC, such as the anterior cingulate cortex (ACC) and orbitofrontal cortex (OFC) [91, 92].

Another ERP index that has been studied in relation to ER is the late positive potential (LPP). The LPP is indicative of attentional processing of negative emotions and emerges as a potentially relevant neural signature for dysregulation of behaviour and effect [91]. The LPP response typically increases to emotional rather than neutral stimuli, but in contrast, a decrease in the LPP response has been reported following the use of ER reappraisal strategies in adults and older children (see [91, 93] for a review). In accordance with this, emotional content (vs. neutral condition) elicited larger LPP amplitudes in children aged 4–6 years [94, 95], but findings on the effect of reappraisal have been inconsistent. One study found that directed instructions to reappraise unpleasant stimuli did not down-regulate LPP, suggesting that young children may still be developing their ability to use cognitive reappraisal strategies [94]. However, another study found that pre-schoolers registered lower LPP amplitudes following simplified instructions for neutral compared to negative interpretations [96]. These inconsistencies may be related to the nature of the reappraisal task administered to the children and thus require further investigation. On the other hand, frontal EEG activation has also been implicated in emotion processing and regulation, with left frontal asymmetry (FA) (i.e. greater activation in the left hemisphere relative to the right hemisphere) being an indicator of appropriate emotional functioning and more adaptive ER abilities [97, 98]. For example, greater left FA has been found in adults during the performance of an appraisal task involving the visualisation of negative pictures [99]. In 9- to 10-year-old children, greater left FA during cognitive appraisal of a sad video clip was observed in those whose parents also used adaptive cognitive ER strategies and when the children reported greater inhibition of negative emotions [100]. Moreover, task-related FA assessed at 4½ years of age predicted later emotional functioning—greater left FA was associated with parent reports of appropriate ER abilities at 9 years of age [101]. In 4-year-old children, patterns of greater right FA were related to parent reports of more externalising and internalising problems in sociable and shy children, respectively, compared with children who showed greater left frontal activation [102]. However, a recent meta-analysis [103], examining the relationship between self-regulation (ER, effortful control and executive function) and frontal EEG activity during infancy and early childhood (up to 6 years of age), found a significant association only between frontal EEG alpha activity and executive function, but not with ER. Despite the substantial evidence suggesting that EEG frontal asymmetry is a potentially relevant marker of later maladaptive emotional functioning, future research is needed.

Finally, respiratory sinus arrhythmia (RSA)—computed by measuring the heart rate pattern taking into account the frequency of respiration—is a particularly important neurophysiological mechanism for the development of ER abilities and vulnerability to several forms of psychopathology [104]. RSA reflects the action of the vagus nerve supporting the link between the individual’s physiological functioning and social behaviour [105]. Greater RSA at baseline and RSA withdrawal (i.e. a decrease in RSA during challenging conditions) have been associated with better regulatory abilities and more positive developmental outcomes [106, 107, 108]. Studies show that RSA was associated with the ability of 5- to 6-month-old infants to recover and self-soothe during a Face-to-Face Still-Face paradigm [109, 110]. In addition, 10-month-old infants’ higher vagal withdrawal during an arm restraint procedure was associated with more observed maternal orienting (e.g. looking), but not distracting, regulatory behaviours [111]. RSA also discriminated physiologically between infants (6 months) classified as more or less easily frustrated, as measured by maternal reports of their temperament, and observed behaviour during a task-based experiment (i.e. frustration-elicited task), such that more easily frustrated infants displayed greater RSA and had problems with RSA withdrawal in response to an attention-demanding task [112]. Another study showed that lower RSA recovery (i.e. an index of ER) during a fear-provoking situation at 42 months of age was associated with higher parent reports of externalising problems at 48 months [113]. Children aged 2–5 years who showed higher RSA during a challenging social interaction (i.e. playing with unfamiliar peers) exhibited fewer internalising and externalising problems and better self-regulatory behaviours assessed 6–10 months later [114]. There is also evidence indicating that children’s ability to physiologically regulate themselves is related to parental behaviours and psychopathology (e.g. depression) [113, 114].

In conclusion, neuropsychophysiological research seems to indicate that specific markers may underlie adaptive and maladaptive ER. However, longitudinal studies and multi-method approaches are needed, especially when assessing young children. In this way, the developmental changes in emotion processing and regulation that occur during childhood and the acquisition of related skills (e.g. attention, inhibitory control) can be examined to gain a more comprehensive understanding of ER abilities.

4. Conclusion and future directions

The aim of this chapter was to highlight and discuss the importance of supporting appropriate ER abilities in early childhood. Appropriate emotion regulation strategies at an early age are likely to contribute to higher levels of emotional intelligence, as children can effectively manage, understand and deal with their own emotions [9]. Promoting emotion regulation abilities in early childhood may then lay an important foundation for increased emotional intelligence, fostering emotion recognition and contributing to improved interpersonal relationships and social interactions.

In this chapter, we have presented how the current literature supports the development of adjusted ER abilities in young children. Adaptive ER strategies are associated with long-term cognitive, social and mental health outcomes and have a significant impact on children’s successful development. Furthermore, we have examined current evidence on the role of neuropsychophysiological markers associated with ER abilities and how specific physiological responses underlie adaptive and/or maladaptive strategies. In summary, the literature suggests that promoting and supporting the development of appropriate ER abilities, both behavioural and physiological, in early childhood will enable children to be emotionally competent, deal effectively with personal and interpersonal difficulties as well as work with others in social settings, to the benefit of children, families, educators and society.

However, it is important to recognise that the optimal development of ER abilities occurs in an interpersonal context. Although this topic was not the aim of this chapter, it is important to consider that ER emerges in the socialisation process and that the parent/caregiver-child relationship is crucial at an early age for their optimal regulation. Therefore, future studies should address the dyadic context in the emergence and development of ER. For example, examine how parenting styles (e.g. permissive, or authoritative), or the role of intergenerational transmission, affect the development of ER abilities (e.g. whether children tend to adopt similar strategies as their caregivers/parents). Similarly, future studies should investigate how peer interactions (e.g. friendships and social support networks, e.g. school setting) influence emotion management and regulation in young children. It is also important to investigate how cultural factors may influence the development and effectiveness of ER strategies from an early age, as evidence in adults suggests that culture may lead individuals to regulate their emotions differently [115]. In the same line, future neurophysiological studies should consider the contributions of interbrain synchrony (i.e. spatial and/or temporal coordination of biological and behavioural systems between individuals, [116])—particularly in the context of parent/caregiver-child interaction—to the development of appropriate ER abilities.

Finally, as we live in the digital age, it is increasingly important to examine the impact of technology on ER. At an increasingly young age, children are often exposed to and interact with others through digital devices and social media. Future research should investigate how digital communication and social media may affect the development of ER and EI and whether it differs from face-to-face interactions.

Acknowledgments

This work is funded by national funds through the FCT—The Portuguese Foundation for Science and Technology, I.P., under the Project UIDB/04375/2020.

Conflict of interest

The authors declare no conflict of interest.