As previously defined (section 2.5), emotion response tendencies are comprised of distinct aspects of experiential, behavioural and physiological response patterns. Measuring only one or two of these channels yields an incomplete picture of emotion and its regulation that can be enhanced by the contribution of micro-physiological processes that accompany emotion regulation behaviours. William James (1884) originally proposed that subjective emotional feelings are derived from the bodily consequences of the perception of events that have some innate or acquired relevance to survival. Over the past two decades, psychologists have applied a range of physiological techniques to understanding the functions of the brain and its nervous system. Ample research demonstrates how emotions affect physiological factors such as body temperature, heart rate, blood pressure and gut motility (Critchley, 2002). Until the advent of functional neuroimaging, psychophysiological techniques, such as skin conductance measurement, were considered the primary means for inferring the neural processes underlying emotion, attention and learning (Navqi & Bechara, 2006). Electrodermal activity (EDA) as indexed by skin conductance level (SCL) is influenced by increases and decreases in hydration of the eccrine sweat glands (Beijersbergen et al., 2008). Such physiological responses provide an index of the autonomic nervous system (Porges, 1995). Illustrated in Figure 2.3, the ANS consists of two subsystems: the parasympathetic nervous system (PNS) and the sympathetic nervous system (SNS). EDA is directly controlled by the SNS (Dawson, Schell, & Filion, 2007) and in situations in which emotions are elicited, measures of EDA have been used to gain insight into the activity of the ANS (Bradley & Lang, 2000b). ANS activity has been recorded in a range of studies measuring negative emotions (e.g. anger, anxiety, disgust, embarrassment, fear
and sadness) and positive emotions (e.g. amusement, contentment and happiness; Kreibig, 2010). Reactivity, in the context of emotion, refers to the individual differences in emotional responsiveness to eliciting stimuli (Mullin & Hinshaw, 2007). In situations laden with emotional challenge, EDA activity can provide a window on emotions that may or may not be overtly expressed (Beijersbergen et al., 2008). In a range of studies, EDA reactivity has been shown to be a sensitive marker of aversion to, or avoidance of affective stimuli or cues such as punishment (Fowles, Kochanska, & Murray, 2000) in the context of family stress, including marital conflict (El-Sheikh, 2005), parental depression (Cummings, Davies, & Campbell, 2002) and paternal antisocial behaviour (Shannon, Beauchaine, Brenner, Neuhaus, & Gatzke-Kopp, 2007).
Figure 2.3: Organisation of the Autonomic Nervous System showing sympathetic and parasympathetic branches
Physiological over or under responsiveness to an emotional event may signal risk for the development of psychopathology (Cole, Zahn-Waxler, Fox, Usher, & Welsh, 1996). In studies with young people, sympathetic reactivity is associated with distress under conditions of threat and much research has focused on negative emotion associated with conduct problems and criminal behaviour (e.g. Herpertz et al., 2001). In studies of children and adolescents, EDA hypo-reactivity (low skin
conductance levels) is found to be a robust correlate with the antisocial and aggressive behaviours (e.g. Posthumus, Böcker, Raaijmakers, Van Engeland, & Matthys, 2009) associated with conduct disorder. Under-reactive individuals are believed to experience low fearfulness and disinhibited behaviour and are conceptualised as failing to learn avoidance and insensitive to punishment (Raine, 2002).
In contrast, EDA hyper-reactivity, as measured by a higher general arousal of skin conductance, is believed to denote increased sympathetic activation as a result of a) sensitivity to negative emotions, b) a desire to avoid negative consequences and c) the additional demand of suppressing emotionally expressive behaviour (Blair, 2003). High skin conductance levels are also associated with individuals who demonstrate reactive aggression (though not proactive aggression; Hubbard et al., 2002) and who are fearful and anxious (Weems, Zakem, Costa, Cannon, & Watts, 2005). In some studies, greater EDA reactivity is found to predict classroom-appropriate behaviour, particularly in children who are sensitive to punishment and prefer to avoid this consequence (Blair, 2003). Somewhat dichotomous are findings of physiological hyper-reactivity in children rated as less on task in the classroom. For these children, it is suggested that they may disengage from persisting at a task when overwhelmed physiologically from the demands of controlling their attention and inhibiting distractions (Eisenberg et al., 2005).
Recent work has begun to consider the interaction effects between hypo- and hyper-reactivity of sympathetic activation and the environment in which children are raised. In much the same way as genetic studies have begun to do (e.g. Caspi et al., 2002), current research enquiry is interested in whether SNS reactivity tendencies can provide a biological marker for later psychopathology. From a child development perspective, differential susceptibility suggests that some people are more vulnerable than others to the negative effects of early adversity but also may be disproportionately susceptible to the beneficial effects of supportive and enriching (or just the absence of adversity) environments (Belsky & Pluess, 2009). Kochanska, Brock, Chen, Aksan, and Anderson (2015) explored the idea of differential susceptibility in children with low and high skin
conductance levels. They found that positive and negative variations in parental responsiveness moderated the later emergence of externalising problems in children with hypo-reactive EDA. Whilst it seems that hyper-reactive children are predicted to be sensitive to the behavioural interactions of their environment the evidence for differential susceptibility in respect of EDA has yet to be established. As the emphasis on the interplay between children’s early experiences and biological individuality increases, it seems likely that future research will consider plasticity in relation to the autonomic nervous system and measures of electrodermal activity. These will no doubt have an impact on understanding emotion regulation in both clinical and community samples.
As has been discussed, there is still some uncertainty in the literature as to how physiological processes relate to the internalising and externalising behavioural patterns on display in the classroom. Evidently, a range of individual differences in experience, behaviour and physiology of emotion regulation exists.