Physiology

Another issue of interest to temperament researchers is the underlying physiological markers of individual differences in emotional reactivity. Findings from hemispheric lateralization studies are of special relevance here in understanding the links between emotion and pathology. These studies have shown differential hemispheric activation for the underlying action tendencies, such as approach and withdrawal, rather than differential activation for specific discrete emotions (Davidson, Ekman, Saron, Senulis, & Friesen, 1990; Fox & Davidson, 1987, 1988). These studies also point to important parallels between different levels of analysis—from neural activation to behavioral indices—in approaching emotion and pathology links. For example, several of the behavioral explanations Cole and Zahn-Waxler (1994) offer to account for the emotional profile of children with disruptive behavior disorders seem to be organized around action tendencies rather than specific discrete emotions. We will try to illustrate the parallels that emerge when we consider action tendencies rather than specific discrete emotions.

Both the clinical and empirical observations of children with disruptive behavior disorders show these children to be low in sadness and fear and high in anger and inappropriate joy expressions (Cole & Zahn-Waxler, 1994). Cole and Zahn-Waxler suggest that the low reactivity in sadness and fear may be a function of atypical or nonnormative coping mechanisms. This approach, therefore, clusters low reactivity in sadness and fear together through their common underlying action tendency: withdrawal. Cole and Zahn-Waxler propose that children with disruptive behavior disorders may also cope by masking sadness and fear with anger and joy, the latter two being associated with the underlying action tendency of approach. Alternatively, they propose that these children may also cope by inhibiting the expression of sadness and fear, that is, not showing any withdrawal tendencies, but rather communicating only indifference. Both of these proposals are based on behavioral observation from the clinical and empirical literature, but both emphasize action tendencies rather than discrete emotions.

As already noted, hemispheric lateralization studies with both normative and nonnormative populations show differential activation for approach and withdrawal tendencies rather than the observed discrete emotions (Davidson et al., 1990; Fox & Davidson, 1987, 1988). Most of these studies link relative left frontal activation with approach, and relative right frontal activation with withdrawal tendencies (Fox, 1994). Studies have also suggested that the dynamic balance between the two hemispheres is altered in disordered populations. For example, studies have suggested that individuals with impulsive and hyperactive

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temperaments tend to show an inhibition of withdrawal (i.e., disinhibition) through relative lower right frontal activation. In fact, individuals at risk for externalizing disorders tend to exhibit this pattern of relative lower right frontal activation. In contrast, individuals with depressed mood show relative lack of activation in the left frontal region suggesting a deficiency in approach and positive affect rather than an excess in withdrawal tendencies (Henriques & Davidson, 1990; see also Davidson, Chapter 5 of this volume). This deficiency of depressed individuals in showing approach-related behaviors converges with Zahn-Waxier et al.'s (1984) finding of deficient increases in joy reactions of toddlers with bipolar parents. Zahn-Waxler et al. found suggestive evidence that when stressful background stimulation was removed, toddlers with bipolar parents failed to show increased joy reactions in comparison to control children.

Such convergence in findings from hemispheric lateralization studies and behavioral differences found for at-risk children illustrate and emphasize the importance of indices of approach and withdrawal in emotional reactivity. More rigorous parallels at different levels of analysis are clearly important for our understanding of the relationship between emotion and psychopathology.

Direct Processes of Transmission

Also critical to questions of emotion and the development of psychopathology are studies that concentrate on the mechanisms by which parental psychopathology gives rise to nonnormative patterns in children's emotional responses. As Cummings and Davies (1994) argue in their review on the effects of maternal depression on child outcomes, a large body of research has concentrated on indirect mechanisms of influence, such as parenting and attachment. Zahn-Waxler's work has also been a part of this trend that has emphasized indirect mechanisms of influence, especially in delineating aspects of parenting practices associated with risk status (Zahn-Waxler et al., 1990). However, commentaries by Cummings (1995) and Seifer (1995) in the special section of Developmental Psychology on maternal depression, note that concentration on such indirect mechanisms is an overall limitation of the field. They suggest that this limitation is a function of our failure to generate a theoretical framework that organizes and informs our inquiry on the nature of the influence of maternal depression on developmental outcomes.

Studies conducted by Tronick (Tronick, 1989; Tronick, Als, & Brazelton, 1977; Tronick & Giannino, 1987) and Field (1984, 1994) are rare examples of efforts in the literature that have examined the direct mechanisms through which maternal depression can influence child outcomes. Most of these studies have been conducted with infants and their depressed caregivers using face-to-face interaction paradigms. These studies have shown that infant-depressed mother interactions are characterized by nonsynchronous affective expression (i.e., nonmatching affective states in valence) and an overall higher degree of negative affective exchanges compared to controls. Furthermore, experimental studies have demonstrated that similar patterns in emotional responding can be reliably elicited in infants with nondepressed caregivers, when the caregiver simulates depressed mood. However, these studies are often limited to infancy; furthermore, there are virtually no studies that examine the change or the persistence in such emotional responding beyond infancy. Neither are there any

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studies that have examined the extent to which these infants generalize non-normative patterns in emotional responding to their interactions with nondepressed adults.

Nevertheless, these findings are important to questions regarding the relations between emotion and pathology in several ways. First, because the experimental studies have utilized random assignment, their pattern of findings is not saturated by the large individual difference variation in affective styles, especially in control mother-infant dyads. Although we can certainly expect that both maternal and infant individual differences in emotionality likely account for a significant proportion of the observed variation in the frequency of positive and negative affective states, the synchronous pattern cannot solely be a function of these individual differences. Second, because infants' emotional reactions can be reliably altered with simple simulation of depressed mood by otherwise nondepressed caregivers, the findings suggest that adults' affective reactions have an asymmetrical influence in the maintenance of synchronous affective exchanges.

This asymmetry, however, does not imply that infant emotional characteristics do not influence mothers' reactions. There are numerous studies showing that difficult temperament in infancy is a correlate of maternal depression (Crockenberg & Smith, 1982). However, the interesting question this asymmetry gives rise to is how similar processes operate beyond infancy in mother-child interactions. If we were to interpret this asymmetry as contagion of mother's affective state to the infant we may speculate that such asymmetry is not likely to maintain its influence, or operate in the same fashion beyond the first year of the infant's life. The reasoning behind such a claim is that infants have limited capacity in modulating motoric approach and withdrawal reactions. However, once upward locomotion emerges there are likely to be significant opportunities for the toddler to execute withdrawal and approach reactions in multiple situations. Thus, opportunities for continued contagion of mothers' affective state are likely to be significantly altered. Perhaps, child characteristics are likely to exert stronger influences on the dyadic nature of the affective exchanges in mother-child interactions beyond the first year with their emerging motoric abilities.

Another interesting issue these findings raise is the source of this asymmetry. As already reviewed, hemispheric lateralization studies suggest that depression may be a reflection of the inability to express positive affect and execute approach behaviors, rather than an increased tendency to express negative affect and execute withdrawal behaviors. Thus, it may be that a mother's overall capacity to express approach-positive affect states is a critical element in the generation of synchronous affective exchanges. This suggests the importance of an issue raised earlier about the role individual differences in emotional reactivity may play in dyadic affective exchanges. There are no studies, however, that exemplify the extent to which individual differences in both maternal and infant emotional reactivity contribute to the variation in these dyadic exchanges. Despite the long-standing appreciation of the need to incorporate the temperamental differences that children bring to their environments (Maccoby & Martin, 1983), researchers insist on ignoring these very important sources of variation. These findings thus alert us to the heretofore largely ignored influence of maternal personality as well.

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At this juncture we must acknowledge that these rich, although ignored, sources of variation in individual differences in emotionality are also genetically based. Numerous studies have shown that a large percentage of the variation in individual differences in both infant-child (Goldsmith & Campos, 1986; Matheny, 1980; Torgersen & Kringlen, 1978) and adult emotionality (Loehlin, 1992; McGue, Bacon, & Lykken, 1993; Plomin, Chipuer, & Loehlin, 1990) is genetically influenced.

As Scarr and McCartney (1990) point out, however, the environmental variation we have discussed up to this point may be a reflection of the correlated genotypes among family members. More specifically, a child's genotype is correlated with the environment he/she is embedded in. In other words, children's genotypes are correlated with those of their parents, who in turn create and seek the environments that support those genetic tendencies. Thus, there is considerable genetic variation in “environmental measures.” For example, many studies indicate that around 50% of the variation in both infant negative affectivity (Goldsmith & Campos, 1986; Matheny, 1980; Torgersen & Kringlen, 1978) and adult neuroticism (Loehlin, 1992; McGue et al, 1993; Plomin et al., 1990) is heritable and most of the remaining variation is due to nonshared environmental influences. Thus, negative affect exchanges observed in infant-de-pressed mother dyads are likely to be largely mediated by the correlated genotypes of infant and mother. On the other hand, findings on infant positive affectivity from behavior genetic studies reveal that in addition to a heritable component, infant positive affectivity is significantly influenced by shared environmental factors (Goldsmith, Buss, & Lemery, 1997). Such shared environmental factors for positive affectivity suggest that nonsynchronous affective exchanges with a depressed mother, who has a decreased ability to execute approach and express positive affect, may be a function of concurrent depressed mood of the mother. The implication would be that infants may not generalize their responding to nondepressed caregivers. In any case, this argument shows that behavior genetic studies on trait measures of emotionality are important in teasing apart sources of influence for negative child outcomes. In other words, these studies are relevant to links between emotion and pathology because they point to sources of influence that have implications for treatment and preventive measures.

Conclusion

In this commentary we drew heavily on some of Zahn-Waxler's work with at-risk populations in addressing issues about emotion and the development of childhood psychopathology. We illustrated that her work has been central to formulations of various questions in understanding the relations between emotion and pathology. We argued that fuzzy concepts such as dysregulation need not be evoked when establishing links between normative and nonnormative patterns of emotional responding. In addition, we showed that issues of interest to temperament researchers—such as genetic and environmental origins, physiological underpinnings, stability and instability, and measurement and data-analytic techniques—can go a long way in generating explanatory power in linking emotion and psychopathology.