An important and enduring question for communication science concerns why people interact in the ways they do. This issue has been simplistically framed as a “nature– nurture” question although the process is substantially more complex than can be captured by a dichotomous metric. Until the early 1970s, genetic inheritaance played a central role in accounts of psychological development. Critics, however, argued that the correlations in the 0.50 region between identical twins’ personality scores indicated that no more than 25 percent of the variance in personality was attributable to genetic inheritance.
This observation prompted a host of behavioral theories positing features of the social environment as the primary shapers of behavioral patterns and personality. Of these models, Bandura’s (1971) social learning theory emerged as most prominent. According to Bandura, people imitate (model) another’s behavior, depending on patterns of reinforcement and punishment vicariously witnessed in response to the model’s action. Whether an action pattern is repeated by the observer also depends on the reinforcement contingencies associated with the observer’s enactment of the model’s behavior. Beatty and associates have proposed that individual differences in communication behavior and responses to messages are manifestations of individual differences in inborn thresholds for activation of the neurobiological systems responsible for the particular response.
In the late 1990s, Beatty and McCroskey began re-examining the relative roles of inheritance and social environment on the etiology of emotion-based communication traits such as verbal aggressiveness (Beatty & McCroskey 1997) and communication apprehension (Beatty et al. 1998). Beatty and McCroskey’s work was informed by the massive research literature that had accumulated under the rubrics of psychobiology, temperament, and cognitive-neuroscience (for references see Beatty et al. 1998, 2001b).
In spite of the general dominance of learning theory accounts of behavior and personality evolution, the role of genetic inheritance re-emerged in these literatures. Beatty and McCroskey took note of two insights about the earlier criticisms of twins studies. First, while it was true that the correlations were in the moderate range, it was also true that the reliability coefficients for the measures employed rarely exceeded the observed correlations by much. Given that the correlation between two variables cannot exceed the square root of the products of their reliabilities, it was possible that much of the unexplained variance in twins studies was due to measurement error rather than a substantive factor. Second, when correlations between variables are spurious in nature (i.e., the variables are correlated because of a common latent factor), which is the case with correlations between twins’ scores (i.e., personality scores are assumed to represent underlying genetic profiles, which are common to both twins), the correlation, not its square, represents the best estimate of shared variance (for explications, see Jensen 1971; Ozer 1985; D’Andrade & Dart 1990; Beatty 2002). Like many other researchers, Beatty and McCroskey viewed these psychometric oversights by critics as reason to question whether genetic explanations were prematurely abandoned. In addition, Beatty and McCroskey were heavily influenced by the temperamentand psychobiology-oriented theorists who posited several intervening variables between genetic inheritance and behavior. In such models, contemporary approaches depict genetic inheritance as having indirect rather than direct effects on behavior.
With respect to communicator traits, Beatty and McCroskey hypothesized that traits represented thresholds of activation of specific neurobiological systems. Because their initial work was limited to traits, which at the conceptual level contained a strong emotional component, Beatty and McCroskey anchored their work in Gray’s (1991) neurobiological model of emotion. According to Gray, one set of neurological circuits – termed the fight or flight system (FFS) – consists of the basolateral and centromedial nuclei of the amygdala, the ventromedial nucleus of the hypothalamus, the central gray region of the midbrain, and the somatic and motor nuclei of the lower brainstem. Painful or frustrating input stimulates the system components, which combine to coordinate the brainstem effectors in producing defensive and aggressive behavior. Cessation of behavior results from stimulation of the behavioral inhibition system (BIS), which consists of the hippocampus, the subiculum, the septum, and the limbic system. The BIS is activated by novel stimuli and those associated with potential punishment or cessation of reward. The behavioral activation system (BAS) describes the neurobiological system that energizes goal-directed behavior. Anatomically, the BAS consists of the basal nuclei, the neocortical regions connected to it, the dopaminergic fibers that extend from the midbrain, and the thalamic nuclei. Although the anatomical regions and interconnections described by Gray are common across humans, there is considerable variance in the population regarding thresholds for triggering the systems and the intensity of response once activated. Gray referred to these individual differences as “parameter values” and argued, “the major dimensions of personality . . . are created by individual differences in such parameter values” (Gray 1991, 23). By major dimensions of personality, Gray meant psychoticism, extraversion, and neuroticism. Strelau (1994) explicated the nature of the parameter values by pointing out that they may represent “sensitivity to neurons’ postsynaptic receptors or sensitivity in their synaptic transmission, the amount of neurotransmitter being released, or the reactivity of the neural structures (including receptors) to the different kinds of stimuli” (Strelau 1994, 135).
Zuckerman (1994) reviewed a huge body of research that demonstrated that biochemical signatures detected in the analysis of body fluids were accurate post-reaction indicators of particular neurobiological activity and that biochemical markers differentiated individuals along the dimensions of personality. Because the biochemical analyses supported Gray’s contention that the BIS, BAS, and FFS were the neurobiological underpinnings of neuroticism (N), extraversion (E), and psychoticism (P), Beatty and McCroskey viewed measures of N, E, and P as efficient proxy indices for the three emotional systems described by Gray. In their initial work, Beatty et al. (1998) reviewed literature that indicated that the neurobiological conditions for trait communication apprehension were a low threshold for BIS activation and a high threshold for BAS activation. Accordingly, they hypothesized that communication apprehension scores would be positively correlated with neuroticism but negatively correlated with extraversion. Both hypotheses were confirmed. Similarly, Valencic et al. (1998) found general support for a model of trait-like verbal aggressiveness using measures of E, N, and P.
Heritability Of Communicator Traits
The scholarly dialogue concerning the origin and development of communicator traits centers around two predictor variables: social environment and genetic inheritance. With respect to environment, Beatty and McCroskey differentiate physical influences (e.g., chemicals) from social features (e.g., situations). Theoretical statements regarding “environment” are limited to social features in their work. Observation that malnutrition during childhood affects brain development, for example, is not inconsistent with Beatty and McCroskey’s position on trait development.
Although the substance of the etiological literature would seem to imply that traits are either due to genetic inheritance, social environment, or some combination of the two, such a view assumes only possible direct effects models. Beatty and McCroskey proposed an indirect effects model in which genetic inheritance is the principal (but not only) contributor to neurobiological operational parameters, which in turn are the primary (but not only) influences of traits. The variance in traits due to genetic inheritance, therefore, should be equal to the product of the coefficient between genetic inheritance and neurobiological set points and the coefficient between neurobiological set points and traits. Even if the strength of association were set at 0.80 for each path, the hypothesized percent of variation in traits attributable to genetic inheritance would be 0.64. Beatty et al. (1998) suggested that inherited components of emotion-based traits such as communication apprehension could be much higher, perhaps in the 0.80 vicinity. Other traits, however, could be far less influenced by genetic inheritance.
Support for the proposition that traits are strongly influenced by the indirect effects of genetic inheritance can be gleaned from studies of infants, biochemical studies, and twins research (for references, see Beatty et al. 1998). Inheritance can be estimated from twins studies because identical twins (monozygotic) are genetically identical whereas fraternal twins (dizygotic) are no more genetically similar than non-twin siblings. Therefore, comparing correlations on variables for identical twin pairs to those of fraternal twin pairs provides a means for calculating genetic inheritance. Furthermore, partitioning twin pairs into raised-together and raised-apart cells allows analysis of common social environment effects. A massive number of studies, however, shows that the correlations are nearly identical for twin pairs raised together and those raised apart, a finding that generally holds for both identical and fraternal twins (for a review, see Zuckerman 1995).
In the communication literature, twins studies have provided interesting evidence that the biological underpinnings of many communicator traits are at least partially inherited (Horvath 1995; Beatty et al. 2001a). Beatty and colleagues (2002) meta-analyzed 40 twins studies that contained trait variables that had been cited in journal articles in communication and/or mainstream communication reference texts. This dataset provided a total sample size (i.e., n of twin pairs) of over 51,000. Conservative data analytic procedures were applied. Specifically, unless evidence of additive gene effects was absolute, nonadditive effects were assumed; unless reliability coefficients were reported in a study, the highest reliability estimate reported in the literature for a measure was employed to correct for measurement error (this decision minimized corrections); and observer ratings, although imperfect, were not corrected for attenuation. The application of these analytic procedures addressed criticisms that allege that heritability factors have been inflated in twins studies. Although the conservative procedures employed by Beatty et al. (2002) would, if anything, yield underestimates of heritability, the results indicated that 70 percent of the variation in traits related to interpersonal affiliation (e.g., extraversion, friendliness, verbal expressiveness, gregariousness, empathy, perspective-taking) was due to inheritance, 65 percent of the variance in social anxiety traits was heritable, and 58 percent of the variance in aggressiveness was heritable. Furthermore, Beatty et al. applied Plomin’s (1986) formulae for calculating variance attributable to shared and nonshared environment when analyzing twins data. The near-zero coefficients in the Beatty et al. data resulting from the application of Plomin’s formulae were consistent with Zuckerman’s (1994) observation about small effects of environment observed in the general twins literature.
Prediction Of Behavior
Although the centerpiece of Beatty and McCroskey’s work has been communicator traits, one of the major theoretical payoffs of a scientific model of communication is the accurate prediction of behavior. Theorists interested in human interaction became disenchanted with trait approaches, in part because syntheses of research appeared to indicate that correlations between traits and behaviors were quite low. Mischel (1968), for example, observed that the average correlation between traits and behavior was a meager 0.30. Beatty et al. (2001b), however, suggested that many of the problems that plagued twins research were also present in trait–behavior studies. Specifically, correcting the correlations for attenuation due to measurement error in trait measures, utilizing multiple traits to predict behavior because particular behaviors are complex and represent influences from multiple dimensions of personality, and improving the measurement of behavioral variables would all produce larger trait–behavior correlations. Beatty (2002) added that the correlation coefficient, not its square, represents shared variation if behavior is conceptualized as a manifestation of traits.
Although considerable work is still needed, two studies conducted by Beatty and his colleagues are informative regarding the speculation of Beatty et al. (2001b) about trait– behavior relationships. Heisel et al. (2003) accounted for 55 percent of the variation in observer ratings of another’s affinity-seeking competence and 58 percent of the variation in another’s verbal aggressiveness using path analysis in which multiple indicators of personality (extraversion, neuroticism, and psychoticism) were purified through confirmatory factor analysis (CFA) and employed as predictors, and observer ratings were also refined through CFA. La France et al. (2004) meta-analyzed the nonverbal behavioral correlates of extraversion studies and found negative relationships between effect size and both number of nonverbal behaviors coded and sample size, such that the largest correlations were observed in studies of a moderate number of participants and in which no more than three nonverbal behaviors were coded. La France et al. speculated that the near zero size effects for large sample, multiple variable studies were due to “coder fatigue.” Taken together, the results of these studies suggest that the prospects for accurate prediction of behavior are enhanced when complex rather than simple models are tested, and when fundamental psychometric practices are followed.
Role Of Social Environment
The role ascribed to social environment in the communibiological paradigm is complex and perhaps the most often misinterpreted aspect of Beatty and McCroskey’s work. According to Beatty and McCroskey, social environment functions differently in shaping traits than in shaping specific behavioral reactions. As already discussed, social environment is portrayed as having very little, if any, impact on the development of traits and predispositions. With respect to behavioral action, Beatty and McCroskey have proposed that situations have a negligible direct effect. Attentiveness to the statistical meaning of “direct” is essential to understanding Beatty and McCroskey’s position. Drawing from a rather large body of research indicating that (1) individuals position themselves in circumstances that are compatible with their personalities, (2) manifestations of individuals’ temperaments contribute to situations, and (3) interpretations of situations are driven by personality (for references, see Beatty et al. 2001b, 39), Beatty and his colleagues treat situational variables as endogenous rather than exogenous variables in causal models. Thus, various selectivity processes combined with individuals contributing to the fabric of situations through their own behavior are critical aspects of immediate social environments. Beatty et al. (2001b) argue that inattentiveness to individual differences in temperament is responsible for the small effect sizes observed for situational factors in experimental research. In summary, Beatty and associates hold that the objective qualities of social environment have little impact on any dimension of communicative functioning. Rather, the communicator’s subjective reaction – which is driven by temperamental traits – is associated with behavior.
Cortical Function And Cognitive Processes
Although Beatty and McCroskey have modified the basic propositions of communibiology, a consistent tenet has been that theory regarding cognitive and affective processes involved in communicative functioning must be consistent with knowledge regarding brain functioning. One strategy evident in the most recent work of Beatty and associates has been to test hypotheses that are informed by cognitive neuroscience research. For example, brain wave recordings are consistent with cognitivist positions on social interactions (e.g., Beatty & Heisel, 2007).
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