The Handbook of Solitude

We sought to replicate these findings in a separate study using an independent sample of older children (age 10 to 16 years). In Study 2 (Schmidt & Poole, 2020b), we derived latent classes of observed shyness across two visits spanning approximately one year and examined if they were distinguishable on frontal ADR that was collected using EEG at enrollment. Consistent with findings in younger children (i.e., Study 1), we found that children who displayed stable‐low levels of observed shyness showed a significantly higher frontal ADR score relative to children who showed stable‐high levels of observed shyness.

In Study 3 (Schmidt & Poole, 2021), we examined the specificity of frontal ADR in relation to the positive and nonpositive shyness subtypes and a low shy group used in the Poole and Schmidt (2019b) study described above. We found preliminary evidence of a linear relation between frontal ADR score and shyness group in children, such that the positive shy group had the lowest ADR score, the low shy group the highest ADR score, and the nonpositive shy group was intermediate between the two former groups, suggesting possible differences in frontal brain maturation for some adaptive aspects of shyness.

In interpreting these findings, we have speculated two possible explanations (Schmidt & Poole, 2018, 2020b). One is a proximate explanation. That is, the pattern of less growth in the proportion of relative alpha power to delta power among shy children might reflect a neural mechanism underlying dysregulation of emotion regulatory processes in social situations, which is characteristic of some shy children. Previous work has reported that delayed frontal brain maturation may underlie some emotional and behavioral problems that are related to shyness in children (see, e.g., Dawson & Fischer, 1994; Posner & Rothbart, 2000; Schore, 1996; for reviews).

A second is an ultimate explanation. That is, delayed frontal brain maturation might reflect individual differences in the evolutionary process of neoteny. Neoteny refers to the prolongation retention of childhood characteristics and delayed maturity (Bogin, 1990; Gould, 1977, 2008). Unlike most mammals, human development is characterized by a relatively long period of childhood. This protracted period is presumed to have played a critical part of human evolution, allowing our brains to grow larger and allowing for the development of higher order cognitive processes (Bogin, 1990). Neoteny has been hypothesized as an important element to social cognitive development in humans in that one of the presumed functions of extending childhood is to allow additional time for learning to take place when the brain is highly plastic (Bjorklund, 1997, 2009; Gallese, 2017). Interestingly, there is empirical evidence for neoteny in the human brain (Somel et al., 2009), particularly the prefrontal cortex (Petanjek et al., 2011).

We have speculated that shyness may have evolved due to individual differences in frontal brain maturation, resulting from the process of neoteny (see Schmidt & Poole, 2019, for a review). The function of delayed frontal brain maturation, manifesting as an approach‐avoidance conflict in social situations, may actually allow the shy child additional time for learning of others' intentions before socially participating. Indeed, as noted earlier, expressions of positive shyness have been associated with more sophisticated Theory of Mind in two separate studies of children (Colonnesi et al., 2017; MacGowan et al., 2021). This additional time for learning others' intentions is important for negotiating familiar and unfamiliar social environments. Interestingly, perhaps the social immaturity (Rubin & Asendorpf, 1993), and delayed onset of some developmental milestones in shy children (Caspi et al., 1988) reflect the process of neoteny. We speculate that the delaying of brain maturity, particularly in the frontal brain regions, may be a neotenous feature present in some shy individuals, which serves as a putative mechanism linking shyness and adaptive behavior.

Although it is difficult to empirically test ultimate and evolutionary explanations of behavior, as reviewed in the series of EEG studies above, we have begun to explore the proximate explanation using EEG measures to index brain maturation and emotion regulatory processes underlying adaptive shyness. We have also recently begun to explore more proximate hypotheses of the adaptive nature of shyness by examining adaptive processes in the shy brain using perceptual tasks. Here we adapt shy individuals to affective faces varying in emotional expressions and examine their corresponding afterimages to that particular emotion. For example, after adapting to a positive facial expression (e.g., happy faces), the typical visual afterimage that follows is to perceive a negative facial expression (e.g., angry face), while after adapting to a negative facial expression (e.g., angry face), the typical visual afterimage that follows is to perceive a positive facial expression (e.g., happy face). However, there appear to be individual differences in the experience of these afterimages. We found that young adults who had high levels of both shyness and sociability were more likely to perceive a negative face emotion afterimage after adapting to happy faces and a positive face emotion afterimage after adapting to angry faces than young adults classified by other combinations of high and low shyness and sociability (Poole et al., 2020). These findings suggest that the experiences of these afterimages appear to be linked to personality and may be a window into understanding individual differences in how well the brain adapts to social stimuli, with some shy subtypes possibly showing an advantage in adapting to these social stimuli.

Future research could test the proposed shyness‐neoteny hypothesis in several ways (see Schmidt & Poole, 2019). First, if there are indeed maturational delays associated with some types of shyness, then perhaps these delays would be evidenced on epigenetic markers of aging, which could be examined. Second, to the extent that neoteny may have allowed for prolonged learning to take place, then there may be differences in learning and memory among some types of shyness in different social contexts that could be examined. Lastly, the shyness‐neoteny hypothesis could be tested between the sexes for preferences across a range of stimuli, for example, people expressing neotenous features (e.g., coyness, youthful smiles) and characteristics of some types of shyness could be judged for attraction and interpersonal likeability.

In this chapter, we considered the evolutionary and neuroscientific basis for shyness. More specifically, we discussed the adaptive aspects of different subtypes of shyness, the putative function of these subtypes, some of the regulatory mechanisms of shyness subtypes, and how these mechanisms maybe instantiated in the brain. We put forth a speculate hypothesis that some types of shyness may be adaptive and linked to a delaying of brain maturation (i.e., neoteny). This delaying of maturation may have served an important function in our evolutionary past as humans began to evolve, our neocortex grew larger, and social interactions became more complex in that it may have allowed some individuals more time for additional learning to take place about the intentions and motives of conspecifics. To that end, in some sense, the shy brain has remained forever young.

1 Asendorpf, J.B. (1989). Shyness as a final common pathway to two different kinds of inhibition. Journal of Personality and Social Psychology, 57, 481–492.

2 Asendorpf, J.B. (1990). The expression of shyness and embarrassment. In W.R. Crozier (Ed.), Shyness and Embarrassment: Perspectives from Social Psychology (pp. 87–118). New York: Cambridge University Press.