On the bifurcation of temperamental shyness: Development, adaptation, and neoteny

In the present paper, the authors use Tinbergen's (1963) seminal four question framework regarding ontogeny, causation, function, and phylogeny to understand individual differences in human shyness. We argue that there are at least two shyness subtypes, an early appearing fearful shyness, and a later emerging self-conscious shyness (Buss, 1986) that develop into avoidant and conflicted shyness, respectively, in early childhood and remain relatively stable into adulthood. We proffer that each shyness subtype is presumed to have a different cause and function: fearful/avoidant shyness results from social novelty, its function is to motivate vigilance, action and avoidance of impending threat and harm from conspecifics, and is subserved by evolutionarily old brain circuits; self-conscious/conflicted shyness results from the experience of competing emotions of interest and fear of negative evaluation in social situations, its function is to allow more time for additional learning to take place about conspecifics' intentions and motives before responding, and is linked to relatively newer brain circuits. We argue for a highly speculative idea that self-conscious/conflicted shyness bifurcated from fearful/avoidant shyness later in human evolution as the neocortex grew bigger, self-awareness emerged, and the nature of social interactions became more complex. We further speculate that conflicted shyness may be reflective of neoteny (i.e., delaying maturity and retaining child-like features into adulthood). We also provide some ways in which this shyness-neoteny hypothesis can be empirically tested. We conclude by suggesting that considering the adaptive value of some temperamental phenotypes has implications for how we view normal and abnormal behavior.