Middle Childhood: An Evolutionary-Developmental Synthesis

Middle childhood is a crucial phase of human development characterized by a global shift in cognition, motivation, and social behavior. In this article, I review recent work on middle childhood from an evolutionarydevelopmental perspective and show how contributions from a range of disciplines can be synthesized into an integrated model of this life stage. I begin by reviewing the main evolved functions of middle childhood and the underlying hormonal mechanism of adrenarche. Then, I introduce the idea that the transition to middle childhood works as a switch point in the development of life history strategies. Finally, I discuss three insights into the nature of middle childhood that arise from an integrated approach. KEYWORDS—adrenarche; evolution; middle childhood Middle childhood—conventionally from about 6 to 11 years—is a crucial yet underappreciated phase of human development. On the surface, middle childhood may appear like a slow-motion interlude between the transformations of infancy and early childhood and those of adolescence. In reality, this life stage is anything but static: The transition from early to middle childhood heralds a global shift in cognition, motivation, and social behavior, with profound and wide-ranging implications for the development of personality, sex differences, and even psychopathology (see Table 1). In the last two decades, converging theories and findings from anthropology, primatology, evolutionary psychology, endocrinology, and behavior genetics have revolutionized our understanding of middle childhood. In this article, I show how these diverse contributions can be synthesized into an integrated evolutionary-developmental model of middle childhood. I begin by reviewing the main evolved functions of middle childhood and the cognitive, behavioral, and hormonal processes that characterize this life stage. Then, I introduce the idea that the transition to middle childhood works as a switch point in the development of life history strategies (Del Giudice, Angeleri, & Manera, 2009, 2012; Del Giudice & Belsky, 2011). Finally, I discuss three insights into the nature of middle childhood that arise from an integrated approach. WHAT IS MIDDLE CHILDHOOD? Middle childhood is one of the main stages of human development, marked by the eruption of the first permanent molars around 6 years and androgen secretion by the adrenal glands at about 6–8 years (Bogin, 1997). In middle childhood, body growth slows considerably, usually following a small mid-growth spurt. At the same time, muscularity increases and the body starts accumulating fat (the adiposity rebound; Hochberg, 2008), while sex differences in body composition become more pronounced (Del Giudice et al., 2009; Wells, 2007). Figure 1 places middle childhood in the broader context of human growth from conception to adolescence. In biological terms, middle childhood corresponds to human juvenility—a stage in which the individual is still sexually immature but no longer depends on parents for survival. In social mammals and primates, juvenility is a phase of intense learning—often accomplished through play—in which youngsters practice adult behavioral patterns and acquire social and foraging skills. Indeed, the duration of juvenility in primates correlates strongly with the size and complexity of social groups, as well as with cortical brain volume (Joffe, 1997). Social learning in juvenility can be understood as investment in embodied Marco Del Giudice, Department of Psychology, University of New Mexico. Correspondence concerning this article should be addressed to Marco Del Giudice, Department of Psychology, University of New Mexico, Logan Hall, 2001 Redondo Dr. NE, Albuquerque, NM 87131; e-mail: [email protected].