The benefits of youth

 

Authors: David F. Bjorklund ^a; Virginia Periss ^a; Kayla Causey ^a

Affiliation:
^a Florida Atlantic University, Boca Raton, Florida, USA

DOI: 10.1080/17405620802602334

Publication Frequency: 6 issues per year

Published in: European Journal of Developmental Psychology, Volume 6, Issue 1 January 2009 , pages 120 – 137

Ver TEXTO COMPLETO

Abstract

We examine human psychological development from an evolutionary perspective and propose that some aspects of developmental immaturity have been selected for their adaptive value either for individuals at a specific time in development (ontogenetic adaptations) or as preparation for adulthood (deferred adaptations). We review research and theory on the possible adaptive role of immaturity in human development, focusing on play, neural plasticity, and cognitive limitations that may foster the development of sensory systems, learning/education, and caretaking by adults. We argue that considering the possible adaptive features of immaturity, along with the obvious maladaptive ones, provides a more accurate picture of ontogeny and ways to foster healthy psychological development.

Keywords: Cognitive immaturity; Evolutionary development; Ontogenetic adaptation

As the title suggests, our thesis focuses on the benefits of youth, or more generally, on the adaptive nature of immaturity. We view development as more than a “means-to-an-end” process that produces mature adults: While each stage in development, from infancy through childhood and on to adolescence, serves a unique purpose in preparing children for adulthood, these stages also function to adapt children to their immediate environment, or developmental “niche.” This perspective is explicitly informed by evolutionary theory, and before delving into the “benefits of youth,” we examine some of the assumptions of an evolutionary approach to human psychological development.

Evolutionary Developmental Psychology

From the perspective of evolutionary developmental psychology (e.g., Bjorklund & Hernndez-Blasi, 2005; Bjorklund & Pellegrini, 2000, 2002; Burgess & McDonald, 2005; Ellis & Bjorklund, 2005; Geary & Bjorklund, 2000), natural selection operates at all stages of development, not just adulthood. Moreover, natural selection has not acted equally on all stages. To pass on their genes, individuals must survive birth, develop to sexual maturity, find a mate with which to reproduce, and successfully raise offspring to reproductive age. Therefore, selection will have its greatest effects on the early stages of ontogeny, and any benefits that encourage development through these stages will be favored, even if they are harmful later in life. For example, the very sex hormones that promote reproduction in Pacific salmon lead to their rapid post-reproductive death. In fact, if a salmon’s gonads are removed it can no longer reproduce, of course, but lives a much longer life (Robertson, 1961). In humans, there is some evidence that testosterone provides early benefits for males associated with social status and dominance, yet may suppress the immune system and increase risks of cancer and heart disease later in life (see Geary, 1998). Organisms are also at greater risk of death early in life, lacking the skills necessary for independent living. This is especially true for animals with extended developmental periods such as Homo sapiens and other nonhuman primates. Accordingly, mechanisms of evolutionary change focus on the developing organism more so than on the adult.

Humans’ extended youth

One characteristic of Homo sapiens is its prolonged period of immaturity. The closer a species’ common ancestor is with Homo sapiens, the longer its period of immaturity: approximately 2 years in lemurs, 4 years in macaques, and 8 years in chimpanzees, compared to approximately 15 years in humans (Poirier & Smith, 1974). According to anthropologist Barry Bogin (1999, 2003), humans’ extended period of immaturity was afforded, in part, by the invention of two new life stages: childhood, approximating the 3 to 7 years between infancy and the juvenile period, and adolescence, a brief 2 to 3 years following menarche, each characterized by distinct physical and psychological characteristics.

All mammal infants are dependent on their parents, especially their mothers, for care, but childhood, in particular, extends the period of high parental investment required to survive. Children cannot acquire or prepare food themselves (they still have their primary, or “baby teeth,” and many foods have to be prepared specially for them), and their physical skills are greatly limited. Moreover, although children display representational (symbolic) thought at this time, they are still largely egocentric (have difficulty considering a perspective other than their own) and demonstrate illogical thinking, which Piaget (1983) described as preoperational (i.e., lacking the logical operations characteristic of children in the juvenile, or concrete operational, period).

This extended period of dependency and delayed sexual maturation can be very costly. Caring for dependent children limits the number of offspring a woman can have, and being dependent on others for many years has its own drawbacks, including susceptibility to predation, starvation, and disease, to name a few. Moreover, the longer one delays sexual maturity, the greater the chance that one will die before reproducing. In biology, when there are great costs to a feature there must also be great benefits, otherwise the feature would have been eliminated by natural selection. The benefits of high quality, lengthy investments in slow-developing offspring must have been substantial enough to outweigh the costs. Otherwise a prolonged period of ontogeny would have been selected out of our species’ history (e.g., Bjorklund & Bering, 2003; Bjorklund & Pellegrini, 2000, 2002).

Adaptations of infancy and childhood

Understanding the evolutionary function, or benefits, of prolonged development can help us know how and why our psychology develops the way that it does. One proposed function is that this extended period of immaturity is associated with a high degree of plasticity and allows children the time and flexibility necessary to master complex skills, such as those needed for tool use, hunting/foraging, and social learning/cognition (e.g., Bjorklund, Cormier, & Rosenberg, 2005). But, we argue, it is not just time that prolonged youth affords, but an approach toward life that is unique to childhood and that may be crucial in the development of “humanness.”

Those aspects of childhood that serve as preparations for adulthood and were selected over the course of evolution are referred to as deferred adaptations (Bjorklund & Hernndez-Blasi, 2005; Hernndez-Blasi & Bjorklund, 2003). However, some aspects of infancy and childhood are not specific preparations for adulthood. Rather, they are designed by natural selection to adapt the child to its current environment, not necessarily to a future one, and are referred to as ontogenetic adaptations (Bjorklund, 1997; Oppenheim, 1981). From this perspective, aspects of children’s immature functioning are adaptive in their own right, providing infants and children with immediate (and albeit sometimes deferred) benefits.

This is, admittedly, a counterintuitive view, especially among developmentalists. Immature behavior and thought are typically seen as incomplete versions of those of adults. Immaturity is something that children must overcome on their way to adulthood, where the “real show of humanity emerges” (Thomas, 1993, p. 175). We contend that this latter view is inaccurate and insufficient in describing childhood. “Immature” physical, cognitive, and behavioral features served adaptive roles in human phylogeny and continue to have an adaptive role in human ontogeny, and we can take advantage of such immaturity to foster development (Bjorklund, 1997, 2007a; Bjorklund & Green, 1992).

Our intent is not to praise immaturity: Maturity is still the goal of development and artificial prolongation of immaturity would be deleterious. However, we suggest that there may be some adaptive functions for immaturity that coexist with the maladaptive ones, at least at certain times in development. In the following sections we examine several potential benefits to immaturity including the opportunity for play, the adaptive value of neural inefficiency, the benefits of thinking you’re better than you are, and the adaptive value of looking and acting young on others. For a more extensive discussion of the adaptive value of immaturity see Bjorklund (1997, 2007a).

Benefits of Play

Play has been man’s most useful preoccupation.Frank Caplan, educational toy developer

Play is a uniquely adaptive act, not subordinate to some other adaptive act, but with a special function of its own in human experience.Johan Huizinga, Homo ludens

Play is what children do, accounting for between 10 and 40% of children’s time and energy expenditure (see Bjorklund & Pellegrini, 2002; Pellegrini, Horvat, & Huberty, 1998). Play is not limited to humans, but is observed in many other, mainly social, species. For example, juvenile apes, canids (wild dogs), dolphins, and elephants spend large proportions of their time and energy engaging in some forms of play (e.g., see Bekoff, 1997; McCowan, Marino, Vance, Walke, & Reiss, 2000). Play is spontaneous and voluntary, while at the same time engaging and effortful. It might appear “purposeless” or as an imperfect version of adult behavior, but because of its high costs researchers have assumed that the outcomes of play must be beneficial, offering some immediate as well as deferred benefits to the developing organism (see Bjorklund & Pellegrini, 2002; Pellegrini, in press; Pellegrini & Smith,