Maturity (psychological) - Biological and Evolutionary Markers

Biological and Evolutionary Markers

Where maturity is an earned status that often carries responsibilities, immaturity is then defined in contrast by the absence of serious responsibility and in its place is the freedom for unmitigated growth. This period of growth is particularly important for humans, who undergo a unique four-stage pattern of development (infancy, childhood, juvenility, adolescence) that has been theorized to confer a number of evolutionarily competitive benefits (Locke & Bogin, 2006). In infancy, motor development stretches long into the early years of life, necessitating that young infants rely on their mothers almost entirely. This state of helplessness provides for an intensely close bond between infant and mother, where separation is infrequent and babies are rarely out of a caregiver’s arms. For non-human primates and all non-human mammalian species the growth of the first permanent molar marks the end of lactation and the beginning of foraging, setting an early requirement for independence. Human children, on the other hand, do not have an advanced motor control capable of foraging and also lack the digestive capacity for unprepared food, and so have always relied on the active involvement of their mother and other caregivers in their care into childhood.

The pre-frontal cortex, which is responsible for higher cognitive functions such as planning, decision-making, judgment and reasoning, develops and matures most rapidly during early adolescence and into the early 20s. Accompanying the growth of the pre-frontal cortex is continued synaptic pruning (the trimming of rarely used synapses) as well as an increased myelination of nerve fibers in the brain, which serve to insulate and speed up signal transmission between neurons. The incomplete development of this process contributes to the finding that adolescents use their brain less broadly than do adults when asked to inhibit a response and show less cross-talk (communication across diverse regions of the brain). The brain’s “cross-talk” may be related to decision-making concerning risk-taking, with one study of American adolescents finding delayed reaction time and decreased spread across brain regions in a task asking them to determine whether a dangerous action is a good idea or not. Steinberg observes that there is close overlap in the activated brain regions for socioemotional and reward information, which may pose a challenge when making decisions in the most high-risk peer contexts. One study found that preference for small immediate rewards over larger long-term rewards was associated with increased activation with regions primarily responsible for socioemotional decision-making.