World Development Report 2018: Learning to Realize Education’s Promise

Research has dramatically expanded our understanding of how the brain works—and therefore how people learn. The brain is very malleable: it adapts to its surroundings. This phenomenon is called neuroplasticity, which means the ability to learn is dictated not only by genetic endowments, but also by how genes interact with experiences and environmental inputs. Genes govern when specific brain circuits are formed, but experiences can turn those genes on or off, as well as determine which neural connections—synapses— survive over the life cycle. Environmental inputs such as caregivers’ or teachers’ stimulation, or nutrition, or violence shape the architecture of the brain from the formative years on.

The brain is malleable throughout life, even if most brain development is completed by late adolescence or early adulthood. The fastest synaptic growth (thus malleability) occurs between the prenatal period and age 3 (1 million new neural connections a second), with growth then gradually slowing. Because different parts of the brain develop at different times, and because neuroplasticity is highest during developmental stages, not all areas of the brain are equally malleable at the same time (figure S1.1). The periods of greatest plasticity, or “sensitive periods,” whose length varies widely by brain region, are characterized by an initial stage in which the brain develops far more synapses than it needs. That stage is followed by synaptic pruning in which, to maximize efficiency in brain functionality, the neural connections used more often grow more permanent, while those used less are discarded to reach optimal levels of synapses (that is, the adult level of synapses in figure S1.1). Because most sensitive periods take place early in life, a 3-year-old has, in total, far more brain synapses (about 1 quadrillion) than an adult (100–500 trillion).

Although different parts of the brain have different sensitive periods, their development is interdependent. Neural circuits (series of synapses) form sequentially and cumulatively: simpler networks develop first, more complex ones later. Just as with the construction of a house, the robustness of progressively more complex brain structures depends on the robustness of foundational ones. For example, the development of increasingly complex skills and functions builds on circuits formed earlier: linguistic development relies on visual and auditory functions that are dependent on neural circuits lower in the hierarchy, which are most malleable earlier in life; neural circuits that support higher cognitive functions, most malleable until as late as adolescence, build on sensorial stimuli as well as linguistic development. Moreover, physical, sensory-motor, cognitive, and socioemotional development are interdependent, constituting a web of dynamic links that ultimately determine a person’s ability to thrive. For example, higher levels of health promote learning; emotional security fosters child exploration, which leads to learning; and higher self-regulation reduces health risks.

A range of enriching experiences leads to more complex synapses, but cumulative exposure to risk factors (such as neglect or violence) either eliminates synapses associated with healthy brain development, or it consolidates those associated with unhealthy development. Experiences affect the architecture of the brain in part because of the hormonal response they trigger. Hormones such as dopamine (triggered when the brain encounters novelty) stimulate information absorption, whereas hormones such as cortisol (associated with stress as well as negative emotions) can shut offlearning.

The available insights on brain development have

Interventions to improve learning and skills implications for investments in learning and skill should place a greater emphasis on the areas of the formation. Because brain malleability is much greater brain that are the most malleable over the life course.

earlier in life and brain development is sequential

Children’s brains are most efficient at incorporating and cumulative, establishing sound foundations can new information through exploration, play, and interlead to a virtuous cycle of skill acquisition. Moreactions with caring adults or peers. Because of this over, investment in experiences and environmental receptivity, preschool programs should concentrate inputs that foster learning at the very earliest stages on building foundational skills through developmenincreases the impact of investments at later stages:

tally appropriate program structures that emphasize skills beget skills. Weak foundations, by contrast, result play and interaction. Although foundational cogniin the accumulation of learning gaps, as well as higher tive skills become less malleable after age 10, some risks of poor biological development that hamper skill areas associated with socioemotional development formation—with repercussions over the life cycle remain highly malleable through early adulthood.

(see chapter 5). Yet the optimal periods for cultivatAccordingly, interventions that aim to improve the ing higher-order cognitive and socioemotional skills school-to-work transition, as well as social inclusion occur throughout childhood, adolescence, and early for youth with weak foundational skills, may prove adulthood. Furthermore, the brain’s ability to adapt most effective when they emphasize socioemotional to its environment, learn, and acquire new skills skills.

continues throughout life (that is, the experienceTeaching strategies can deeply influence how dependent synapse formation in figure S1.1). Thus students approach challenges in and out of school.

investments in environmental inputs are needed well

Because the brain thrives when exposed to novelty, beyond early childhood to sustain learning along with incorporating enriching opportunities for learning skills development.

along with exploration may lead to better learning outcomes. Finally, intense stress or sustained negative emotions—such as those associated with crises or acute deprivation, where multiple stressors coexist— interfere with the brain’s ability to learn, retain, and use information. Extended exposure to stressors is toxic for biological systems, particularly for developing brains, and it may impede disadvantaged children from flourishing in the classroom (see spotlight 2 on the effects of poverty). Consequently, programs that increase the availability of protective factors to shelter children from stress (such as nurturing care from at least one meaningful relationship that teaches children how to cope) can improve not only schooling, but also overall life outcomes.