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factors relating to volitional control: for example, young persons have had less time to develop impulse control and to learn to resist peer pressures to offend (I label these “psychosocial factors”).177

speculation and not on empirical enquiry.180 In the early 1970s, the systematic scientific study of psychological development during adolescence began.181 Fairly recently, developmental neuroscientists have claimed that the brains of young persons are not as developed as the brains of adults. These neuroscientists thereby seem to have confirmed the longstanding popular belief that adolescence is characterized by a unique set of features that warrant its consideration as a distinct period of development.182 It appears that the brain changes characteristic of adolescence are among the most dramatic and important to occur during the human lifespan.183 Recent developmental neuroscientific research has shown that there is continued brain maturation through to the end of the adolescent period.

Findings from both cross-sectional and longitudinal imaging studies of late childhood and adolescence showed that brain regions associated with more basic functions such as motor and sensory processes mature first, followed by association areas involved in top-down control of thoughts and action. This pattern of development is paralleled by a shift from diffuse to more focal recruitment of cortical regions with learning and cognitive development. […]

The reported shift in cortical architecture and function is presumably an experience-driven maturational process that reflects fine-tuning of neural systems with experience and development.184

Steinberg describes how heightened risk taking in adolescence is the product of the interaction between two brain networks: firstly, the cognitive-control network that subserves executive functions such as planning, thinking ahead, and self-regulation and that matures gradually over the course of adolescence

180 See Elizabeth S. Scott, N. Dickon Reppucci, and Jennifer L. Woolard, “Evaluating Adolescent Decision making in Legal Contexts,” (Law and Human Behavior 1995, Vol.19, No.3: 221–44), 224ff.

181 Elizabeth S. Scott and Laurence Steinberg, Rethinking Juvenile Justice (Cambridge: Harvard University Press, 2010), 28.

182 See Sarah-Jayne Blakemore, “The social brain in adolescence,” (Nature Reviews Neuroscience 2008, Vol.9: 267–77), 267, who focuses on the development of the “social brain” that has to do with the understanding of others’ emotions, intentions, and beliefs. She reviews evidence that certain areas of the social brain undergo substantial functional and structural development during adolescence.

183 See Steinberg (2010), 160.

184 B.J. Casey et al., “Imaging the developing brain: what have we learned about cognitive development?,” (Trends in Cognitive Sciences 2005, Vol.9, No.3: 104–10), 108.

and young adulthood largely independently of puberty and, secondly, the socioemotional network that is especially sensitive to social and emotional stimuli and that is remodelled in early adolescence by the hormonal changes of puberty.185 The development of logical reasoning abilities and improvements in abstract and hypothetical thinking take place between the ages of 11 and 16.

The logical reasoning abilities of 16-year-olds are comparable to those of adults.186 The ability to consider the consequences of choices continues to improve in the following years.187 Unlike logical reasoning abilities, psychosocial capacities that improve decision making and moderate risk taking – such as impulse control, emotion regulation, the capacity to delay gratification, and resistance to peer influence – continue to develop well into young adulthood.188 These latter developments are not considered complete until approximately the age of 25.189 Psychosocial immaturity during adolescence may undermine what might otherwise be competent decision making.190

In other words, an adolescent’s brain matures first intellectually and then socially and emotionally. Such findings seem to be supported by statistical

185 See Laurence Steinberg, “Risk-Taking in Adolescence – New Perspectives from Brain and Behavioral Science,” (Current Directions in Psychological Science 2007, Vol.16: 55–9), 56 and Tomas Paus, “Mapping brain maturation and cognitive development during adolescence,” (Trends in cognitive sciences 2005, Vol.9, No.2: 60–8), 60. Both explain this as arising in part from an increase of white matter in the prefrontal cortex as a result of myelination, the process through which nerve fibres become sheathed in myelin, a white, fatty substance that improves the efficiency of brain circuits. More efficient neural connections within the prefrontal cortex are important for higher-order cognitive functions like planning ahead, weighing risks and rewards, and making complicated decisions.

186 See Raymond Corrado and Jeffrey Mathesius, “Developmental Psycho-Neurological Research Trends and Their Importance for Reassessing Key Decision-Making assumptions for Children, Adolescents, and Young Adults in Juvenile/Youth and Adult Criminal Justice Systems,” (Bergen Journal of Criminal Law and Criminal Justice 2014, Vol.2, No.2: 141–63), 144ff.

187 See Scott and Steinberg (2010), 34.

188 See Armin Raznahan et al., “Patterns of coordinated anatomical change in human cortical development: a longitudinal neuroimaging study of maturational coupling,” (Neuron 72, 2011, No.5: 873–84), who have conducted a longitudinal neuroimaging study of brain maturation looking into late childhood, adolescence, and early adulthood.

189 See Corrado and Mathesius (2014), 154. They even draw the conclusion that one might consider raising the maximum age for juvenile justice systems to 24 years (159).

190 Steinberg (2007), 56.

evidence showing that adolescents are overrepresented in incidents of every category of reckless behaviour.191

2.1.2. Hormonal changes

Another important biological aspect of the time between childhood and adulthood is puberty. Puberty involves elevated levels of gonadal steroid hormones which sculpt neural circuits; this leads to significant neuronal rewiring.192 Important changes in activity involving the neurotransmitter dopamine occur during early adolescence, especially around puberty.193 It has been claimed that there are substantial changes in the density and distribution of dopamine receptors in pathways that connect the limbic system, which is where emotions are processed and rewards and punishments experienced, and the prefrontal cortex, which is the “brain’s chief executive officer”.194 Dopamine plays a decisive role in how humans experience pleasure. Consequently, a change in the dopamine level leads to an elevated level of sensation seeking. Sisk and Zehr point out:

The recognition that the actions of pubertal hormones during adolescence have long-lasting consequences on brain structure and function raises fundamental questions that demand experimental study for a better understanding of the variables and interactions that influence behavioral maturation. […] Adolescence is clearly pivotal for behavioral development.195

Furthermore, increased levels of testosterone are associated with impatience, irritation and, consequently, aggressive and destructive behaviour.196 Steinberg

191 See Jeffrey Arnett, “Reckless behavior in adolescence: A developmental perspective,”

(Developmental review 12.4, 1992: 339–73), 339.

192 See Cheryl L. Sisk and Julia L. Zehr, “Pubertal hormones organize the adolescent brain and behavior,” (Frontiers in Neuroendocrinology 26, 2005: 163–74), 163, 170–1.

193 See Corrado and Mathesius (2014), 151.

194 Laurence Steinberg, “Should the Science of Adolescent Brain Development Inform Public Policy?,” (Issues in Science and Technology 2012: 67–78), 68.

195 Sisk and Zehr (2005), 171.

196 See Dank Olweus, Ake Mattsson, Daisy Schalling, and Hans Loew, “Circulating testosterone levels and aggression in adolescent males: a causal analysis,” (Psychosomatic medicine 1988, Vol.50, No.3: 261–72), 270.

suggests that it makes evolutionary sense that adolescents are more motivated by appetitive inclinations, more oriented towards sensation seeking, and more willing to take risks, for adolescence is the period during which individuals must leave the natal environment and seek out mates.197