To the extent that common evolutionary pressures have led adolescents of a number of species to exhibit certain shared behavioral attributes, these behavioral commonalities may reflect similar underlying biological substrates, with brain regions undergoing particularly marked changes during adolescence highly conserved. Indeed, human adolescents and their counterparts in other species share numerous similarities in hormonal changes, behavioral characteristics and brain transformations ( Spear, 2000), including alterations in reward-related circuitry ( Ernst & Spear, 2008), suggesting that these adolescent-typical characteristics may reflect in part hard-wired, evolutionarily sculpted systems.Īdolescent-characteristic behavioral changes, including enhanced interactions with peers and increases in risk taking, sensation and/or novelty seeking are evident across a variety of species, and seemingly have evolved in part to facilitate emigration by providing the impetus to search for new territories, sexual partners, and new sources of food ( Spear, 2000, 2007a). Although adolescence is sometimes thought of as a unique phase of human development, developing organisms of all mammalian species go through a similar transition from dependence to independence. Implications of these findings for adolescent substance abuse will be discussed.Īdolescence is a time of rapid physical change, along with sometimes striking alterations in mood and behavior. Additional experiments designed to parse specific components of reward-related processing using natural rewards have yielded more mixed findings, with reports of accentuated positive hedonic sensitivity during adolescence contrasting with studies showing less positive hedonic affect and reduced incentive salience at this age. After reviewing these topics, the present paper discusses conditioned preference and aversion data showing adolescents to be more sensitive than adults to positive rewarding properties of various drugs and natural stimuli, while less sensitive to the aversive properties of these stimuli.
For instance, adolescent rats, like their human counterparts, exhibit elevations in peer-directed social interactions, risk-taking/novelty seeking and drug and alcohol use relative to adults, along with notable changes in motivational and reward-related brain regions.
Adolescence is an evolutionarily conserved developmental phase characterized by hormonal, physiological, neural and behavioral alterations evident widely across mammalian species.
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