Adolescents’ risk-taking behavior is driven by tolerance to ambiguity

108

Previous work shows that the adolescent reward system is hyperactive, but this finding may be confounded by differences in how teens value money. To address this, we examined the neural ontogeny of objective value representation. Adolescent and adult participants performed a monetary gambling task in which they chose to accept or reject gambles of varying expected value. Increasing expected value had a stronger influence over gambling choices in adolescents relative to adults, an effect that was paralleled by greater activation in the ventral striatum in adolescents. This unique adolescent ventral striatum response remained even after matching groups on acceptance behavior. These behavioral and neural data suggest that the value of available options has a greater influence in adolescent versus adult choices, even when objective value and subjective choice are held constant. This research provides further evidence that hyperactivation of reward circuitry in adolescence may be a normative ontogenetic shift that is due to greater valuation in the adolescent brain.A dolescence is characterized by heightened sensitivity to rewards (1). This phenotype is subserved by exaggerated neural response in ventral striatum (VS) to the anticipation (2) and receipt of expected (3-5) and unexpected reward (6) in adolescents versus other age groups. The question remains, however, whether this effect is mediated by ontogenetic differences or simply a methodological consequence of using money as the rewarding stimulus. In other words, does the adolescent brain attribute greater value to available rewards, or is the effect driven by adolescents valuing money to a greater extent than adults because they typically have less access to and experience with it? The goal of this study was to disentangle these possibilities by examining subjective valuation (indexed by behavior) of objectively valued choices.Subjective value (SV) is defined as the value that an individual places on a stimulus (7). To make a choice, an organism determines the SV of each alternative and then selects the one with the greatest SV (8, 9). A recent metaanalysis of 206 studies of SV in adults identified the ventromedial prefrontal cortex (VMPFC) and VS as a "valuation system" (8). These regions represent SV during choice for monetary stimuli (10-14), charitable donations (15), consumer goods (16), and food (17)(18)(19). Despite the wealth of knowledge on the neural correlates of SV in adults, no previous studies have examined the neurobiological development of SV, which precludes ruling out the possibility that previous findings in support of a hyperactive adolescent reward system were confounded by differences in participant valuation.One approach to understanding the neural computation of SV is through measurement of expected value (EV), the sum of all of the possible outcomes of a particular choice multiplied by their probabilities (20). In adults, increasing EV yields parametric activation increases in bilateral VS, midbrain, medial prefrontal cortex (MPFC), an...

Section: Discussionsupporting

confidence: 90%

Neural representation of expected value in the adolescent brain

Barkley-Levenson

Galván

2014

108

“…There has been, however, disagreement about how and why attitudes toward uncertainty change with age (e.g., [1][2][3]. There has even been controversy about the basic decision-making preference structures of midlife adults.…”

mentioning

confidence: 99%

Like cognitive function, decision making across the life span shows profound age-related changes

Tymula

Belmaker²,

Ruderman³

et al. 2013

Self Cite

263

278

Significance Although largely unstudied, behavioral changes in decision making across the life span have implications for problems associated with poor decision making at different life stages, such as careless driving in adolescents and disadvantageous medical or financial decision making in older adults. We examine age-based differences in individual decision-making characteristics—choice consistency, rationality, and preferences for known and unknown risks—in 12- to 90-y-olds. We found that even the healthiest of elders show profoundly compromised decision making, and that risk attitudes show systematic changes across the life span that have important policy implications.

“…These mistakes were highly prevalent for up to 20 d of training. Monkeys did, however, gradually shift to an efficient maximization behavior like that shown by humans under these conditions (20,21), choosing the nondominated option only 2.91% ± 0.85% (monkey HU) and 4.53% ± 1.37% (monkey DE) of the time after training was complete (combining data from the first and second epochs) (SI Methods and Table S1). …”

Section: Resultsmentioning

confidence: 99%

Thirst-dependent risk preferences in monkeys identify a primitive form of wealth

Yamada

Tymula

Louie

et al. 2013

Self Cite

Experimental economic techniques have been widely used to evaluate human risk attitudes, but how these measured attitudes relate to overall individual wealth levels is unclear. Previous noneconomic work has addressed this uncertainty in animals by asking the following: (i) Do our close evolutionary relatives share both our risk attitudes and our degree of economic rationality? And (ii) how does the amount of food or water one holds (a nonpecuniary form of "wealth") alter risk attitudes in these choosers? Unfortunately, existing noneconomic studies have provided conflicting insights from an economic point of view. We therefore used standard techniques from human experimental economics to measure monkey risk attitudes for water rewards as a function of blood osmolality (an objective measure of how much water the subjects possess). Early in training, monkeys behaved randomly, consistently violating first-order stochastic dominance and monotonicity. After training, they behaved like human choosers-technically consistent in their choices and weakly risk averse (i.e., risk averse or risk neutral on average)-suggesting that well-trained monkeys can serve as a model for human choice behavior. As with attitudes about money in humans, these risk attitudes were strongly wealth dependent; as the animals became "poorer," risk aversion increased, a finding incompatible with some models of wealth and risk in human decision making. utility | satietyWhat We Know About Humans. Significant headway has been made toward understanding human choice behavior under risk. At a theoretical level, any logically consistent chooser behaves as if he consults a continuous monotonic internal representation of utility. Choice is then the process of maximizing utility (see ref.1 for a review). At an empirical level, consistent human choosers are typically somewhat risk averse, maximizing a weakly compressive utility function. Logically inconsistent choosers do not reflect such a maximization process (2-5), in principle.Less headway has been made in understanding how wealth level affects risk attitudes. Although a consensus view is that choosers should become less risk averse as wealth levels increase (6-8), solid empirical data have been difficult to obtain because wealth levels are hard to systematically manipulate in humans.What We Know About Animals. The risk attitudes of many species have been assessed, both with and without confirmation that choosers are logically consistent (9-11), with variable and sometimes controversial results (12). Caraco and colleagues (13), for example, found that sparrows were risk averse over food choices in a manner similar to that of humans, but that this depended on how many calories the subjects had already stored internally-a form of primitive consumption-related "wealth" shared by all animals and premonetary humans. When the birds were heavily food deprived (low caloric stores for future consumption or wealth), they became risk seeking. However, later studies in starlings challenged this conclusion, suggestin...