that evidence points to greater differences between early adolescents and mid- and later adolescents than between the two older groups. The authors suggested that more research is needed on the cognitive and noncognitive factors associated with mature decision making as needed.

In presenting initial results from an Australian study of 234 participants ages 12, 15, 18, and 21 years who were asked about several medical treatment vignettes, Bartholomew (1996) reported that 12-year-olds showed less evidence of decisional capacity than older participants. In contrast, 15-year-olds did not show significant differences from 18-year olds on measures related to comprehension and the amount of information sought. On other measures that related to reasoning capacities, however, 15-year-olds were more like 12-year-olds than they were like older participants.

A study by Bernhardt and colleagues (2003) of children’s views of participation in a genetic susceptibility study suggested that the children (ages 10 to 17 years) did not initially appreciate the study’s risks and potential benefits. When conversation encouraged them to “personalize” the possible consequences of genetic testing, they developed a fuller appreciation of the possible risks. This supports the emphasis on discussion in the design of the assent process.

Other research suggests that the development of decision-making capacities continues into adulthood, although “not all of these developmental changes point to increased rationality” (Millstein and Halpern-Felsher, 2001, p. 37). For example, certain biases in decision making may increase with age, including the tendency to reject evidence inconsistent with one’s views and accept evidence that supports them (Stanovich and West, 2000; Millstein and Halpern-Felsher, 2001; but see also, Klaczynski and Gordon, 1996 and Klaczynski and Narasimham, 1998).

Although a number of studies indicate that adolescents differ little from adults in certain elements of competent decision making, research overall suggests that abilities to comprehend important dimensions of research participation continue to evolve during adolescence. As the research reviewed earlier in this chapter made clear, adults are not always well informed and often show deficits in understanding related to research participation, especially when they are under stress. Overall, the committee concludes that it is usually advisable for parents to be involved in decision making about research participation for adolescents. Adolescents’ capacity to make informed decisions should not, however, be dismissed out of hand, especially when requiring parental permission would endanger adolescents or preclude their participation in research with important potential to benefit them or other adolescents in the future.

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