Dr. Samuel Putnam , an assistant professor of psychology at Bowdoin College in Maine, says thrill seeking behavior is mostly genetic, and that signs of it--from climbing the highest tree to swinging as high as possible on a swing set--can be recognized from very early ages.

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The desire to fly an airplane has been shown to represent one aspect of a sensation-seeking personality, a genetic trait associated with risky behavior involving driving, sex, sports and vocation, according to psychology studies.

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