of a specific trait might be due to genes versus the environment.
Heritability estimates range from 0 (meaning that genes have no
influence) to 1.0 (meaning that genes determine everything).
The Minnesota Study of Twins Raised Apart or MISTRA is
a longitudinal study of twin pairs who were separated in infancy,
reared in different homes during their formative years, and united
as adults.^11 These twins went through some 50 hours of medical
and psychological assessments over a six-day time span at the
University of Minnesota Psychology Department and medical
school. As part of this extensive battery they were asked to take
Zuckerman’s Sensation-seeking Scale and the resulting heritability
estimates were around .55.^12 Others have had similar numbers up
to .58.^13 This means that genetics have a strong influence on sensa-
tion-seeking.
Back to Nick; when Nick jumped off the bridge, he was
flowing instead of freaking. He felt calm and hyperaware. Let’s
think about why. His brain was bustling from all of the dopamine
being released – making it a very pleasurable experience. In the
meantime, he might have less norepinephrine flowing through his
body, which means he felt energized but not out of control. Cortisol
was doing its work to keep his muscles taut and ready for anything
and his attention sharp, but he didn’t experience this as anxiety
because he was responding less than the rest of us would to the
serotonin. Put simply, for high sensation-seekers like Nick, this
extra arousal did not overwhelm him. It enhanced the experience.
Which leaves us with a very important question. If the
fight or flight response is designed to help us survive, why did
some of us evolve to respond to it differently? Jumping off
a bridge is potentially life threatening – so are many things that
high sensation-seekers do. It seems like high sensation-seeking
would have self-selected out of the gene pool a long time ago with
too many people falling to their doom jumping off cliffs. Here is the
paradox: There may be an evolutionary benefit to it.The Evolutionary Benefits of Sensation-Seeking
The central idea of Darwin’s theory of evolution is pretty straight-
forward and also sometimes misunderstood. When you mention
Darwin, people often blurt out “survival of the fittest,” which
makes it seem that evolution is some sort of biological cage
match pitting specific biological features against each other35 / Born to Be WildDownloaded from https://www.cambridge.org/core. Access paid by the UCSF Library, on 11 Nov 2019 at 14:20:40, subject to the Cambridge