'THRILL-SEEKING' GENE IDENTIFIED

Thrill-seekers as a group are more crime-prone than their risk-avoiding peers (See related article). Two new research studies indicate that people who seek out excitement -- whether legal or illegal -- are influenced, at least in part, by their genetic makeup.

Richard Ebstein and colleagues, at Herzog Memorial Hospital in Jerusalem, studied 124 unrelated Israelis. The researchers administered a test, devised by C. Robert Cloninger, which evaluated four personality traits: novelty seeking, harm avoidance, reward dependence, and persistence. They found that many subjects with high novelty-seeking scores had a slightly longer form of the D4 dopamine receptor (D4DR) gene than deliberate, reflective subjects. According to Ebstein, "this work provides the first replicated association between a specific genetic locus involved in neurotransmission and a normal personality trait."

Jonathan Benjamin and colleagues, at the National Institutes of Mental Health, conducted a similar study involving 315 subjects who were evaluated on five personality measures: extroversion, openness to experience, neuroticism, agreeableness, and conscientiousness. None of these traits showed any association with the D4DR gene. Novelty-seeking, however, was again associated with the long version of the gene.

Behavior researchers note, however, that the D4DR gene variant accounts for only about 10 percent of the variation in the trait of novelty-seeking. Cloninger suggests, also, that each personality trait is modified by other traits; thus, a thrill-seeker who is also biologically inclined to be reward dependent, persistent, and optimistic may be a successful business executive, while a thrill-seeker who is low in both reward dependence and anxiety may turn to criminal pursuits.

Researchers interested in the roots of thrill-seeking behavior have long been interested in dopamine, a neurotransmitter strongly linked to pleasure- and sensation-seeking behavior. Abnormal dopamine regulation has been linked to drug abuse, alcoholism, schizophrenia, and other mental and behavioral disorders, although some of the research is controversial.

Given that thrill-seeking is associated with criminality and an increased risk of death, why would genes for such a behavior survive? It's possible, a Psychology Today article pointed out recently, that thrill-seeking at one time was genetically advantageous. Psychologist Michael Aptor noted in the article that individuals willing to take risks would benefit an entire group (if not always themselves), by exploring new territory and making new discoveries -- for instance, about which foods were safe and which were poisonous. In a safer modern society, however, thrill-seeking -- particularly in combination with other risk factors such as low IQ -- may more often lead to dangerous and destructive behavior.

"Mapping genes for human personality," C. Robert Cloninger, Rolf Adolfsson, and Nenad M. Svrakic, Nature Genetics, Vol. 12, January 1996.

"Genes tied to excitable personality," Science News, Vol. 149, January 6, 1996.

"Risk," Paul Roberts, Psychology Today, Vol. 27, Nov.-Dec. 1994.

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