Overall, when compared to age-matched control populations, mountaineers and BASE jumpers scored higher on the temperament measure of NS and the character measure of SD and lower on the temperament measure of HA and the character measure of ST, with only BASE jumpers scoring lower on the temperamental measure of RD. However, the relatively large variation evident in the standard deviations across the measures of temperament and character suggests that there is not a tightly defined personality profile among mountaineers and BASE jumpers, and that factors other than personality are also likely to contribute to engagement in these sports. Such factors may include opportunity and access to the natural climbing environment, peer influence, increased popularity, media attention, and commercialization of these activities.

There is a high correlation between Zuckerman’s SS and Cloninger’s NS scales [25], and, therefore, the finding of high NS in the research population is consistent with the previously demonstrated relationship between SS and participation in risk-taking sports [12–18]. According to Cloninger’s model of personality, high novelty seekers enjoy exploring unfamiliar places and situations. They are easily bored; try to avoid monotony and so tend to be quick-tempered, excitable, and impulsive; and enjoy new experiences and seek out thrills and adventures, even if other people think that they are a waste of time. NS is reinforced by a constellation of genetically determined neurotransmitters, particularly those in the dopamine/pleasure system [26, 27]. High NS and SS suggests that mountaineers and BASE jumpers have lower levels of circulating dopamine and therefore may be in a state of under arousal, which may in turn contribute to engagement in risk-taking sports.

There is also a correlation between Eysenck’s neuroticism (N) and Cloninger’s HA scales [25], and so the findings of low HA in our population are consistent with the finding of Freixanet’s study, which found that elite alpinists scored lower on N compared to controls and other mountaineers [14]. Forty percent of BASE jumpers and 17 % of mountaineers had extremely low HA scores. In a normal population, around 5 % have HA scores of 4 or less. The eight- and threefold increase in BASE jumpers and mountaineers, respectively, suggests that a large proportion have a temperament profile characterized by low HA. HA consists of a heritable bias in the inhibition or cessation of behaviors, while high scores are positively correlated with pessimistic worry in anticipation of future problems, passive avoidant behaviors such as fear of uncertainty and shyness of strangers, and rapid fatigability. The findings of low HA are therefore not surprising or counterintuitive, as individuals with low scores on this dimension are described as carefree, relaxed, daring, courageous, composed, and optimistic even in situations which worry most people. These individuals are described as outgoing, bold, and confident. Their energy levels tend to be high, and they impress others as dynamic, lively, and vigorous. The advantages of HA are confidence in the face of danger and uncertainty, leading to optimistic and energetic efforts with little or no distress. The disadvantages are related to unresponsiveness to danger, which can lead to foolhardy optimism [21].