Limitations of the Study
Several methodological limitations need to be considered in interpreting the results of this
study. The population was not a random sample. All participants who volunteered were included.
This may have led to selection bias and the sample may represent a population of
particularly high-risk-taking BASE jumpers as 42% had suffered serious injury and 72% had
witnessed fatality or serious accident, yet persisted in the sport. BASE jumpers who had experienced
prior accidents may have been more motivated to share their experience and therefore
more likely to participate in the study. As the study included only active jumpers, cautious
BASE jumpers, who had given up the sport following an injury or a near-miss experience,
may have been excluded. Alternatively, the sampling process may have excluded particularly
high-risk groups as less experienced, more impulsive and higher risk-taking jumpers may have
been involved in fatal accidents at earlier stages of their BASE jumping careers and therefore
were unavailable for inclusion in the study.
Although the sample size is relatively small, it is likely to represent between 5 and 10%
of the total world BASE-jumping population. An added limitation may be the forced-choice
nature of the TCI questionnaire inwhich participants score either true or false for each question,
whereas the answermay lie somewhere in the middle. However, this is not rare in psychometric
tests of personality and there is extensive data showing the reliability and validity of the TCI
(Cloninger, 1987; Cloninger et al., 1994d; Cloninger et al., 1993). In addition, the findings of
the study were to a significant extent consistent with the study hypothesis. Finally, the choice
to engage in BASE jumping may have been influenced by cultural, environmental and familiar
background, which was not taken into account in the present study.