The study aimed to compare two competing theoretical explanations for young adult risk taking. A cognitive developmental theory was compared with a psychosocial developmental theory identifying a new life phase: emerging adulthood. The primary risky behaviour investigated was speeding down an open highway. Three hundred and eight participants aged 18 to 66 completed an internet questionnaire. The hypotheses that self-perceived likelihood of speeding would decrease with age and that males would report greater likelihood of speeding were supported, with no interaction between gender and age. Contrary to expectations, the number of consequences anticipated as a result of speeding did not increase with age; rather the number of positive consequences anticipated decreased with age and this mediated the relationship between age and anticipated likelihood of speeding. Younger participants were less future oriented, more present oriented and more sensation seeking than older participants. Sensation seeking mediated the relationship between age and self-reported likelihood of speeding. The impact of life experiences on anticipated risk taking was investigated using a mixed methods approach combining quantitative and qualitative data. The results suggested a number of life experiences which were perceived to affect risk taking and could be investigated in future research. The findings generally supported the psychosocial developmental explanation for risk taking in early adulthood and suggestions for further research are given.