Traditionally, the criminal law adopts the classical approach and assu
mes people have the ability to regulate their behaviour so as to compl
y with its rules, although there are recent signs that the courts are
looking more carefully at human capacity. Research in psychology and b
iology, albeit still in its early stages, suggests that individual tra
its which influence the capacity for self-control vary from one person
to another. This article considers the potential impact of this data
on the determination of responsibility under the criminal law.