propensity

Why do some people have a propensity for/toward violence? [=why are some people violent?; why do some people have a tendency to be violent?]为什么有些人有暴力倾向？

He had a propensity for crime.他曾有犯罪倾向。

She has a propensity to assume the worst. [=she tends to assume the worst]她倾向于做最坏的假设。