Since violence is a matter of perception as well as a measurable phenomenon, psychologists have found variability in whether people perceive certain physical acts as "violent". For example, in a state where execution is a legalized punishment we do not typically perceive the executioner as "violent", though we may talk, in a more metaphorical way, of the state acting violently. Likewise, understandings of violence are linked to a perceived aggressor-victim relationship: hence psychologists have shown that people may not recognise defensive use of force as violent, even in cases where the amount of force used is significantly greater than in the original aggression.