volitional       
adjective  formal uk/vəˈlɪʃ.ən.əl/ us/vəˈlɪʃ.ən.əl/
 行使意志的,选择的,决定的
acting as a result of a decision or choice; done because someone has decided or chosen to do it
  mental processes over which we have volitional control 我们能够通过意志控制的心理过程  
The action is not mechanical; it is volitional. 这个动作不是机械的,而是有意为之的。 
 - More examples
 - The complaints alleged volitional acts rather than accidental occurrences.
 - The purpose of the insanity defense is to ensure that a criminal sanction is imposed only on those who had the cognitive and volitional capacity to comply with the law.
 - This is a time of life in which you become a volitional consumer as opposed to being dressed by your parents.
 - The first drink may be volitional, but after one becomes addicted, it becomes a compulsion.