One form of this involves failure to recall particular past events, possible in a particular period. In another form there is failure to register current events and subsequently to recollect them. In both cases the memories may influence behaviour although they resist efforts at recollection. Such memories are usually painful and are repressed as a psychological defence. (It is characteristic that they may be recovered under hypnosis). Analogous phenomena may occur in the case of collective memory. In bureaucratic environments they are associated with the process of burying some unpleasant file of information, if only by severely restricting its distribution. Or alternatively it will be carefully arranged that no lies is created in the first place. The media and politicians often act on the assumption that the public will forget some unpleasant item of information.