Text3 In the past several years,as the nascent medium of virtual reality has come into its own,scientists and creators have begun to explore its potential effects on the human mind.Some are undoubtedly positive-as,for instance,when the technology is used to help war veterans overcome posttraumatic stress disorder,or as a means to expand a person"s capacity for compassion.But the immediacy of virtual reality has a dark side,too.Several months ago,Michael Madary and Thomas K.Metzinger,researchers from the Johannes Gutenberg University of Mainz,in Germany,published a series of recommendations on the ethical design and implementation of virtual reality.Their appraisal of the medium"s psychological force is both studious and foreboding."The power of virtual reality to induce particular kinds of emotions could be used deliberately to cause suffering,"they write."Conceivably,the suffering could be so extreme as to be considered torture."In filmmaking,the director must perform a kind of seduction of dread,leading viewers through an escalating series of psychological states.In the immersive world of virtual reality,no such dance is required.Part of the power of virtual reality-based horror comes from the fact that the director knows exactly where the viewer is looking."With that knowledge,we can play mind tricks or trigger events based on the gaze,"Jon Hibbins,the director of Psytec Games,a London-based virtual reality studio,said.For instance,he said,in Psytec"s most recent fantasy-horror title,Crystal RiR,"a monster can appear in a vent only when the player looks at the vent."Hibbins claims that,as viewers"brains are tricked into believing that they are physically present in a reality,the memories they form are much stronger than those made when watching so-called flat-screen media.To soften these memories,Hibbins and his team have introduced a slider into their game that allows players to control the intensity of the horror.""Normal"will be an average scare experience,"he said."You"Il hear voices in the distance,ghosts in the corridors,sound from the voids,and snakes in the corridors."Extreme"introduces jump scares,such as ghost figures that run through your body.It really does offer everyone an option."Stephan said,"Long-term,perhaps it"s a case of building literacy in players and viewers so they understand when the scares are coming.For now,I think that means taking it slow."32.The word"immersive"（Para.2）is closest in meaning to