FORUM ShortPapers TheRealityofExperience:Gibson©sWay Abstract about the appropriate ‘‘rulers’’ for describing that real- ity.This is true for behavioral sciences as well as for This paper considers some rst principles thatmight provide physical sciences. The question ofthe measure for ‘‘real- abasis for an objective science ofexperience (presence or ity’’ is also afundamental starting point for theories and immersion). Dimensions thatare considered include classical measures ofvirtual environments. What are the appro- Newtonian measures ofthe distal stimulus, changes in neural priate rulers for measuring the experiences in virtual en- mechanisms reecting theproximal stimulus, information vironments and for comparingthose experiences against theoretic measures ofthe statistical properties ofevents, and the experiences ofreality? As the title ofthis article indi- functional properties related tointentions and abilities. Gib- cates,I have abias. Ibelieve that the assumptions under- son’s ecological framework is suggested as apromising func- lying Gibson’s (1979) ecological approachprovide a tional approach for dening thereality ofexperience in rela- promising basis for framingquestions of‘ ‘presence’’ and tionto theproblem ofdesigning virtual environments. This ‘‘immersion’’ with regard to virtual environments. approach emphasizes thetight coordination between per- However, the goal ofthis article is not toconvince read- ception and action and xes themeasurement coordinate ers ofthis position, but simply to heighten awareness to system relative tothecapacity for action. the assumptions and existential commitmentsthat shape our theoretical and experimental perspectives on experi- ence. 1Introduction Inthe early stages ofthis [relativity] theory,its name 2Newton©sWay led to the erroneous impression that this approachin science is based on the philosophic view of‘relativ- Newton chose space and time as the absolutes for ism’— the idea that all knowledge is relative only to his program.Thus, space and time were considered as the ‘knower’— i.e.,that there is no objective knowl- dimensions ofacontainer whose existence was indepen- edge to talkabout. Of course, Einstein never had this dent ofthe objects contained within. This container view in mind—his approachwas just the opposite, then becamethe basis for an ‘‘objective’’ description of where one focuses onthe invariant (objective) law of an object or event. Itbecamethe measure ofreality . nature. To avoid confusion, Einstein tried to rename Fechner (1860/1966) extended Newton’s programinto his theory‘invariententheorie’(theor yofinvariants), the field ofpsychology ,arguing that ‘‘it is only the physi- implying afocus ofthis theoryon absoluteness rather cal that is immediately open to measurement,whereas than relativeness. However, he eventually rejected the the measurement ofthe physical canbe obtained only as namechange because offurther confusion hethought dependent on the psychical’’ (p.8). Thus, Fechner boot- it mightentail. (Sachs,1993, p. 4) strapped his programon the sameexistential commit- Any science begins with some assumptions about the fundamental nature of‘ ‘reality’’ —whether there is an absolute, objective, reality independent ofthe observer orwhether the factsof reality are only relative to an ob- John M.Flachand server. These assumptions guide our choices or guesses John G.Holden PsychologyDepartment WrightState University Presence, Vol. 7, No. 1, February 1998, 90–95 Dayton,OH 45435 r 1998by theMassachusetts Institute of Technology [email protected] 90 PRESENCE:VOLUME7,NUMBER1 Flachand Holden 91 mentas Newton. For the mostpart, experimental psy- insights are not pertinent atthe scale ofhumanbehavior; chology remains committedto Newton’s basis in which toargue that Einstein’s insights have implications for three-dimensional space and time (e.g.,chronometric atomic and cosmic scales ofreality ,but not for reality at analysis) are the absolutes against which to measure be- the ecological scale. For psychology this argumentleads havior and experience. naturally to aview ofthe environment as objects distrib- uted within acontainer with dimensions ofspace and time.The container and the objects within are consid- 3Einstein©sWay ered to have an absolute existence independent fromthe animal being studied. For those working in the Fechne- Einstein, along with manyothers (e.g.,Galileo, rian tradition, Newtonian measures becomethe touch- Huygens,Leibniz) questioned the decision to use space stone for reality.Classical measures ofspace and time and time as absolutes. Einstein argued that there was no becomethe defining properties ofastimulus. They de- ‘‘objective’’ test (i.e.,experiment) that could distinguish fine the ‘‘real’’ object. Humanexperience is measured the difference between uniform motion and absolute against this reality.The implication for virtual reality sys- rest. The implication was that space and time were rela- tems is that fidelity is defined in relation to the corre- tive to areference frameand thus could not be the basis spondence between the simulated world and the ‘‘real’’ for bootstrapping ascience committedto realism. Space world asmeasured using the ruler and clockof classical and time could not bethe measure ofreality .These mea- physics. Thus, we have constructs of‘‘real time’’ and sures were not observer independent. The relative na- ‘‘real distance’’ against which we can comparethe ‘‘vir- ture ofspace and time creates adilemma—either relin- tual times’’ and ‘‘virtual distances.’’ quish the commitmentto realism, to objectivity,and maintain space and time asthe basis for measurement, or,find anew basis. Einstein refused to give upthe com- 5Helmholtz©sWay mitmentto realism and chose instead to realign his basis for reality.This commitmentled tothe choice ofthe Helmholtz (e.g.,1962) chose tobootstrap the speed oflight as the absolute upon which to bootstrap psychological programon biology.Henoted the differ- measures ofreality . ence between the ‘‘distal’’ stimulus, that could bede- Einstein’s choice, obviously,has had revolutionary fined in classic Newtonian terms and the ‘‘proximal’’ implications for our view ofthe physical world. Because stimulus, which could bedefined in terms ofchanges in the speed oflight has dimensions ofspace and time, sensorymechanisms.With the emphasis on Mu¨ller’s these dimensions which in Newton’s programwere or- ‘‘law ofspecific nerve energies,’’ Helmholtz chose bio- thogonal are now viewed as dependent. The speed of logical mechanisms as the basis for objectively defining light provided amappingfrom space to time and vice the stimuli ofexperience. Thus, for those who follow the versa. Sucha mappingwas inconceivable within the Helmhotzian tradition, the structure ofnerves, eyes, Newtonian program.But what are the implications for a ears, muscles, brains, and soonbecomefundamental science ofcognition and behavior? What are the implica- touchstones for understanding the experience ofreality . tions for ascience ofexperience? What are the implica- With this approach,the ‘‘acid’’ test ofatheoryis the tions for technologies such as VRwhose objective is to ability tobe‘‘objectified’’ or instantiated by an underly- shape experiences? ing biological mechanism.This approachleads naturally toconstructs such as ‘‘visual space’’ or ‘‘auditoryspace’’ 4Fechner© sWay where the experience ofspace and time are specific to the biological mechanisms that mediate the experience. Oneresponse is to persevere with the commit- The implication ofthis approach for virtual reality is that ments ofNewton and Fechner—to argue that Einstein’s fidelity is defined relative to the ability tosimulate the 92 PRESENCE:VOLUME7,NUMBER1 biological mechanisms—the proximal stimulus. Thus, binocular and binaural inputs mightbe considered es- sential to ahigh-fidelity experience ofspace. 6Broadbent©sWay Broadbent (1971), Miller (1956), and others chose to emphasize principles ofcontrol and communi- cation as the grounds for bootstrapping studies ofexpe- rience. Inthis programthe properties ofcommunication channels and control systems provided the basis against which to measure reality.This foundation allowed the Figure 1. Alternative views of aclosed-loop information processing abstraction ofinvariant principles using information system.The traditional representation (A)treats stimulus and response theory,control theory, and signal detection theory.For as distinctand external tothe coordination. The alternative those who have followed Broadbent’s lead, stimuli are representation (B) illustrates Dewey’s intuition thatthe stimulus and defined in terms oftheir statistical properties (e.g.,bits response are coupled within the coordination. per second or probability density functions). With this approach,emphasis was shifted fromthe classical New- tonian dimensions ofspace and time and the biological ton/Fechner’s view ofthe information processing sys- dimensions ofneural activity to dimensions that re- temas contained within an environment. Stimuli and flected the observer’s expectations. The probability or responses are seen asdistinct and are represented asex- likelihood ofan event becamea defining feature against ternal tothe coordination. They are ofthe environment, which to measure the experience ofthat event. This ap- not intrinsic tothe coordination. The representation in proach suggests that information processing rate,sensi- Part Bis identical, in terms ofcontrol theory.However, tivity,bias, and stability mightprovide the best measures the impression