virtual reality article

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PergamonS0005-7967(96)00085-X

Behav. Res . Ther. Vol. 35, No. 2, pp. 153-158, 1997Copyright 1997 Elsevier ScienceLtdPrinted in Great Britain. All rights reserved0005-7967/97 $17.00 + 0.00

S H O R T E R C O M M U N I C A T I O N SV i r t u a l r e a l i t y a n d t a c t i l e a u g m e n t a t i o n i n t h e t r e a t m e n t o f s p i d e r

phobia : a case repor tALBERT S. CA RLIN, ~ HUN TER G. HOF FMA N 2'~'* and SUZA NNE WEGH ORS T 3

1Psychiatry and Behavioral Sciences, University o f Washington, 2Department of Psychology, University ofWashington and 3Human Interface Technology Laboratory, University of Washington, P.O. Box 352142,Seattle, WA 98195-2142, U.S.A.(Received 26 August 1996)

Summar y--Th is is the first case report to demonstrate the efficacy of immersive computer-generated vir-tual reality (VR) and mixed reality (touching real ob jects which patients also saw in VR) for the treat-ment of spider phobia. The subject was a 37-yr-old female with severe and incapacitating fear ofspiders. Twelve weekly 1-hr sessions were conducted over a 3-month period. Outcome was assessed onmeasures of anxiety, avoidance, and changes in behavior toward real spiders. VR graded exposuretherapy was successful for reducing fear of spiders, providing converging evidence for a growingliterature showing the effectiveness of VR as a new medium for exposure therapy. Copyright 1997Elsevier Science Ltd

INTRODUCTIONSpider phobia is characterized by persistent fear of spiders, an immediate anxiety response upon exposure to spiders, andavoidance of spiders. Fear of phob ic propor tions can interfere with the patient' s normal social routines, activities andinterpersonal relationships, and can produce marked distress about having the fear. The person typically recognizes thathis or her fear is excessive or unreasonable (American Psychiatric Association, 1994). Desensitization, a treatment basedon gradually and systematically exposing the phobic person to the feared object or situation, and calming them, hasproved to be an effective treatment for a wide range of phobias, including fear of spiders (e.g. Marks & Gelder, 1965).

Recent researchers have found the application of virtual reality to be effective in the desensitization of fear of heights(Rothbaum, Hodges, Kooper, Opdyke, Williford & North, 1995), and fear of flyingt (Hodges, Rothbaum, Watson,Kessler& Opdyke, 1996; Rothbaum, Hodges, Watson, Kessler & Opdyke, 1996) suggesting tha t a VR-based desensitiza-tion program may also be effective for the treatment of other phobias such as spider phobia. One potential advantage ofVR over other techniques lies in the greater ability of the patient or therapist to control the feared stimulus. Unlike areal spider, virtual spiders obey commands, can be placed in various positions and orientations by patient or therapist,and can be touched without danger. VR allows the experimenter to cont rol how frightening the spiders appear.Immersive virtual reality (VR) is a phenomen on in which an illusory reality is created in the mind of the computeruser. VR of ten involves comp uter simulat ions of real objects in near-real time. Observers typically wear helmets conta in-ing two small video monitors (one for each eye) attached to a high-speed computer. The image presented to one eye isslightly offset from the image presented to the other eye. In the real world, this offset provides a depth cue known as par-allax. In the virtual world, artificial parallax helps give participan ts the illusion th at they are in a 3-D space interac tingwith 3-D objects. With the aid of position tracking devices, the computer can monitor a person's physical movementsand adjust the images (and sounds) presented accordingly. Due in pa rt to these life-like changes in visual imagery in re-sponse to their own actions, Ss often report a feeling that they are "in a different place" when navigating the computer-simulated world. This subjective experience of presence in the virtual environment (e.g. Barfield & Weghorst, 1993) isthough t to be the essence of virtual reality (Laurel, 1995). In the present study, the place the patient visits is "SpiderWorld", a virtual kitchen and house that is home to two virtual spiders, a large furry brown one, and a smaller blackwidow with a white 3-D spiderweb.In o rder for VR therapy to be successful, desens itization must generalize to real spiders. Generally, the more similar asimulated environment is to the real environment, the better the transfer of training to the real world (Thorndike, 1931).Like mos t virtual worlds from the mid-1990s, our virtual environments were somewhat cartoon-like and required somesuspension of disbelief on the part of the user. In the present study, tactile augmentation (Hoffman et al., 1996) wasintroduced in an attempt to maximize the level of presence achieved and to maximize the transfer of training from VRto the real world. Tactile augmentat ion is a form of mixed reality where Ss feel posit ion- tracked real objects (with their

hand) that correspond to virtual objects they see in the immersive virtual environment.

*Author for correspondence at Human Interface Technology Laboratory.?Their study effectively combined treatment of anxiety management techniques (AMT) and VR exposure so the con-tribution of VR to success is suggested not definitive.~Y 35-2-C 15 3


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Sub j e c t h i s to r yM a r y M u f f e t i s a 3 7 - y r- o l d s in g l e w o m a n w h o h a s b e e n p h o b i c o f s p i d e r s f o r t h e p a s t 2 0 y r . A s a t e e n , s he b r ie f ly k e p ta p e t t a r a n t u l a i n a t e r r a ri u m . O n e d a y , w h e n s h e o p e n e d t h e t e r r a r i u m l i d , th e t a r a n t u l a j u m p e d f o r t h e f i rs t t i m e , a n dj u m p e d s u r p r i s i n g l y h i g h . A s a r e s u l t o f t h i s f r i g h t e n i n g e x p e r i e n c e , s h e g a v e i t a w a y . B u t s h e d e n i e s a d i r e c t l i n k b e t w e e nt h a t e v e n t a n d t h e o n s e t o f h e r p h o b i a . W h e n s h e w a s 1 7 y r - o l d h e r p a r e n t s w e r e o u t o f t o w n a n d t w o f r i e n d s s l e pt o v e r.

T h e f r i e n d s g r ew p a n i c k y w h e n t h e y e n c o u n t e r e d s o m e s p i d e rs in M s M u f f e t ' s h o u s e . M s M u f f e t t h o u g h t h e r f r i e n d sw e r e o v e r - r e a c t in g , a n d s h e c a l m l y c a r r i e d t h e s p i d e r s o u t d o o r s . A f e w d a y s l a t e r a f te r h e r p a r e n t s r e t u r n e d , s h e e n c o u n -t e r e d a s p i d e r in t h e h o u s e a n d d i s p l a y e d t h e s a m e p a n i c k y b e h a v i o r h e r f r i e n d s m o d e l e d f o r h e r a f e w d a y s b e f o r e .W h e t h e r t h e s e e v e n t s i n fl u e n c e d t h e e v e n t u a l o n s e t o f h e r s e v e r e p h o b i a i s u n k n o w n . T h e e t i o lo g y o f s p i d e r p h o b i a i sn o t w e l l u n d e r s t o o d ( K i r k b y , M e n z i e s , D a n i e l s & S m i t h , 1 99 5) .A t t h e t i m e s h e e n t e r e d i n t o t r e a t m e n t , a n y e n c o u n t e r w i t h a s p i d e r o r a s p i d e r w e b r e s u l t e d in p a n i c , w a v e s o fa n x i e t y , w e e p i n g , s h a m e a b o u t h e r ' o u t o f c o n t r o l ' b e h a v i o r , a n d s a d n e s s a b o u t h o w l i m i t e d h e r l if e w a s . M s M u f f e t ' se f f o r ts t o l i m i t h e r c o n t a c t w i t h s p i d e r s h a d s e v e re l y c o n s t r a i n e d h e r l if e. S h e c h o s e t o w o r k a ' g r a v e y a r d ' s h i f t o f h e r j o bt o r e d u c e c o n t a c t w i t h s p id e r s . P r i o r t o g o i n g t o w o r k , s h e t h o r o u g h l y w a s h e d a n d v a c u u m e d h e r c a r e v e r y d a y , t o w a s ho f f a n y s p i d e r s . S h e f r e q u e n t l y f u m i g a t e d h e r v e h i c l e w i t h p e s t i c i d e s , a n d a l s o l e f t c i g a r e t t e s b u r n i n g i n t h e a s h t r a y w i t ht h e w i n d o w s c l o se d , a f te r h e a r i n g f r o m a f r i e n d t h a t s p i d e r s a v o i d s m o k e . M s M u f f e t w o r e s p e c i a l ' s p i d e r g l o v e s ' w h i l ed r i v i n g , i n c a s e it w a s n e c e s s a r y to s w e e p s p i d e r w e b s o u t o f t h e c a r w i n d o w o n t h e w a y t o w o r k .P r i o r t o g o i n g t o s l e ep s h e s c a n n e d h e r r o o m a n d p l a c e d f o l d e d t o w e l s i n t h e d o o r j a m o f h e r b e d r o o m d o o r t o k e e ps p i d e r s o u t . A l l b e d r o o m w i n d o w s w e r e s e a le d w i t h d u c t t a p e e a c h n i g h t . T h e p a t i e n t w a s h y p e r v i g i l a n t, s e a r c h i n g fo rs p i d e r s w h e r e v e r s h e w e n t , a n d a v o i d i n g w a l k w a y s w h e r e s h e m i g h t e n c o u n t e r a s p i d e r . A f t e r w a s h i n g h e r c l o t h e s , s h ei r o n e d e a c h p i e c e o f c l o t h i n g , a n d p l a c e d e a c h i n d i v i d u a l p i e c e o f c l o t h i n g i n s id e a s e a l e d p l a s t ic b a g , t o m a k e s u r e i tr e m a i n e d f r e e o f s p i d e rs . O n e d a y , d e s p i t e a l l h e r p r e c a u t io n s , s h e f o u n d a l a r g e s p i d e r o n h e r c o u c h , a n d h a d a v e r yi n t e n s e re a c t i o n t o i t. S h e w a s b e c o m i n g h e s i t a n t t o l e a v e h e r h o u s e a t a ll b e c a u s e o f t h e c h a n c e o f e n c o u n t e r i n g s p i d e r s.H e r s i s te r u r g e d h e r t o s e e k t r e a t m e n t f o r h e r p h o b i a .B e c a u s e o f t h e o b s e s s i v e - c o m p u l s i v e q u a l i t y t o h e r d i t fi c u lt i es , a p h a r m a c o l o g i c a l c o n s u l t a t i o n w a s r e q u e s t e d t h a tr e s u l te d in a r e c o m m e n d a t i o n t h a t s h e u n d e r g o a t r ia l o f L u v o x . * A l t h o u g h t h e p a t i e n t w a s a m e n a b l e t o a p h a r m a c o l o g i -c a l a p p r o a c h s h e v i e w e d i t a s a l a s t r e s o rt a n d s t a t e d a p r e f e r e n c e fo r a b e h a v i o r a l a p p r o a c h .I n i ti a l t r e a t m e n t i n v o l v e d d i s c u s s io n s a b o u t t h e n a t u r e o f t h e a n x i e t y r e s p o n s e . S h e j u d g e d h e r s e l f t o b e e n g a g i n g i n i r -r a t i o n a l " o u t - o f - c o n t r o l , c r a z y b e h a v i o r " w h e n s h e e n c o u n t e r e d s p i d e r s. T h e p a t i e n t w a s e n c o u r a g e d t o l e a r n t o t o l e r a tea n d a c c e p t h e r a n x i e t y a s a c o n d i t i o n e d r e s p o n s e t o s p i d e r s t i m u l i t h a t c o u l d b e e v e n t u a l l y e x t i n g u i s h e d . S h e a c c e p t e dt h i s r e c o n c e p t u a l i z a ti o n w h i c h h e l p e d r e d u c e h e r c a t a s t r o p h i c i n t e r p r e t a t i o n s o f t h e a n x i e t y s h e e x p e r i e n c e d u p o ne n c o u n t e r i n g a s p i d e r .E a r l y t r e a t m e n t b e g a n w i t h e x p o s u r e t o f i e l d g u i d e p h o t o g r a p h s o f s p i d e rs . T h i s c r e a te d s t r o n g a n x i e t y a n d w a s b a r e l yt o l e ra b l e . A f t e r s e v e r a l s e ss i o n s t h e p h o t o g r a p h s b e c a m e m o r e t o l e r a b le a n d e v e n t u a ll y c r e a t e d l i t tl e d i s c o m f o r t .T r e a t m e n t t h e n p r o c e e d e d t o m o d e l s o f s p i d e r s , i n it i al l y a f la t p l as t i c H a l l o w e e n d e c o r a t i o n w a s a n x i e t y p r o v o k i n g , b u tw i t h i n t h r e e s e s s io n s o f e x p o s u r e , M s M u f f e t h u n g t h e p l a s ti c s p i d e r o b j e c t f r o m h e r t r u c k ' s r e a r v i e w m i r r o r a s a n o r n a -m e n t . O n e o f h e r c o l l ea g u e s g a ve h e r a g i f t o f a p a i r o f s i lv e r sp i d e r e a rr i n g s , w h i c h s h e c o u l d w e a r b u t f o u n d a n x i e t yp r o v o k i n g t o c l o s e ly e x a m i n e . A t t h e s a m e t i m e s h e w a s s u c c es s f u ll y e n c o u r a g e d t o b r o a d e n t h e r a n g e o f r o o m s s h e w a sw i l li n g t o e n t e r a n d o c c u p y a t h o m e .W h i l e t h e s e p r e l i m i n a r y e x p o s u r e s m a y h a v e h e l p e d p r e p a r e t h e p a t i e n t f o r t h e V R e x p o s u r e t h e r a p y t h a t f o l l o w e d ,t h e p a t i e n t w a s s t i ll e x tr e m e l y p h o b i c . S h e s t il l h a d m o s t o f t h e s y m p t o m s s h e h a d d i s p l a y e d w h e n s h e i n i ti a t e d t h e r a p y .T h e p a t i e n t s u g g e s t e d t h a t V R t h e r a p y m i g h t b e m o r e e f f e ct iv e . A l l p r e l i m i n a r y t r e a t m e n t s w e r e d i s c o n t i n u e d b e f o r eb e g i n n i n g t h e V R e x p o s u r e s a n d a l l m e a s u r e s r e p o r t e d b e l o w a d d r e s s t h e e f fi c ac y o f V R e x p o s u r e t h e r a p y o n l y .M e a s u r e s

S i x fe a r o f s p i d e r q u e s ti o n s w e r e c h o s e n f r o m a s e t o f 1 8 q u e s t io n s ( S z y m a n s k i & O ' D o n o h u e , 1 99 5) t o h e l p a s s e s s t h ee f f i ca c y o f V R t r e a t m e n t . P r e v i o u s r e s e a r c h e r s h a v e f o u n d t h e f u l l q u e s t i o n n a i r e t o h a v e e x c e l l e n t s p l i t h a l f r e l i a b i li t ya n d i n t e r n a l c o n s i s t e n c y , g o o d t e s t - r e t e s t c o n s i s t e n c y , c o n v e r g e n t v a l id i t y d u e t o i ts h i g h l y s i g n i fi c a n t c o r r e l a t i o n s w i t h ab e h a v i o r a l a v o i d a n c e t e s t ( r = 0 . 6 5 , P < 0 . 0 0 1 ) , a n d c o n s t r u c t v a l i d i t y i n i t s a b i l i t y t o d i s c r i m i n a t e p h o b i c s f r o m n o n -p h o b i c s a s m e a s u r e d b y a b e h a v i o r a l a v o i d a n c e t e s t ( O ' D o n o h u e & S z y m a n s k i , 1 9 93 ; S z y m a n s k i & O ' D o n o h u e , 1 99 5) .T h e s e q u e s t i o n s a r e d e s i g n e d t o m e a s u r e t h e p a t i e n t ' s a n x i e t y a b o u t s p i d e r s . B o t h b e f o r e a n d a f t e r V R e x p o s u r e t r e a t -m e n t t h e p a t i e n t r e s p o n d e d t o t h e f o l l o w i n g it e m s .

( 1 ) I w o u l d d o a n y t h i n g t o a v o i d a s p i d e r .( 2) I f I c a m e a c r o s s a s p i d e r n o w , I w o u l d l e a v e th e r o o m .( 3 ) I f I s a w a s p i d e r n o w , I w o u l d a s k s o m e o n e t o k i ll it .( 4 ) I f I s a w a s p i d e r n o w , I w o u l d b e a f r a i d o f i t.( 5 ) I f I s a w a s p i d e r n o w , I w o u l d f e e l p a n i c k y .( 6 ) I w o u l d f e e l v e r y n e r v o u s i f I s a w a s p i d e r n o w .U n l i k e O ' D o n o h u e a n d S z y m a n s k i ( 1 99 3 ) w h o c o u n t e d p o s i t i v e re s p o n s e s , w e a s k e d t h e p a t i e n t t o r a te e a c h i t e m o n a 1t o 7 sc a le . ( 1 = d o e s n o t a p p l y t o m e , 7 = v e r y m u c h a p p l i e s t o m e ) . T h e p a t i e n t a l s o c o m p l e t e d a s h o r t a b s o r p t i o nq u e s t i o n n a i r e ( T e l l eg e n & A t k i n s o n , 1 97 4) . T h i s m e a s u r e i s c o m p r i s e d o f 3 4 t r u e - f a l s e q u e s t i o n s d e s i g n e d t o a s s e s s t h eS ' s t e n d e n c y t o b e c o m e l o s t i n a d a y d r e a m o r m o v i e , ( e .g . " W h e n I l i st e n t o m u s i c , I c a n g e t s o c a u g h t u p i n i t t h a t Id o n ' t n o t i c e a n y t h i n g e l s e ") . T o s e r v e a s a s t a n d a r d o f c o m p a r i s o n , t h e f e a r o f s p i d e r q u e s ti o n s a n d t h e a b s o r p t i o n s u r -v e y w e r e a l s o a d m i n i s t e r e d t o 2 8 0 u n d e r g r a d u a t e s i n a n i n t r o d u c t o r y p s y c h o l o g y c o u r s e a t t h e U n i v e r s i t y o fW a s h i n g t o n .

* H e r o b s e s s iv e t h o u g h t s a n d c o m p u l s i v e b e h a v i o r s a s s o c i a te d w i t h t h e o b j e c t o f h e r f e a r s u g g e s t t h a t M s M u f f e t w a r -r a n t e d t h e d i a g n o s i s o f o b s e s s i v e - c o m p u l s i v e d i s o r d e r i n s t e a d o f a ' s i m p l e ' p h o b i a .


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Four presence questions adapted from Slater, Usoh and Steed (1994), and from Hoffman, Hullfish and Houston(1995) were used to assess how ' pres ent' the S felt in the virtual world. Hendrix and Barfield (1995) describe several stu-dies showing the reliability o f a similar subjective measure of presence. In our study, Ss were asked to rate on a scaleranging from 1 through 7:(1) How real did the virtual world seem to you? (1 = abou t as real as an imagined world, 7 = indistinguishable fromthe real world).(2) To what extent were there times when you felt that the virtual world became 'reality' for you, and you almost for-got about the real world outside? (1 = at no time, 7 = almost all the time).(3) Did the virtual world seem more like something you saw, or some place you visited? (1 = something I saw,7 = some place I visited).(4) In the virtual world, I felt more like... (1 = I was standing in the laborato ry wearing a helmet, 7 = I was in thevirtual room).

A p p a r a t u sThe VR system consisted of a Division ProVision 100, coupled with a Division dVisor@ head mounted display withthe fol lowing field of view characteristics: 40 degrees vertical, 105 degrees horizontal combined across two eyes, and 40-degree horizontal overlap. A 3-D mouse allowed Ss to move forward in the virtual kitchen by pushing a button. APolhemus 6D sensor attached to a fingerless bicycle glove (right hand) was used to control the position of the cyber-hand,* and a second sensor control led the position of the virtual spider. During tactile augmentation sessions, the latterwas attached to a furry toy spider.

T r e a t m e n tOver a period of 3 months, two of the authors (ASC, HGH) conducted 12 weekly sessions approximately 50 min long.Each session consisted of five, 5-min trials with a 2 or 3-min break between trials. The breaks were incorporated toreduce fatigue and reduce the likelihood of 'simulator sickness', a form of motion sickness sometimes evoked by VR,which wasn't a problem for our patient. The S was encouraged to interact with the spider in each situation long enoughfor her anxiety to decrease to a level where she felt ready to progress to a more frightening situation. She progressed ather own pace. Her anxiety level was assessed once a minute during exposure on a scale of 1 (no anxiety) to 10 (panic-level anxiety). The researchers were able to view what the S was doing in VR by looking at a video monitor, and wereable to interact with the patient appropriately. The therapist's comments were roughly similar to what would be expectedfor conventional in vivo exposure. The patient was sometimes encouraged to pick up the spider and/or web with hercyberhand and place it in orientat ions that were most anxiety provoking. Other times, the experimenter contro lled thespider's movements by physically moving a posit ion sensor, by entering new position coordina tes into the keyboard, o rby using preprogra mmed spider behaviors (unexpected jumps, etc). A large brown virtual sp ider with photograph-quali ty'texture-mapped' fur was used. A smaller black spider and an associated 3-D web were also introduced.Spiders were placed in a cupboard with a web, made to jump unpredictably upon being touched, made to climb ordrop in incremental jumps between the ceiling and the virtual kitchen floor, and they were touched, held and manipu-

lated by the S. The real-world counterpart of the brown spider, used for tactile augmentation, consisted of a palm-sizedreplica of a Guyana bird-eating tarantula. Coincidentally, this reminded the patient of her jumping pet spider mentionedearlier. Fur from the tail of a stuffed toy do g was glued onto the bod y of the toy spider. After 1 mont h (four, 50-minVR therapy sessions), tactile cues were first introduced into the virtual world using the tactile augmentation technique(Hoffman et al . , 1996). As the patient reached out with her cyberhand to explore the virtual object, her real handexplored the toy spider attached to a polhemus position sensor. The virtual spider now felt furry, and had weight(~cyberheft') and any movement of the toy sp ider caused a similar movement of the virtual spider.

RESULTS AND DISCUSSIONActivities in Spider World kept the patient's anxiety level relatively high throughout therapy. The highest rating foreach 5-min session was averaged for each day of therapy. The mean of these 12 daily anxiety scores was 7.9 on a scalefrom 1 to 10 where 10 = panic-level anxiety. Especially during the first month, the S often experienced physical symp-

toms concom mitant with her high anxiety ratings: dryness of the mouth, uncontroll ed shaking of the hands and legs,and profuse sweating (often visible), and r eports o f being on the verge of tears.Our de pende nt measure indicates significant progress. Pre to post-treatment changes in ratings o f subjective anxiety inresponse to specific activities with VR spiders showed strong evidence of anxiety reduction after 3 months of VR therapy.For example, the level of anxiety provoked by the tactile augmentation spider initially elicited very high ratings (shetried to rate it as 15 on a scale from 1 to 10 where 10 = panic-level anxiety, even though aware that 10 was the highestpossible rating). Her anxiety remained high for the next session o f tactile augmentation therapy before finally beginningto decrease (i.e. before the pa tient began to evidence habituation to the mixed reality spider). The mixed reality spider in-itially evoked such a strong emotional reaction tha t as she held the spider by its artificial fur with trembling hand, thepatient unintentionally shut he r eyes to reduce the anxiety (she later realized), and still displayed all of the physical symp-toms described above. In addition, she reported that she felt shaky several hours after she left the laboratory the night ofher first mixed reality spider treatment . After approximate ly 2 more months o f therapy, the mixed reality sp ider was nolonger effective in evoking a st rong emotional reaction; the same mixed-reality stimulus evoked a rating o f only 3, andno physical symptoms. After each therapy session, the pat ient engaged in deep muscle relaxation prior to leaving the lab.(She used this during the sessions as well.)Fear-of- spider ratings provide converging evidence for the overall efficacy of the therapy. Figure 1 shows the pati ent'stotal fear of spider rating (the sum of 6 ratings on a 7-point scale) relative to the distribution of such ratings for theundergraduate comparison group. Prior to treatment, only 1 undergraduate out of 280 had an equal or higher fear-of-

*We refer to the virtual representation of the subject's hand as a 'cyberhand'.


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156 SHORTER COMMUNICATIONSs p i d e r s r a t i n g t h a n t h e p a t i e n t . A f t e r 1 2 s e s s io n s o f V R d e s e n s i t iz a t i o n t r e a t m e n t , t h e p a t i e n t ' s f e a r r a t i n g s d r o p p e d c o n -s i d e r ab l y . T w e n t y - n i n e p e r c e n t o f t h e 2 8 0 u n d e r g r a d u a t e s t e s t e d ( i. e. 8 0 s t u d e n t s ) n o w h a d e q u a l o r h i g h e r t o t a l f e a r - o f -s p i d e r s c o r es t h a n t h e p a t i e n t .A l t h o u g h m o r e d i f f ic u l t t o q u a n t i f y , p e r h a p s t h e c l e a r e s t i n d i c a t i o n o f t h e e f fi ca cy o f t h i s t r e a t m e n t i s t h e d r a m a t i c r e -d u c t i o n i n d y s f u n c t i o n a l b e h a v i o r a f t e r t h e r a p y . T h e p a t i e n t b e c a m e l es s v i g i la n t o f sp i d e r s, n o l o n g e r e n g a g e d i n a n y o ft h e o b s e s s i v e - c o m p u l s i v e r i tu a l s a s s o c i a te d w i t h a v o i d i n g s p i d e rs , a n d r e p o r t s h a v i n g m u c h m o r e f r e e t i m e a v a i l a b l e a s ar e s u lt . S h e n o w s p e n d s m o r e t i m e o u t d o o r s a n d h a s r e c e n t l y g o n e c a m p i n g , s o m e t h i n g s h e w a s u n a b l e t o d o f o r t h e p a s t1 6 y e a r s b e c a u s e o f h e r s p i d e r p h o b i a .T h e t o t a l o f t h e a b s o r p t i o n r a t i n g s w a s a l s o c a l c u l a t e d f o r e a c h u n d e r g r a d u a t e a n d t h e p a t i e n t . T h e p a t i e n t ' s a b s o r p -t i o n s c o r e w a s i n t h e u p p e r 6 % o f t h e u n d e r g r a d u a t e d i s t r i b u t i o n , s u g g e s t i n g t h a t o u r p a t i e n t h a d a n u n u s u a l d i s p o s i t i o nt o b e c a p t u r e d b y e n t r a n c i n g s t i m u l i . O t h e r f a c t o r s c o n t r i b u t i n g t o t h e s u c c e s s o f t h e t r e a t m e n t w e r e t h e p a t i e n t ' s v e rys t r o n g m o t i v a t i o n a n d h e r a s s o c i a t e d s e l f - in i t i at e d e x p o s u r e t o s p i d e r s i n v i v o . F o r e x a m p l e , s h e l o o k e d a t a r e a l s p i d e rs h e f o u n d i n h e r k i t c h e n a t h o m e f o r 2 0 m i n , a n d c r u s h e d a n o t h e r l a r g e, r e a l s p i d e r w i t h s i g ni f ic a n t , b u t m a n a g e a b l eanxie ty , a l though no t spec i f ica l ly ins t ruc ted to do so . These se l f - in i t i a ted i n v i v o e x p o s ur e s p r o b a b l y p l a y e d a n i m p o r t a n tr o l e i n t h e t r a n s f e r o f t r a i n i n g f r o m V R t o t h e r e a l w o r l d . R o t h b a u m e t a l . (1995) repor t a s imi la r t endency in the i r fea r -o f - h e i g h t s s t u d y . I n t e r e s t in g l y , e x p e ri e n c e in t h e r e a l w o r l d m a y a l s o t r a n s f e r b a c k i n t o t h e v i r t u a l w o r l d . T h e p a t i e n tw a s m o r e e a s i l y f ri g h t e n e d b y v i r t u a l s p i d e r s d u r i n g t h e t h i r d w e e k o f t h e r a p y , a f t e r h a v i n g a f r i g h t e n i n g e x p e r ie n c e w i t ha r e a l s p i d e r e a r l i e r t h a t w e e k . T h i s o p e n s t h e q u e s t i o n o f w h e t h e r s o m e h y b r i d o f r e a l , v i r t u a l a n d m i x e d r e a l i t y e x -p o s u r e t r e a t m e n t s m i g h t b e u n i q u e l y e f fe c ti ve .

GENERAL D ISCUSSIONT h e p r e s e n t s t u d y s h o w s t h a t t r e a t m e n t o f s p i d e r p h o b i a i n V R ( a f o r m o f t r a i n i n g ) s uc ce ss fu ll y t r a n s f e r r e d t o t h e r e a lw o r l d . O u r c l i n i c a l p a t i e n t ' s f e a r o f r e a l s p i d e r s w a s a b a t e d b y e x p o s u r e t o v i r t u a l s p i d e r s . S y s t e m a t i c d e s e n s i t i z a t i o nw i t h V R g r a d e d e x p o s u r e w a s e f f e c t i v e i n r e d u c i n g r e p o r t e d a n x i e t y , a n d a v o i d a n c e o f r e a l s p i d e r s . T h e s e r e s u l t s c o n -v e r g e w i t h t h o s e o f o t h e r r e s e a r c h e r s ( e .g . R o t h b a u m e t a l . , 1 9 9 5 , 1 9 9 6 ) i n s u p p o r t i n g t h e u s e o f V R f o r t r e a t m e n t o fc l i n i c a l p s y c h o l o g i c a l d i s o r d e r s . T h e p r e s e n t s t u d y i s t h e f i r s t u s e o f i m m e r s i v e V R t o t r e a t s p i d e r p h o b i a , a n d t h e m o s ts e r io u s c l in i c a l c a s e t r e a t e d w i t h i m m e r s i v e V R e x p o s u r e t h e r a p y ( a s f a r a s t h e a u t h o r s a r e a w a r e ) . O t h e r p u b l i s h e d s t u -d i e s ( e .g . R o t h b a u m e t a l . , 1 9 95 ) f o u n d V R g r a d e d e x p o s u r e t o b e e f fe c ti ve i n t h e t r e a t m e n t o f e x p e r i m e n t a l S s w h or a t e d t h e m s e l v e s a s f e a r fu l o f h e i g h ts , b u t w h o h a d n o t s o u g h t t r e a t m e n t p r i o r t o b e i n g r e c ru i t e d b y t h e e x p e r i m e n t e r .H o d g e s e t a l . ( 19 9 6) r e p o r t a c a s e s t u d y o f a p a t i e n t w h o s o u g h t t r e a t m e n t f o r f e a r o f a i r t r a v e l s o s h e c o u l d g o o n v a -c a t i o n s w i t h h e r f a m i l y, a n d c o u l d t a k e a n e w j o b r e q u i r i n g t r a v e l. T h e i r S w a s p r o b a b l y n o t a s i n c a p a c i t a t e d b y h e r d i s -o r d e r , a n d a c c o r d i n g t o t h e a u t h o r s , t h e c o n t r i b u t i o n o f V R t o h e r p r o g r e s s i s u n c l e a r s i n c e a n o t h e r t r e a t m e n t w a sa d m i n i s t e r e d s i m u l t a n e o u s l y . O u r f i n d i n g t h a t V R t r e a t m e n t c a n b e e f fe c t iv e f o r s u c h a s e r i o u s a n d p e r v a s i v e d i s o r d e r isi m p o r t a n t . W h i l e t h e r e is g o o d r e a s o n t o b e o p t i m i s t i c t h a t t r e a t m e n t s e ff ec ti ve o n n o n - c l i n i c a l p o p u l a t i o n s w i ll a l s o b eef fec t ive on c l in ica l popula t ions , i t i s reassur ing to demons t ra te tha t genera l iza t ion .We in t roduced the f i r s t use o f t ac t i l e cues in VR therapy . Be ing ab le to fee l the v i r tua l sp ider was very e f fec t ive a t e l i -c i t i n g a s t r o n g e m o t i o n a l r e s p o n s e . T a c ti l e a u g m e n t a t i o n l e a d s t o t h e f o r m a t i o n o f c h i m e r i c m e m o r i e s t h a t a r e p a r t r e a la n d p a r t v i r t u a l ( H o f f m a n , i n p r e p a r a t i o n ) . T h i s b l u r r i n g o f t h e b o u n d a r y b e t w e e n r e a l a n d u n r e a l m a d e p o s s i b l e w i t hv i r t u a l a n d m i x e d r e a l it y l i ke l y h e l p s t h e t r a n s f e r o f V R t r a i n i n g t o t h e r e a l w o r l d .A s s u g g e st e d b y R o t h b a u m e t a l . ( 19 9 5) , f u t u r e r e s e a r c h s h o u l d e x p l o r e t h e u s e o f V R f o r t r e a t m e n t o f o t h e r p s y c h o -l o g ic a l d i s o r d e r s ( e s p ec i a ll y t r e a t m e n t o f a n x i e t y - re l a t e d d i s o r d e rs ) . O n e l i m i t a t i o n i n c a s e s t u d i e s s u c h a s t h e p r e s e n t o n ei s t h a t t h e y m u s t b e f o l l o w e d u p w i t h l a r g e r s t u d i e s t o i n s u r e g e n e r a l i z a b i li t y o f t h e f i n d i n g s .M u l t i - p a r t i c i p a n t V R w i l l a l l o w t h e c l i n i c i a n t o t a k e t h e f o r m o f a n a v a t a r w h o c a n i n t e r a c t w i t h a n d s p e a k t o t h ep a t i e n t i n s i d e t h e v i r t u a l e n v i r o n m e n t v i a a m i c r o p h o n e t h a t f e ed s i n t o t h e p a t i e n t ' s h e l m e t m o u n t e d d i s p la y . T h i s w i ll

6 0 -

50

.~ 400

~ 3o

~ 2oz

10

I I l l p a t i e n tO S t t r a m e n t a t i e n t ss c o r e5 10 15 20 25 30 35 40

F e a r - o f - s p i d e r s s c o r e sF i g . 1 . P a t i e n t ' s f e a r - o f- s p i d e rs s c o r e s c o m p a r e d t o u n d e r g r a d u a t e s .


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SHORTERCOMMUNICATIONS 157like ly increase Ss ' sense of p resence , which is though t to decrease as a t ten t ion is d is t r ac ted away f rom th e v ir tua l en-v ironm ent by conversa t ions with people in the lab room (Winn, Hof fm an & Osberg , 1995) .Ou r s tudy a lso bear s on th e is sue of whe ther the leve l o f p resence exper ienced by a pa t ien t in VR is re la ted to thetherapeut ic success of VR therapy . O ur pa t ien t exper ienced a m odera te leve l o f p resence before the sp ider was in troducedin the f irs t session, and always gave the highest ratings possible on the presence questions thereafter ( i.e . when exposedto the v ir tua l sp ider ) . Hodges et al. (1995) a rgue th a t the exper ience of a h igh leve l o f p resence may be necessary fore ffect ive immers ive VR therapy . Altho ugh n ot conc lus ive , our da ta is cons is ten t with tha t c laim. How ever r ecen t r esearchis us ing non- immers ive 3-D shut te r g lasses to make computer an imated sp ider s appear to hover be tween the pa t ien t andthe 2-D co mp uter sc reen (Goetes tam, Hollu p & Graaw e, 1996; Hollup , 1996). This use of desk top non- im mers ive com-pute r -an imated s t imuli does no t make Ss fee l p resen t in a computer - s imula ted environment . Desp i te th is f ac t , Hol lupand co l leagues have found the technique to be very e f fec t ive for exposure t r ea tment o f sp ider phobia . The ir da ta sugges ttha t ' ego ' p resence is no t a defining factor necessary for successful treatm ent o f pho bia w ith vir tual spiders (at least usingnon- imm ers ive equipment) . R a ther , ob jec t p resence , o r S s ' impress ion tha t the compute r -an imation sp ider is ac tua l ly' the re ' be tween the S and the computer sc reen , may contr ibu te to success fu l t r ea tment us ing the ir approach . Fu ture co l-labora t ive research compar ing the two techniques ( immersive V R an d 3-D shut te r g lasses ) is p lanned . A nothe r in te res tingissue for future research is whether th e level of presence experienced c an be predicte d beforeh and b ased on re ported per-sona l i ty charac te r is t ics such as abso rp t ion . T e l legen and Atk inso n (1974) descr ibed absorp t ion as a r ecep t iv i ty to exper i-ences of deep involvement , a he igh tened sense of r ea l i ty of the ob jec t be ing a t tended , and a d is regard for normallyd is t r ac t ing events . W e specula te tha t people with h igh a bsorp t ion ra t ings will fee l more presen t in v ir tua l r ea l i ty and wil lr espond more favorab ly to VR trea tment than people with low absorp t ion ra t ings .Researchers and a r t ists a re beg inning to explore the use of emotion to evoke a s t rong sense of p resence in VR. A sente r ta iner s move in to the VR marke t , they wil l l ike ly br ing with them a l l the t r icks of the movie t r ade (e .g . suspense ,emo tion-evok ing music , e tc . ) to m ake th e V R exper ience mo re e ffect ive . Fu ture research should explore the use of thesetechniques in v ir tua l the rapy .A c k n o w le d g e m e n t s - -T h e authors would l ike to thank Scot t Rousseau for computer model l ing and tex ture -mapping thebrown sp ider , and to Ar i Hollander for generous save- the-day sof tware programming (e .g . wr i t ing cus tom code to ge tone of the two cyberhands to change in to a b ig brown sp ider , e tc ) and t roubleshoot ing . Thanks to Jason Doctor forv a lu a b le c o mme n ts , a n d to th e US W e s t VRRV p r o je c t , AF OS R Gr a n t No . F 4 9 6 2 0 - 9 3 - 1 - 0 3 3 9 , D iv i s io n ln c , a n d th eo th e r HI T L a b c o n s o r t iu m me m b e r s f o r d o n a t in g VR e q u ip me n t a n d f o r g e n e ro u s s u p p o rt .

REFERENCESAmer ican Psychia tr ic Assoc ia t ion (1994) . Diagnostic and statistical m anual o f mental disorders (4th ed.) . Washington,DC: Amer ican Psychia tr ic Assoc ia t ion .Bar fie ld , W . , & W eghors t , S . (1993) . The sense o f p resence with in v ir tua l environments : A conceptua l f r amework . In G .

Sa lvendy & M. Smith (Eds . ) , Human computer interaction: Hardware and software interfaces (pp. 699-704).Am ste rdam: Elsev ie r.Goe tes tam, K. G. , Hollup , S . , & Graawe, R. W. (1996) . Virtual Reality in the treatment of spider phobia: A n experimentalcontrolled study. Paper presen ted a t the Wor ld Psychia try Congress in Barce lona .Hendr ix , C. , & Bar fie ld , W . (M arch , 1995). Presence in v ir tua l environme nts as a func t ion o f v isua l and audi tory cues.Proceedings o f VRAIS "95 . Los Alamitos , CA: Research Tr iangle Park , NC. IEEE Computer Soc ie ty Press .Hodges , L . F . , Rothbaum, B. O. , Kooper , R. , Opdyke , D. , Meyer , T . , de Graf t , J . J . , Wil l i fo rd , J . S . , & Nor th , M.(1995). Presence as the def in ing fac tor in a V R appl ica t ion . G eorg ia Ins t i tu te o f Technolog y , Graphics , V isua lizat ion ,a n d Us a b i l i ty Ce n te r, T e c h n ic a l Re p o r t GI T - GV U- 9 4 - 5 .Hodges , L . F . , Rothbaum, B. O. , Watson , B. , Kess le r , G. D. , & Opdyke , D. (1996) . A vir tual airplane for fe ar of flyingtherapy. Paper presen ted a t the mee t ing of the Vir tua l Rea l i ty Assoc ia t ion In te rna t iona l Sympos ium (VRAIS) , SantaC la r a , CA.Hof fm an, H . G. ( in prepara t ion) . Vir tua l source monito r ing accuracy for iden t i fy ing the sources o f ch imer ic mem or ies .Hof tman, H. G. , Groen , J . , Rousseau , S . , Hol lander , A. , Winn , W. , Wells , M. , & Furness I I I , T . (1996) . Tactile augmen-tation: Enhancing presence in inclusive V R with tactile feedba ck fro m real objects. Paper presen ted a t the mee t ing ofthe A mer ica n Psychologica l Soc ie ty, S an Franc isco .Hof fman, H. G. , Hullf ish , K. C. , & Hous ton , S . (1995) . Virtual-reality monitoring. Paper presen ted a t the mee t ing of theVir tua l Rea l i ty Assoc ia t ion In te rna t iona l Sympos ium (VRAIS) , Research Tr iangle , NC.Hoilup , S . A. (1996) . Vir tua l- rea l i ty therapy in the t r ea tment o f sp ider phobia . M as te r thes is , De par tm ent o f Psychology ,No r we g ia n Un iv e r s i ty o f S c ie nc e a n d T e c h n o lo g y , T r o n d h e im, No r wa y .Kirk by, K . C., Men zies, R. G., D aniels , B. A., & Sm ith, K. L. (1995). Ae tiolo gy of spider phobia: Classificatory differ-ences between two origins instruments . Behavior Research and Therapy, 8, 955-958.Laurel, B. (1995). Vir tual Reality. Scientific American, September, 90 .Marks , I . M. , & Gelder , M. G. (1965) . A contro l led re trospec t ive s tudy of behaviour therapy in phobic pa t ien ts . BritishJournal of Psychiatry, 111, 571-573.O'D ono hue , W. T. , & Szymanski , J . (1993) . Mechanism s of change in cogni t ive therapy in a s imple phobia : Logica lanalysis and empir ical hypothesis testing. Journal of Rational-Emotive and Cognitive Behavior Therapy, 11,2 07-2 22.Roth baum , B. O. , Hodges , L . F . , K ooper , R. , Opdyk e , D. , W il l i fo rd , J . , & Nor th , M. M . (1995) . Effec t iveness of v ir tua lrea l i ty graded exposure in the t r ea tment o f ac rophobia . American Journal of Psychiatry, 152, 626-628.Roth baum , B. O. , Hodges , L . F . , Watson , B. A. , Kessle r, G. D. , & Opdyke , D . (1996) . Vir tua l r ea l i ty exposure therapyin the t r ea tmen t o f f ea r o f fly ing : A case repor t . Behavior Research and Therapy, 34, 477-481.Sla te r , M. , Usoh , M . , & Steed , A. (1994). Dep th o f presence in v ir tua l environments . Presence: Teleoperators and VirtualEnvironments, 3, 130-144.Szymanski, J . , & O'D ono hue , W. (1995). Fear o f Sp ider s Q ues t ionna ire . Journal of Behavioral Th erapy and ExperimentalPsychiatry, 26, 31-34 .Thorndik e , E . L . (1931) . Human learning. Ne w Yo r k a n d L o n d o n : T h e Ce n tu r y Co .


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158 SHORTERCOMMUNICATIONSTellegen, A., & Atkinson, G. (1974). Openness to absorbing and self-alter ing experiences ("absorption") , a trait relatedto hypnotic susceptibility. J o u r n a l o f A b n o r m a l P s y c h o l og y , 8 3 , 268-277.Winn , W. , Hof fman, H. G. , & Osberg , K. (1995) . Sem iotics an d the design o f objects , actions and interactions in virtual en-vironments. Paper presen ted a t Amer ican Educa t iona l Research Assoc ia t ion , San Franc isco , CA. Also to be publ ishedin In terna t ional Journal o f Educat ional Psychology .

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