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Navigating through real or virtual worlds requires a workable knowledge of the spatial layout. According to the landmark-route-survey model, metric spatial knowledge (survey knowledge) is acquired only following the acquisition of landmark and route knowledge. A dual mode model was proposed that assumes that survey knowledge may be quickly acquired for local regions. Research was conducted to understand how people rapidly acquire survey knowledge. Participants in three experiments brie y navigated on one oor of a virtual building, moving down hallways and performing tasks by using objects in rooms. Participants were later asked to answer from memory about the direction of objects by using pointing and map-drawing measures. A room effect was found for both measures; the angular positions of two objects in the same room were more accurately reported than those in different rooms. Accurate metric spatial information was available for objects in the same room, supporting an early acquisition assumption.

W r i g h t -P a t t e r s o n A i r Force Base, Ohio ABSTRACT A i r Force Aerospace Medical Research L a b o r a t o r y P r a c t i c a l c o n s i d e r a t i o n s make s u b j e c t i v e o p i n i o n one o f t h e most w i d e l y used methods t o assess mental workload. However, t h e v a l u e o f t h e d a t a o b t a i n e d by s u b j e c t i v e methods i s o f t e n l i m i t e d because s c a l e s a r e n o t s t a n d a r d i z e d and a r e n o t based on modern psychometric p r i n c i p l e s . T h i s paper d e s c r i b e s t h e development and v a l i d a t i o n o f a S u b j e c t i v e Workload Assessment Technique (SWAT) w h i c h uses c o n j o i n t measurement t o c o n s t r u c t i n t e r v a l l e v e l workload s c a l e s f r o m o r d i n a l r a n k i n g s o f combinations o f l e v e l s on t h r e e c o n t r i b u t o r y dimensions. An exDeriment was conducted t o i n v e s t i a a t e t h e c o n s t r u c t v a l i d i t v and c o n c u r r e n t v a l i d i t y ' o f t h e e c t o r group o f s u b j e c t s completes a s c a l e development phase and an e v e n t s c o r i n g phase. D u r i n g t h e s c a l e development phase, d a t a necessary t o develop a workload s c a l e a r e o b t a i n e d f r o m a group o f s u b j e c t s . D u r i n g t h e e v e n t s c o r i n g phase, s u b j e c t s r a t e t h e workload a s s o c i a t e d w i t h a p a r t i c u l a r t a s k and/or m i s s i o n segment. These a r e two d i s t i n c t e v e n t s and o c c u r a t d i f f e r e n t t i m e s . The e n t i r e SWAT procedure i s base upon an a p p l i c a t i o n o f a psychometric t e c h n i q u e known as c o n j o i n t measurement (Coombs e t a l , 1970, K r a n t z and Tversky, 1971). In c o n j o i n t measurement t h e j o i n t e f f e c t s o f s e v e r a l f a c t o r s Recommendations f o r f u r t h e r developme& a r e a r e i n v e s t i g a t e d and t h e r u l e o r c o m p o s i t i o n p r i n c i p l e t h a t r e l a t e s t h e f a c t o r s t o one another i s e x t r a c t e d f r o m t h e d a t a . One major advantage o f c o n j o i n t measurement and r e l a t e d s c a l i n g procedures i s t h a t o n l y t h e o r d i n a l aspects o f t h e d a t a a r e r e q u i r e d f o r t h e p r o d u c t i o n o f an i n t e r v a l l e v e l s c a l e which r e p r e s e n t s t h e j o i n t e f f e c t o f t h e f a c t o r s . The c a p a b i l i t y t o d e r i v e i n t e r v a l l e v e l d a t a f r o m s u b j e c t i v e judgements r e p r e s e n t s obvious advantages o v e r o r d i n a l l e v e l d a t a which t y p i c a l l y r e s u l t f r o m s u b j e c t i v e r a t i n g s . Because o n l y o r d i n a l p r o p e r t i e s o f t h e d a t a a r e needed t o generate a scale, t h e f i r s t s t e p i n t h e procedure i s t o o r d e r t h e dependent v a r i a b l e as a f u n c t i o n o f t h e j o i n t e f f e c t o f t h e f a c t o r s b e i n g i n v e s t i g a t e d . For example, degree o f workloa...

The Subjective Workload Assessment Technique (SWAT) has been used to assess mental workload in a variety of situations. As with subjective techniques generally, use of SWAT has emphasized relative comparisons of task conditions. For example, it has been possible to determine if one task or display required a greater mental worklaod than another. For many applications, however, it would be useful to have identified a critical SWAT level that indicates likely performance degradation caused by operator overload. A review of previously completed studies suggests a range of SWAT scores that were predictive of operator overload.

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