Methods
(#) subjects participated in this study with ages ranging from # to # ,(# females and # males) all with normal or corrected-to-normal vision. All subjects received either course credit or payment for their participation.
The visual environment was developed using Open Inventor in an SGI Onyx2 computer and were presented to the subject via a head mounted display (V8, Virtual Research, liquid crystal display with a resolution of 640x3x480 per eye and a field of view of 60° diagonal). An immersive display has a great advantage over traditionally used desktop displays when studying human self-motion, in that it is much more natural and the experience of vection is much more salient and convincing.
The environment consisted of a straight, empty, seemingly infinite hallway with walls approximately 10 meters apart, a floor and no ceiling. Both the floor and the two walls were covered with a completely random dot texture. No repetitive patterns in the texture exist to serve as a tool for distance counting strategies. Additionally, there were no objects or landmarks at any point in the hallway.
The VR interface consisted of a stationary mountain bicycle. The rear tire of the bike was equipped with an infrared sensor that translated speed information to the above-mentioned SGI computer. A loud clicking sound was generated to indicate to the subjects when they had rode to the end of the trial distance. At the end of each trial distance, subjects were required to press the brakes in order to begin at new trial, at which time they were “transported” back to the beginning of the hallway.
Prior to the experiment the task expectations were explained to each subject and each subject was also given a series of practice trials to get used to both the equipment and the task expectations. Due to the physical nature of this task, subjects were told that they would be able to take a break at any point during the experiment to minimize fatigue and discomfort.
Essentially subjects were required to travel a certain distance and subsequently provide an estimate of the exact distance they had traveled. Subjects were presented with a pair of trial distances consisting of an initial reference trial (RT) and immediately following, a judgement trial (JT). Subjects were told to take note of the RT and subsequently ride through the JT and give a percentage distance estimation of the first trial (RT). For example, if the subject felt the second hallway (JT) was the exact same length as the first (RT) they would report an estimate of 100%, if the second was thought to be half of the first, the subject would report 50% and so on for any increment ranging from 1% to 200% (twice as long). Subjects were also instructed to ride at a speed that was most comfortable for them while attempting to maintain that same speed throughout the experiment.
This experiment consisted of three conditions. ….