Body-scaled information for affordances in a virtual environment

Introduction: The affordances available to an individual are scaled to the individual’s body. This scaling factor is important because it links object or environment properties and individual’s dimensions through an invariant value. This means there is a lawful relation underpinning (at least some) affordances. For instance, participants deem a stair climbable without the aid of hands if the raiser is smaller than 0.88 their leg length (Warren, 1984), and participants walking through a door rotate their shoulders over their longitudinal axis if the aperture is smaller than 1.4 the width of their shoulders (Warren & Whang, 1987). In the present study we replicated Warren and Whang’s study in a virtual environment. Methods: Participants were 24 students who used a Kinect Natural User Interface to control an avatar passing through apertures. Participants performed 32 trials for each of 2 speed conditions and 4 practice sessions. There were two avatar conditions. The standard avatar condition displayed a standard avatar which responded only to shoulder rotation, while in the similar avatar condition it displayed similar kinematics and morphology to the participant. We identified the critical ratio after which participants rotated their (and the avatars’ shoulders) to pass through apertures. Results: After the first session, critical ratios decreased significantly and there were barely any collisions. Participants showed larger ratios with the faster speed and with the similar avatar. With the standard avatar the ratio was 1.40 while with the similar avatar the ratio was 1.57. Discussion: Participants learned to use the information available in this virtual environment to pass through apertures, and in doing so disclosed a critical ratio very similar to that found in a real environment. We will discuss implications for our view of affordances and applications to virtual environments.