Evaluating the accuracy of size perception in real and virtual environments

Accurate perception of the size of 3D objects depicted on 2D desktop displays is important for many applications. Whether users perceive objects depicted on a display to be the same size as comparable real world objects is not well understood. We propose using affordances judgments as a way of measuring the perceived size of objects depicted in desktop virtual environments and the real world. The methodology involves indicating whether or not a particular action can be performed in a given environment, making it a flexible measure that can be used across different display technologies. In two studies, we test users' perceptions of size by asking them to make affordance judgments in both the real world and a geometrically matched desktop virtual environment. In the first study, users judge whether they can grasp an object and in the second study, they judge whether they can fit their hand through an opening. In both experiments we show that users perceive the size of objects in the desktop virtual environment to be smaller than in the real world.