Abstract
The invariable relationship between the absolute distance of an object and its retinal size is widely known and people use this for their size and distance perception in the 3D world. Familiar objects of known size can help size/distance perception. But often we experience the 3D world through 2D images such as pictures or television. In this study, we tested whether images of familiar objects can improve people’s perception of an object’s size and distance in a 2D scene. In a series of online experiments run on Pavlovia, participants viewed a target black rectangle representing their smartphone rendered within a 2D scene. They either positioned it in the scene at the distance they thought was correct based on its size (P/S task), or made the target the correct size based on its position in the scene (S/P task). Some participants saw the scene with familiar objects (n= 84) and the others saw the scene without (n= 134). In the group that saw the scene with familiar objects, participants made the targets significantly smaller for the S/P task compared to the target size they had chosen at those same positions during the P/S task (p= .004). However, there was no difference between tasks for the group without familiar objects (p= 1.000). Further evaluation revealed that the targets were made significantly smaller for the P/S task in the presence of familiar objects compared to without familiar objects (p= .001), but not for the S/P task (p= .598). This result show that familiar objects may act as anchors for observers to use when determining an object’s size and distance in a 2D scene beyond the simple geometry provided by the horizon and ground plane, but they may affect the perception of size and distance differently in a 2D scene.