Perception of Parallelism

Collaborators: Dr. Eric Hiris, Henry Rickman, and Joshua Phillips

Several famous illusions, such as the leaning tower illusion and the turn-in-the-road illusion, suggest that perspective can affect the perception of three-dimensional objects when viewing multiple pictures. To understand this effect, we directly measured the accuracy of perception of the orientation of objects when viewing multiple pictures. 

Participants viewed two pictures side-by-side, where each picture was either a sidewalk receding to the left, right, or straight ahead, a nature scene, or blank. Once the pictures disappeared, participants  were asked to rotate a line to match their perceived orientation of one of the sidewalks. Afterwards, participants were asked to rate, on a scale from 1-5, how parallel each pair of sidewalks looked. We compared the perceptions of the orientations of the sidewalks when they were next to another sidewalk picture to the perceptions of the corresponding sidewalk next to a blank picture. This is how we measured the misperception of the orientation of the sidewalks.