New Paper from Cooper Lab

A new paper from the lab of Dr. Emily Cooper, "How small changes to one eye's retinal image can transform the perceived shape of a very familiar object" has been published in The Proceedings of the National Academy of Sciences (PNAS), a peer reviewed journal of the National Academy of Sciences (NAS). The paper's authors, Iona R. McLean, Ian M. Erkelens, and Emily Cooper describe how a common distortion in glasses can trick your visual system into misperceiving object shapes.


"We describe and investigate a surprising visual illusion in which humans can misperceive the shape of a highly familiar object: their own mobile phone while they hold it in their hands. Unlike many other illusions that rely on sparse visual information, this shape illusion is robust in a fully natural environment. Our results suggest that this illusion results from a failure of the visual system to discard a single distorted visual cue. This failure informs our current understanding of sensory cue combination in natural settings and highlights the many factors that govern how we integrate information from multiple, potentially conflicting, sensory cues."


Vision can provide useful cues about the geometric properties of an object, like its size, distance, pose, and shape. But how the brain merges these properties into a complete sensory representation of a three-dimensional object is poorly understood. To address this gap, we investigated a visual illusion in which humans misperceive the shape of an object due to a small change in one eye’s retinal image. We first show that this illusion affects percepts of a highly familiar object under completely natural viewing conditions. Specifically, people perceived their own rectangular mobile phone to have a trapezoidal shape. We then investigate the perceptual underpinnings of this illusion by asking people to report both the perceived shape and pose of controlled stimuli. Our results suggest that the shape illusion results from distorted cues to object pose. In addition to yielding new insights into object perception, this work informs our understanding of how the brain combines information from multiple visual cues in natural settings. The shape illusion can occur when people wear everyday prescription spectacles, thus these findings also provide insight into the cue combination challenges that some spectacle wearers experience on a regular basis.

About the Image

Screen shot of graph from paper.

Spectacles with a monocular horizontal magnifier cause real objects to appear distorted under natural viewing conditions. (A) An image of a mobile phone held frontoparallel to the camera was warped to match the average shape ratio that participants drew when wearing the control spectacles (plano lenses). (B) The same image was warped to match the average shape ratio that participants drew when wearing the experimental spectacles with a monocular horizontal magnifier. The increase in length on the right side is equally split between the bottom and top right corners; however, participants varied in whether they saw equal or unequal stretching of top right and bottom right corners of their phones. (C) Bar heights indicate the average shape ratio: the ratio of the length of the right side of participants’ drawings to the left side. This includes drawings of their own phone (Left) and an unfamiliar square object (Right). The black dots in the figure represent each participant’s shape ratio. Ratios greater than 1 indicate that the right side was drawn taller than the left side, and ratios less than 1 indicate that the left side was drawn taller than the right side. Error bars represent the 95% CI and horizontal lines represent significant differences. If we assume that perceived shape is determined based on the binocular disparities created by the spectacles, and assume a typical viewing distance of 35 cm, we expect participants to see a shape ratio of 1.05 with the experimental spectacles on.

Read the Paper

Read in PNAS

Related Information

Perceptual Reality Lab