Eyes can trick mind to create incorrect assumptions about objects: study

Washington: Scientists have found that the human visual system can trick the brain into generating incorrect assumptions about the size of objects.

Experts think the discovery changes how people perceive many aspects of everyday life including driving and eyewitness accounts in the criminal justice system. This is also likely to have implications for security issues like drone sightings and UFOs.

"In order for us to determine the real size of objects that we see around us, our visual system needs to estimate the distance to the object. We can be fooled in our estimates of object size. Photographers take advantage of this using a technique called ’tilt-shift miniaturisation’, that can make life-size objects appear to be scale models," said Daniel Baker from the University of York’s Department of Psychology.

For the study, participants were asked to compare photographs of railway scenes. There were two sets of images. In one set, images were of full-scale railway scenes and the upper and lower parts of the photographs were blurred. In the second set, images were small-scale models and their edges were not blurred. When people were asked to identify which images were real full-scale railway scenes, blurred ones were perceived to be smaller than the models.

"To arrive at an understanding of absolute size it can take into account the parts of the image that are blurred out – a bit like the out-of-focus areas that a camera produces – which involves a bit of complicated mathematics to give the brain the knowledge of spatial scale," explained Baker.

Experts now think that the human visual system is highly flexible and sometimes the eyes are capable of accurate perception of size by exploiting what is known as ‘defocus blur’. However, other times, eyes are subject to influences and fail to make sense of the real-world object size.