There is a popular saying that we should not believe everything we hear, highlighting the importance of trusting only what we see with our eyes.

However, recent research has raised doubts about the reliability of our visual perception too. The study was carried out by a team hailing from the University of York and Aston University, both located in England.

The participants were shown photographs featuring life-sized railway scenes where intentional blurring affected the upper and lower sections. Additionally, they were presented with photographs of smaller-scale railway models that were not blurred.

The objective was to compare the images and determine which one represented the actual full-scale railway scene. Interestingly, people consistently perceived the blurred real trains as smaller in size compared to the models.

Dr. Daniel Baker from the University of York said that the visual system heavily relies on estimating distances to determine the true size of objects. 

This estimation process takes into account the blurred areas in an image, similar to the out-of-focus regions captured by a camera, but the study revealed that individuals can easily be deceived in their estimations of object size.

Photographers have long taken advantage of this phenomenon through a technique called “tilt-shift miniaturisation," creating the impression of life-sized objects appearing as scale models.

The findings of this particular study demonstrate the remarkable adaptability of the human visual system. While it can accurately perceive size through defocused blur in certain situations, it is also susceptible to other influences that can lead to errors in judging the actual size of objects.

Professor Tim Meese, from Aston University, said, “Our results indicate that human vision can exploit defocus blur to infer perceptual scale but that it does this crudely.”

According to him, the results offer a fresh understanding of the computational processes employed by the human brain when making perceptual judgments about our interaction with the surrounding environment.

However, don't feel bad if these photos have deceived you. Our perception of the world might not be the most accurate, but it has evolved in a way that benefits our survival the most.

By manipulating the context and rewards of visual tasks, another researcher team found that our visual perception, even at the retinal level, changes to maximize personal benefits.

This suggests that cognitive biases may not only affect our decision-making process but also alter our fundamental perception.

ETH Professor Rafael Polania and University of Zurich Professor Todd Hare led a study that shows we unconsciously see things distorted when it comes to our survival, well-​being, or other interests.

Polania and his coauthors were able to prove through a series of experiments that people perceive the same things differently when the decision context changes. The 86 participants were asked to repeatedly compare two black-​and-white striped patterns – known as Gabor patches – and say which pattern was closer to a 45-​degree angle. The aim was to score as many points as possible.

In the first round, they received 15 points for every correct answer. But in the second round, the decision context changed: it no longer mattered if the answer was right or wrong. Instead, the score increased continuously from 0 to 45 degrees. The participants saw the same pairs in both rounds.

They ought really to have reached the same conclusion both times. This is because when we look at something, our retinas convert the reflected light into visual information that is transmitted to our brain via nerve pathways.

There, they are matched with our prior knowledge and experience and processed to provide a three-​dimensional image. The visual information was the same in both rounds.

When the researchers evaluated the experiment, they realized that the participants had adjusted their perceptions in the second round to score as many points as possible. If they actually saw the world objectively, there shouldn’t be any differences between the two rounds.

Participants’ assessments of the Gabor patches’ angles ought to have been the same each time, irrespective of the decision context. But this wasn’t the case: “People flexibly and unconsciously adjust their perceptions when it works to their advantage,” Polania said.

For Polania and his coauthors, inferring that cognitive distortions are errors that cause us to make inaccurate or irrational judgements and decisions is missing the point. “Since our cognitive abilities are limited, it actually makes sense that we perceive the world in a distorted or selective way,” he said.