They carried out a series of experiments to find out how people detect objects under different conditions. They suggest that the brain’s representation of an object includes how someone perceives it — not just how it truly is. They conclude that a person cannot see an object in a way that is entirely separate from their point of view.
Their findings challenge previous assumptions in the philosophy, psychology, and neuroscience of perception and appear in the journal PNAS.
A person’s perception of the world around them is a complex process that goes far beyond wavelengths of light hitting the back of the eye. It involves multipart transformations by the brain and is biased by what we a person has seen previously and what they know to be true about the world.
The way a person perceives things depends on their perspective, their point of view. What happens when perspective distorts an object’s form is the subject of a long-standing philosophical debate. As the paper puts it, do we ever escape the perspective from which we view the world?
“This question about the influence of one’s own perspective on perception is one [that] philosophers have been discussing for centuries,” says senior author Chaz Firestone, assistant professor of Psychological and Brain Sciences and Director of the Perception & Mind Lab.
Firestone and his team are investigating whether the brain represents an object based on how a person sees it (their perspective) and influences this perception, even when the person knows that the true form of the object is different.
To test this idea experimentally, the researchers conducted nine separate experiments, the first seven involving computer-generated objects and the final two using real-world objects viewed under natural conditions.
Most of the experiments featured coins that were either circular shown head-on (immediately recognizable as a circle), oval shown head-on (immediately recognizable as an oval), or a circular coin rotated in such a way that it appeared similar to the oval coin.
In the first experiment, researchers showed the participants a series of images and asked them to determine which showed the oval coin. An oval coin presented head-on was present in all images, and a circular coin appeared either head-on or turned 45 degrees.
Further experiments involved coins of different sizes, rotations, the number of coins, and the movement of the coins. Other experiments included variations on this theme using different shapes.
In the final experiments, the participants sat in front of a real-life display containing wooden coins, and the researchers asked them to indicate the location of the oval coin.
The results showed that when the researchers presented the participants with tilted, circular coins at the same time as the oval coins, their response times slowed significantly. This was the case whether the coins were still or moving and whether the volunteers saw them on a computer screen or in real life.
The fact that the subjects were distracted by the tilted circles suggests that their brains did represent the tilted coin as oval in shape, rather than as the circular object it is in reality. All of the experiments generated results consistent with this idea.
The results indicate that people cannot separate an object’s true identity from how they see it.
“Our subjective approach to the world stays with us,” says lead author Jorge Morales, postdoctoral fellow and resident philosopher in the Perception & Mind Lab. “Even when we try to perceive the world the way it really is, we can’t completely discard our perspective.”
This study also shows that researchers can test ideas from philosophy empirically, and is the first of several experiments the lab is working on to understand human perception better.
