Imagine you are eating in a crowded cafe. Have you noticed that when you eat, you see very little that enters your visual field? For example, maybe you didn’t see the salt shaker on the table ahead. Quanta magazine recently said that we have filtering mechanisms that allow us to focus our attention on what is of interest.
Our brain filters the information it prioritizes, even if we are not aware of it. In these cases, our focus is not on a target but on specific characteristics of the stimuli, such as brightness or movement. This makes evolutionary sense, says neuroscientist Duje Tadin of the University of Rochester. “If there’s something moving in our field of view, that object is probably pretty important to our survival.”
Scientists have long known that our sensory processes should automatically scan for foreign objects. Otherwise we would not be able to experience the world as we live it. For example, when we look around us, our perceived field of vision remains fixed or moves smoothly with our gaze. But the eye also constantly makes small movements or twitches; our visual system has to automatically remove background vibration from our field of view.
This automatic background removal can also occur in surprising and unexpected ways. Consider an unusual finding made by Tadin and colleagues in 2003: We are good at detecting motion of small objects. But if these objects are simply magnified, we begin to have trouble perceiving their movement.
Recently at Nature Communications, Tadin’s team made a bold statement as to why: The brain prioritizes detection of objects that are more important to us and tend to be smaller. For a hawk looking for its food, a mouse jumping out of a field is more important than the swaying motion of the grass and trees around it. As a result, Tadin and his team discovered that the brain suppresses motion in the background of objects. As a side effect, they stated that we have more difficulty in perceiving the movements of larger objects. Because the brain looks at them as a kind of background.
The team also confirmed this idea with a training experiment in older adults. Other researchers have previously reported that there is not much difference between how well the elderly observe the movement of a small object and the movement of a larger object. That’s why Tadin and his colleagues predicted that older people would have trouble detecting small objects moving on a moving floor, and that’s exactly what they found. However, with a few weeks of training, the subjects became much better at recognizing this movement.
Yet, as the researchers discovered, the training did not actually improve the subjects’ ability to detect small moving objects. Measured alone, this skill did not change. Less distractions were behind their success. They got worse at detecting movements of larger background objects. “In a sense, their brains threw out information they could only process five weeks ago,” Tadin said. said.
What these results indicated was that our sensitivity to larger moving objects was lower. That’s because our brains tend to prioritize smaller moving objects against these backgrounds.
This is also the same strategy the brain uses in goal-directed attention processes. Our brains get rid of distracting or less useful information to highlight more relevant entries.
“Before attention can do its job, the brain already starts pruning a lot of information,” Tadin said. said. For motion detection, this pruning has to happen automatically as it has to be done very quickly. “Attention can do the same thing in much smarter and more flexible ways, but it’s not that effortless.”
As for how and what we perceive, Tadin says, “There’s a lot going on behind the scenes that we take for granted.” said.
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