Posts Tagged ‘attention precedes eye movements’

How Your Eyes Betray Your Thoughts

July 18, 2019

This post is based on a book by Stefan Van Der Stigchel titled “How Attention Works: Finding Your Way in a World Full of Distraction.” Although we have two eyes, we are only able to fixate our gaze on one point in space at a time. The continuous movement of the eyes presents our visual system with interesting problems. If we were to see the actual images that fall on our retina, they would appear fuzzy and shaky because of the movements that the eyes make. Each individual eye movement is responsible for a separate part of the visual world falling on the retina. Yet we do not experience our visual world as a series of continuously shifting images, but rather as constant and fluid. We never become disoriented as a result of moving our eyes.

There is a difference between a retinal representation (the image that falls on the retina) and a spatiotopic representation (where the object is located in relation to our body). When we move our eyes to a different spot in space, the image that falls on our retina changes, but the world around us remains stable.

A similar updating process occurs in the case of memory. In order to know where we have already searched when we are looking for something, we need to remember those locations. When searching multiple locations the memory task become onerous. So it is useful to add some structure to our searching. If we always search our bookcase in the same manner there is no memory task and a strategy that guarantees search coverage. Searching in a haphazard is both inefficient and error prone as we are never able to recall all the individual locations that we have already searched.

There is an important difference between attention and eye movements. People are capable of shifting their attention without making any eye movements. This is useful when we find ourself talking to someone at a party but are actually more interested in someone else across the room. We are capable of looking our conversation partner in the eye while at the same time focusing our attention on the other person. The regions in our brain that are responsible for attention and eye movements overlap to a significant degree, and shifts in attention and eye movements co-occur in many situations. But we cannot make an eye movement without our attention first going to the end point of that movement. Attention precedes eye movements.

It is very important that our eye movements are made in the right direction to perform a task efficiently. Experts are good at developing strategies for their work, but they are often unaware of how they do what they do. This is similar to riding a bicycle: it is almost impossible to explain to a child how to ride a bike, because it doesn’t involve conscious competencies. But one can study how experts in different areas do their scanning.

It is very effective to show students what an expert looks at when he or she is scrutinizing a scan. This is true not only for radiologists, but also for all kinds of people who perform complicated tasks where looking at the right places is requires. Consider inspecting an airplane for mechanical faults before it departs on the next flight. Part of this job involves a visual check of the exterior of the airplane. When students are shown a view in which the most effective eye movements are projected on the screen, they learn faster and more effectively how to perform this kind of inspection. Eye-trackers are used to capture the performance of experts.