Use of eyesight impairs listening capabilities


Many students claim to be masters at multitasking, whether it involves talking on the phone and driving or texting during a lecture. However, recent scientific research actively refutes this notion. A new study in cognitive psychology finds that while concentrating on a task that requires the use of sight, our hearing capabilities are significantly impaired.

The study was conducted by Jerker Ronnberg, a professor of psychology with a focus on disability research, and his colleagues at Linkoping University in Sweden. The researchers asked 32 students to conduct visual tasks while taking images of their brain with an fMRI, or Functional Magnetic Resonance Imaging, camera.

It is a procedure that uses MRI technology in order to measure the brain’s activity by detecting changes in blood flow. The experimental design included three conditions: one condition without a visual task that had an active listening component, one condition with a task involving low visual demand and one condition involving a task with a high visual demand. The visual tasks were presented with a sound, but the participants were asked to ignore the sound.

In the first condition, the participants were asked to listen to a sound sequence while focusing on a fixed point on the screen. The participants were then asked to move their right index finger with the changes of the frequency in tone.

In the second condition, a visual task was presented to the participants. The visual task included a working memory test with a set of letters. In the third condition, the rigor of the memory test increased.

Participants completed these tasks in various conditions—some in calm and quiet environments, others in disruptive environments with a repetitive sound. Throughout the whole of the experiment, the participants were hooked up to an fMRI machine, which  the researchers used to take images of each participant’s brain activity. The researchers were particularly interested in what happens inside of the brain as it is engaged in a visual task, as well as how visual concentration changes when background noise increases.

“The brain is really clever, and helps us to concentrate on what we need to do. At the same time, it screens out distractions that are extraneous to the task. But the brain can’t cope with too many tasks: only one sense at a time can perform at its peak. This is why it’s not a good idea to talk on the phone while driving,” said Ronnberg.

The results of the study showed that brain activity in the auditory cortex functions perfectly, so long as we are subjected to sound alone. When the brain is given a visual task such as taking an exam, hearing is impaired as a result of a decreasing response by the nerves in the auditory cortex.

As the difficulty of the task increases, such as taking a more rigorous exam, the response of the nerves in the auditory cortex decrease even further. Visual tasks involving a high cognitive load significantly impair the brain’s response to sound—not only in the auditory cortex, but in the parts of the brain that deal with emotion as well.

The study asserts that the hearing capabilities of a person decrease as that person does a task that involves sight.