"The groundwork of all happiness is health." - Leigh Hunt

Do you hear what I see? How blindness changes the way you process the sound of movement.

There is nearly nothing on this planet. Small children run into the lounge. Cars zip by on the road. Motion is some of the. Important features in the environment; The ability to predict the movement of objects on this planet is usually directly related to survival – whether it's a gazelle detecting the slow motion of a tiger or a driver merging into 4 lanes of traffic.

Motion is so necessary that the primate brain developed a dedicated system for processing visual motion, called the medial temporal cortex. 50 million years ago. This area of ​​the brain accommodates neurons specialized for detecting moving objects. This Motion detectors Compute the data needed to trace objects as they repeatedly change their location over time, then send signals in regards to the moving world to other regions of the brain, reminiscent of those involved in planning muscle movements. Is.

The medial temporal cortex is involved within the processing of visual motion.
Gray, vectorized by mysid, colored by was_a_bee/Wikimedia Commons

It's easy to grasp that you just see and listen to movement the identical way. However, how the brain processes auditory motion. Open scientific question For at the least 30 years. This debate centers on two theories: one supports the existence of specialised auditory motion detectors just like visual motion, and the opposite suggests that folks hear object motion as discrete snapshots.

As Computational Neuroscientistswe were intrigued after we saw a blind woman confidently crossing a busy intersection. Our laboratory has spent the past 20 years examining where auditory motion is represented within the brain of blind people.

Crossing a busy street based on hearing alone is an unattainable task for sighted people, as their brains Trust the vision To understand where things are. As anyone who has tried to search out a beeping cellular phone dropped behind a couch knows, sighted people have a really limited ability to infer the placement or movement of objects based on auditory information.

Yet individuals who develop into blind are capable of sense the moving world using only sound. How do people hear motion, and the way does being blind change this?

Aerial view of pedestrians at crosswalk, a few cars waiting on edge.
People who're blind are higher capable of track auditory motion in noisy situations than sighted people.
Orbon Alija/E+ via Getty Images

Crossing a busy street by voice alone

In our A recently published study In the journal PNAS, we tackled the query of how blind people hear motion by asking a rather different version: Are blind people higher at perceiving auditory motion? And if that's the case, why?

To answer this query, we used a sure bet where we asked study participants to guage the direction of a sound moving left or right. This moving sound was embedded in bursts of stationary background noise just like radio static that were randomly placed in space and time.

Our first query was whether blind participants would perform higher on the duty. We measured how loud the auditory motion needed to be for participants to perform the duty accurately 65% ​​of the time. We found that blind participants' hearing didn't differ from sighted participants. However, blind participants were capable of determine the direction of the auditory movement. Very quiet levels More than sighted participants. In other words, individuals who became blind early in life are higher at hearing the auditory movement of objects in a loud world.

Showing the movement of an object from one corner of the plane to another, where the blind participant can detect the position of the object more closely than the sighted participant.
Blind participants were capable of determine the position of the item because it moved and stopped more closely than sighted participants.
Ione Fine and Woon Ju Park, CC BY-NC-ND

We then examined how noise bursts interfered with the power to inform the direction of movement. For each sighted and blind participants, only noise bursts in the beginning and end of every trial affected performance. These results show that folks don't repeatedly track objects using sound: as a substitute they infer auditory motion. The position of their beginning and ending soundsis more consistent with the snapshot hypothesis.

Both the blind and the sighted inferred movement from the onset and stop of the sound. So why were blind people so a lot better at understanding auditory motion than sighted people?

Further evaluation of the consequences of background noise on the power to trace auditory motion showed that blind participants were only affected by noise bursts occurring at the identical time. Same places in space and moments in time As the onset and offset of moving sound. This means they were more sensitive to the start and end of the particular auditory movement and fewer sensitive to bursts of unrelated noise.

When you hear what I see.

As any parent of a blind child will inform you, understanding movement is advantageous. One of many ways That blind children learn to interact with the world using different gestures and actions.

A sighted child recognizes the face of its parent because it approaches the cradle, while a blind child recognizes the sound of their footsteps. A sighted toddler looks on the dog to get his parent's attention, while a blind toddler does Pull your parents' hand. In the direction of barking.

Understanding the potential of blind people Learn how to communicate successfully. Provides a novel appreciation of the extraordinary flexibility of the human mind with a world designed for the viewer.