In our recent study published in PNAS, we show that people who come blind early in life are much better at hearing object motion than those who are sighted. They do this by more accurately detecting when and where the sound begins or ends. Read more about it in The Conversation.
Big picture: Imagine yourself trying to cross a busy street with your eyes closed. You will likely use your ears to hear if the cars are moving or not. This is because audition is the only sense that can provide information about distant space other than vision. Still, it probably will feel like an impossible task — Your brain is “wired” to rely on vision to figure out where things are.
- In fact, in parts of the brain that help you ‘see’ the world, there is a dedicated area for processing visual motion. The neurons in this area continuously track objects as they smoothly change their position over time.
- In contrast, sighted people have very limited abilities to precisely localize where the sound is coming from.
Our question: Yet, early blind individuals are able to navigate this seemingly ‘visual’ world using only sound. How does early blindness affect our abilities to hear auditory motion?
- What we did: Sighted and early blind individuals participated in a simple task where they judged the direction of a moving object. Here, we embedded the target object in loud background noise, making the task harder.
What we found: Early blind individuals were so much more sensitive at hearing object motion! Early blind individuals had similar hearing abilities as sighted (i.e., they would perform similarly at an audiologist visit). But they could tell the direction of moving sounds even when the object moved at much quieter levels.
- Go deeper: Both sighted and early blind individuals did this task by taking snapshots of sound objects at their onsets and offsets (which is different from vision). However, early blind individuals’ snapshots were more accurate.