This is A.N., she’s a 23 year old woman from Georgia.
A.N. is healthy by all means, but she can’t figure out who is calling her when she answers
her phone.
And she can’t tell when her favourite singer comes on the radio.
She can tell people’s faces apart, but if you asked her to imagine what a certain celebrity
or Kermit the Frog sounds like… she couldn’t.
The story of A.N. is just one example of Phonagnosia, a condition where people are unable to recognise
or imagine familiar voices.
It comes from “phone”, the Ancient Greek word for voice and “agnosia”, a loss of
knowledge.
So…
Why can you tell voices apart?
Usually a few of our senses work together to identify people.
For example, our vision and hearing team up to say “Hey!
That’s Mario!”
Researchers looked into how this works in a 2006 study, where one group of people was
exposed to pairs of voices and faces, and the other group was exposed to pairs of voices
and names.
Then the researchers mixed everything up and asked one group to match the voices back to
the faces and the other group to match the voices back to the names.
The group that was exposed to pairs of voices and faces were faster at identifying the voices
- they had more sensory information to work with.
Still, people in both groups showed an increase in brain activity in specific areas.
They were all able to distinguish voices, and we do know this is tied to our ability
to decipher language.
In another study scientists found people with dyslexia had difficulty telling voices apart.
They had an impaired ability to organise those little parts of language compared to those
without dyslexia.
But this effect is only in their native language.
Once voices speaking foreign languages were introduced, everyone was bad at recognizing
voices.
So the people in both of these studies could distinguish different voices, but recognising
voices, as in, from those people you already know, is a separate ability.
And there’s lots of things that contribute to our ability to identify a speaker, whether
we know them or not.
Things like accent, cadence, intonation, key, phrasing, pitch, and stress patterns.
You use these characteristics of speech to build a “picture” of what someone’s
voice is like - just like you do with their facial characteristics.
And your ability to recognise faces is actually linked to your ability to recognise voices.
The Fusiform Facial Area is a specialised area of your brain that you use to recognise
faces, and it’s connected to part of your auditory cortex in three places.
These three places all respond to human voices and are active when we attempt to identify
voices.
This response is researchers best guess in the search to find the exact mechanism of
voice recognition.
From an evolutionary perspective, identifying both voices and faces allows us to function
as part of a social group.
Not everyone needs to comprehend language to recognize different human voices, though.
When elephants were played recordings of voices speaking in two different languages, they
reacted defensively to the language associated with locals who clashed with the elephants.
Tamed horses can also distinguish and recognize human voices, as can dogs, cats and crows.
In the case of A.N., her phonagnosia Is pretty rare.
She couldn't store or retrieve those bundles of information that allow us to identify a
voice — you know, accent, cadence, intonation, key, phrasing, pitch, and stress patterns.
Our ability to recognise voices is one of those amazing things our brain does when we're
on autopilot.
When you take a moment to stop and think about it, it's pretty fly.
And hear me out...
Let me know if you can figure out which of my friends’ voices you heard in this video.
You know, if they struck a vocal chord.
I’ll stop now.