For me, caller ID is one of the best inventions of all time. Before it became mainstream, I dreaded picking up the phone. A lot of times, I couldn’t recognize the person on the other side by just hearing his or her voice, and so I was often subjected to a slew of jokes and mockery and puzzle-solving.
It turns out I was hardly alone in my misery. An inability to identify people by their voices is a poorly understood deficit called phonagnosia ― a term coming from “phone,” meaning “voice” in Ancient Greek, and “agnosia,” meaning a “loss of knowledge.”
And the condition might be much more prevalent than we thought, according to a new study published in the August issue of Brain and Language.
“There are some people, our survey showed about 3.2 percent, who have great difficulty in recognizing others by their voices,” said Irving Biederman, a professor of neuroscience at the University of Southern California.
Biederman and his colleague Bryan Shilowich tested 730 people’s ability to correctly identify voices of celebrities who they were familiar with. Assuming that people are on a spectrum in their ability to recognize voices, researchers expected the scores to have a normal distribution and fall on a bell-shape curve. But the results showed an unusual bump at the very low end of the spectrum.
In other words, more people than researchers expected were really bad at recognizing voices.
“We would have expected eight people to score that low. But there were 23,” Biederman said. This suggests that there’s a group of people whose low performance in voice-recognition falls outside of what is considered normal.
Realizing Everyone Recognizes Voices ... And You Don’t
A few years ago, one of Biederman’s students approached him to talk about her problem with voice recognition. The woman, identified as AN, had discovered only at age 18 that other people could recognize their friends or familiar actors and singers by just hearing them. To AN, this was news.
“I never really noticed a deficit when I was younger because I never really thought about people being ABLE to easily recognize voices without seeing the person with which they were conversing. When I could tell who was on the phone, it would be from inference,” she told the researchers.
Biederman and his colleagues ran a couple of tests on AN. Her case, a well-documented report of phonagnosia in an otherwise healthy person, was published last year.
The study suggested that AN didn’t have a perceptual problem with voices. She could hear them just fine and grasp the differences, but she couldn’t put a face on them. In one of the experiments, for example, the researchers asked AN and 21 control participants to identify the voices of celebrities, including actors and politicians that AN had heard speaking. She did much worse at identifying the voices than the controls.
The Mind’s Ear
People with phonagnosia also can’t imagine familiar voices. When they are asked to think of someone’s voice, their mind’s ear remains essentially silent.
In the new survey, 18 of the 23 people who scored the lowest on the voice recognition test said they couldn’t imagine the voices of celebrities they knew.
Biederman did a little demo test on me:
“Are you familiar with Morgan Freeman?” he asked me.
“Can you imagine his voice?”
“No. But I can think of facts about his voice. I know he has a deep voice.”
I was clearly seeing a Morgan Freeman in my mind’s eye, with silver curly hair and short beard, earrings and freckles. But his voice wasn’t coming to me.
“Can you imagine the sound of breaking glass?”
“The sounds of rushing water?”
“What we found was that people with phonagnosia have no difficulty in imagining the sounds made by objects or animal sounds like a bird singing. But they can’t imagine the voice of people they know.”
I was still able to imagine the sound of people extremely close to me, like my parents and some of my friends. Many of those with phonagnosia that Biederman has seen can’t even do that.
When examining AN, the researchers looked at brain activity (with fMRI brain scans) as AN and people without the condition tried to imagine voices of celebrities.
“People without the condition showed high activity in the ventromedial prefrontal cortex when they were imagining voices, but she showed nothing,” Biederman said.
Phonagnosia is similar to another odd condition known as prosopagnosia, or face blindness. People with that condition have no difficulty in seeing a face, perceiving its differences from other faces, noticing peculiar features or judging the attractiveness of a face. But they are unable to recognize or imagine the faces of familiar people.
Face blindness can occur if the part of the brain in charge of processing faces, known as the Fusiform Face Area, is damaged due to injury or stroke. But people can also be born face blind. It’s estimated that 2 percent of people have the condition.
Similarly, phonagnosia has been reported in both people with a history of neurological brain injury and people without it, such as the case of AN.
Interestingly, the two conditions don’t seem to overlap. People with phonagnosia show no problem in face recognition and vice-versa. AN, for example, tested even better than average when she had to identify familiar faces, Biederman said.
Scientists have studied other people with phonagnosia. In one case report published in 2014, researchers in Germany described two healthy academics, a man and a woman, both 32, who performed significantly worse than their peers in learning new voices, judging the familiarity of famous voices and discriminating pitch differences between voices. Both had normal hearing and showed no brain abnormalities. They were normal in any other test, from face recognition to musical abilities.
As cases like these show up more often scientific literature, it becomes more and more likely that developmental phonagnosia (as opposed to phonagnosia caused by brain injury) does indeed exist.
The next step is for researchers to find out where in the brain a voice connects to an identity. Biederman hopes future studies with a mix of brain imaging and direct recording of neurons may be able to answer that question. In the meantime, you can test your own voice recognition performance using this test.