People who can no longer recognize faces compensate with heightened voice recognition abilities, says a York University study, which also finds that our brains may identify people and things on separate neurological planes.
The study, recently published in the journal Neuropsychologia looked at a rare disorder called prosopagnosia, in which the ability to visually identify faces is lost or severely impaired.
Researchers performed a series of experiments that gauged prosopagnosia sufferers’ recognition of faces, objects and voices and other sounds, both separately and in varying combinations; the scientists compared these results to those of control subjects with normal brain functioning.
“We were interested in investigating the interactions between different types of sensory inputs,” says lead researcher Jennifer Steeves (left), a professor of psychology in York’s Faculty of Health. “For example, does seeing a person’s face and listening to them speaking at the same time offer more helpful information to identify that person, or is a single sensory input superior?”
Steeves’ experiments involved a patient who suffered brain damage from meningitis as a child. With extensive lesions on the right hemisphere and most of the ventral visual areas, he was unable to recognize familiar faces, facial expressions, objects, colours or words.
“Quite remarkably, even with these deficits, he was able to hold a job and maintain an independent lifestyle,” Steeves says. “We wanted to find out what cognitive functions were compensating to help him achieve this.”
In one experiment, participants were required to rapidly learn the identities of 10 individuals, using an image of a face paired with a voice.
Prior to this exercise, subjects were presented with grey-scale images of 110 female faces that had been stripped of distinguishing features. They were also fed auditory stimuli – a 20-second neutral passage spoken in English by one of 110 female voices. Participants were then tested on what they had learned in visual and auditory-only modes, and in combination.
Steeves and her colleagues found that control subjects relied more heavily on visual cues, while the patient with prosopagnosia used auditory information more expertly to recognize people. However, auditory cues didn’t help in identifying objects, leading researchers to believe that our processing of people and things occur in two different neurological pathways.
Untangling this web of sensory cues is important on more than one level, Steeves notes. “Our hope is that it will help not only our understanding of those with brain disorders, but also to understand how healthy brains function,” she says.
The study, “Superior voice recognition in a patient with acquired prosopagnosia and object agnosia,” is co-authored by Adria Hoover, a York psychology graduate student, and Jean-François Démonet, director of France’s Institut National de la Santé et de la Recherche Médicale (INSERM).
Steeves is one of the researchers based in York’s new state-of-the-art Sherman Health Science Research Centre, which officially opened on Sept. 14. She leads the Perceptual Neuroscience Laboratory, which is based on the building’s main level.
The research was funded by the Natural Sciences & Engineering Research Council of Canada and France’s Ministry of Foreign Affairs.