You stop at a shop window and wonder why someone inside is blatantly staring at you, until you realize this person is you. Scenarios like this are impossible for us to imagine, but quite common for sufferers of acquired prosopagnosia (AP), a condition which can occur after brain damage, hindering the ability to recognise faces. In a new study, researchers have found that the condition is linked to an inability to process faces as a whole, or holistically.
Researchers from the Université de Louvain in Belgium have been investigating the case of a 59 year-old kindergarten teacher, one of the few cases of pure acquired prosopagnosia in the world. She has been suffering from AP since a closed head injury in 1992. Past records show that these patients have difficulty in processing the eye-region of a face, or perceiving relative distances between facial features. However, in their new study, the researchers found that both impairments are linked to a common cause - the inability to process faces as a whole.
The participants in the study were asked to match images of faces, which had been manipulated to differ either in a single feature or the distance between two features. As expected, the patient had difficulty in the matching task when changes to the faces occurred randomly. Strikingly, however, when told which feature had been changed (e.g. distance between the eyes), the patient's performance was similar to that of healthy subjects.
The findings suggest that AP patients are unable to process different elements of the face in parallel and instead they apply a locally restricted, serial processing style, which is particularly inefficient for certain types of information. Knowing which information to look for makes this strategy relatively more efficient.
Though these findings may not really help AP patients in real-life situations, it does shed light on what makes normal face recognition so overwhelmingly efficient. Our capacity to simultaneously integrate the multiple facial elements into a unique representation is incredible, the scientists note.
|
