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Why are some people unable to recognize familiar faces? What are the effects of brain injuries?
Face perception is an individual’s understanding and interpretation of faces. This perception implies the presence of consciousness and therefore rules out automated facial recognition systems. Although facial recognition occurs in other species, this article will focus on human face perception. The perception of facial features is an important part of social cognition. Information gained from faces helps people understand each other's identities, compare their thoughts, emotions, predict their behavior, recognize their emotions, establish connections, and communicate through body language. Therefore, developing facial recognition is a necessary cornerstone of complex social structures.
Having the ability to recognize identity, emotion, age, gender, and race allows people to shape how we interact with each other and make sense of our immediate surroundings.
Although face perception is thought to arise primarily from visual uptake, research shows that even people who are born blind can learn face perception without vision. There are currently several theories describing the process of face perception in adults, mainly derived from research on normal adult face perception and research on facial perception disorders caused by brain damage or neurological diseases.
Bruce & Young Model
One of the most widely accepted theories of face perception suggests that understanding faces involves several stages: from basic perceptual operations, to retrieving detailed information about the person (such as age, gender, or attractiveness), to being able to recall meaningful details, Such as their name and any relevant past experiences with that individual. This model, proposed by Vicki Bruce and Andrew Young in 1986, proposes that face perception involves independent sub-processes operating together.
Brain injuries and neurological disorders
After a brain injury, the face may become severely distorted. There are many kinds of distortions that occur - features may droop, swell, become discolored, and the position of the entire face relative to the head may change. This condition is called prosopometamorphopsia (PMO). In about half of the reported cases, the distortion is limited to the left or right side of the face. This form of PMO is called hemilateral PMO. Hemi-PMO is usually caused by lesions in the structures that connect the left and right hemispheres. Even in the other half of cases, bilateral facial features may appear distorted.
Research indicates that damage to certain brain regions can lead to specific deficits in people's ability to recognize faces, thereby helping to develop our understanding of normal facial perception.
Studying facial recognition disorders, such as one caused by brain damage, can be very helpful in understanding the workings of normal face perception. People with face recognition disorder may have differences in the way they understand faces, and research on these differences suggests the theory that there may be several stages. Brain imaging studies typically show significant activity in an area of the temporal lobe called the fusiform gyrus, which when damaged can lead to difficulties with facial recognition. This evidence drew special attention to this region, and it is sometimes called the "facial fusiform area" (FFA) because of its specificity in the recognition of unfamiliar faces.
Early development
Despite numerous studies, there is no universally accepted time frame for the human body to develop the ability to recognize faces. Many studies have found that infants focus preferentially on faces within their visual range, showing that they can recognize faces among other objects. Around three months after birth, infants show a particular interest in faces; however, this preference gradually disappears with age, reappears at the end of the first year, and then decreases again over the next two years.
In terms of emotion recognition, seven-month-old babies are able to distinguish facial emotions. However, it is unclear whether they fully develop the ability to recognize emotions. For seven-month-old babies, understanding the importance of facial expression displays is part of their social interactions.
Neuroanatomy of facial knowledge
Face perception has neuroanatomical correlates in the brain. The main areas include the "fusiform face area" located in the lateral brain, which is involved in the overall processing of faces and activities related to face recognition.
Facial knowledge is not determined by just one area, but by a complex network of multiple brain areas working together.
These face processing-related regions showed higher activation levels in the perception task of different face frames, relative to other visual perception tasks, emphasizing the specialized role of these regions in face recognition.
Psychological Neuroscience
With a deeper understanding of human facial recognition capabilities, scientists are also exploring how the brain processes facial information through various neural mechanisms when studying different aspects of facial perception. How this complex perceptual process is affected in different situations is undoubtedly an important topic for future research.
Many people may be thinking, what impact will impairment of face perception have on our social relationships?
