People with prosopagnosia have great difficulty recognizing faces, and may fail to recognize people that they have met many times and know well – even family members and close friends. This is quite different from forgetting names (which is very common). Prosopagnosia has nothing to do with how hard one tries to remember faces. It is caused by a problem with processing visual information in the brain, which can be present at birth or develop later due to brain injury.
People with prosopagnosia become very good at using clues such as context, clothes, or voice to work out who people are. So people with prosopagnosia may seem to recognise you one day, and then ignore you completely another day when they meet you unexpectedly, or you change your hairstyle. Between one and two people in every hundred may have some degree of prosopagnosia.
Many people get upset or angry if someone they know does not recognize them or say hello - they think that the person who does this is rude, self-obsessed, or is ignoring them. People with prosopagnosia risk doing this many times every day, often without even knowing they have done it. This can make mixing with friends and colleagues very stressful and embarrassing, causing strained relationships.
You can make things much easier for someone with prosopagnosia by simply saying who you are! If you are with a group of friends and colleagues you may sometimes also be able to help out by quietly saying who other people in the group are.
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