Sometimes the subject can recall the name when given clues. Sufferers are often frustrated when they know they know the name, but cannot produce it.
"hold on, I should know the name of that thing... give me a minute ..."
Sometimes subjects may know what to do with an object, but still not be able to give a name to the object. For example, show a subject an orange, and ask what it's called. The same subject may be well aware that the object can be peeled and eaten, and may be able to demonstrate this by actions or even verbal responses.
This type of phenomenon can be quite complex, and usually involves a breakdown in one or more pathways between regions in the brain. The responses may also differ depending on whether objects are shown in the right or left hand side of the visual field.
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