What did Jakobson learn about speech through metaphoric and metonymic aphasia? What is it like to have problems in the metaphoric, metonymic, syntagmatic and paradigmatic axes?

Through his study of aphasia, Jakobsen was able to find evidence to support his theory that language involves two “modes of arrangement,” including combination and selection. In normal speech mechanics, both metaphoric selection and metonymic combination are used fluently. In aphasic speech, either metaphoric or metonymic are blocked. In some cases, an aphasic person may lack both metonymic and metaphoric abilities.
When someone suffers from metaphoric aphasia, or similarity disorder, as Jakobsen puts it, they are still able to create units of speech and continue to make use of metonymic links. However, the disorder becomes pronounced when the affected person attempts to make substitutions for similar phrases. Someone with metonymic aphasia might be unable to substitute synonymous words and terms. These aphasics tend to be incapable of identifying objects with names and instead describe their function. For example, a metaphoric aphasic might describe a knife as an object that is used to cut without being able to identify it with the word knife. Knife, as a concept, holds no inherent meaning to the metaphoric aphasic.
Metonymic aphasia, also known as a spectrum of contiguity disorders, presents itself in the form of an inability to combine smaller units of language into complex units. It is the opposite of metaphoric aphasia, but the two commonly present together. A person with metonymic aphasia does not have the ability to organize words into more complex structures, making it difficult for these aphasics to use words that depend strongly on the context of the surrounding sentence. For this reason, those with metonymic aphasia tend to use one-word phrases.
Syntagmatic aphasia is related to contiguities, while paradigmatic aphasia is related to similarities. Someone with paradigmatic aphasia has difficult replacing or substituting words and depends upon the literal definitions, while someone with syntagmatic aphasia has difficulty combining thoughts into larger phrases.
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