Clanging refers specifically to behavior that is situationally inappropriate. While a poet rhyming is not evidence of mental illness, disorganized speech that impedes the patient's ability to communicate is a disorder in itself, often seen in schizophrenia.
^Peralta, Victor; Cuesta, Manuel J.; de Leon, Jose (March 1992). "Formal thought disorder in schizophrenia: A factor analytic study". Comprehensive Psychiatry33 (2): 105–110. doi:10.1016/0010-440X(92)90005-B. PMID1544294.
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