Which term describes illogical and incomprehensible speech?

• A. Incoherence
• B. Blocking
• C. Perseveration
• D. Echolalia

Answer: (A)

Incoherence describes disorganized thought and speech in which ideas do not connect and the words are jumbled or nonsensical, making the message hard or impossible to understand. In a mental status exam, you’d see speech that cannot be followed because of abrupt derailment, illogical associations, or nonsensical phrases. For example, a patient might say something like, “The green idea swallows the thunder, because the clock tastes blue,” which lacks a logical connection between elements. This is different from blocking, where the flow of speech stops abruptly; perseveration, where a single idea or word is repetitively repeated; and echolalia, where a person just repeats someone else’s words. Incoherence signals a breakdown in the form of thought often seen in acute psychosis, delirium, or severe mood disorders, reflecting a disruption in how thoughts are organized into language.