An impoverishment in thinking that is inferred from observing speech and language behavior.
There may be brief and concrete replies to questions and restriction in the amount of spontaneous speech (termed: poverty of speech). Sometimes the speech is adequate in amount but conveys little information because it is overly concrete, overly abstract, repetitive, or stereotyped (termed: poverty of content).

Adapted from American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 5th ed. Washington, DC. American Psychiatric Association. 2013. Page 817.