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Researchers have learned much about the cognitive organization of the language system by studying speech errors made by speakers with and without aphasia. Some aspects of errors made in language production reflect linguistic properties of language (e.g., linguistic similarities between an intended word and the word that was produced in error). Other aspects reflect processes that enable production of language (e.g., substitutions or sequencing errors). A particularly intriguing class of error is perseveration, the unintended retrieval of words or sounds after they have been recently produced. Although the occurrence of perseverations is influenced by both linguistic and processing aspects of language production, these errors have been particularly instructive about the latter aspect. Martin and Dell (2007) proposed that word and sound perseverations result from the same mechanisms as non-perseverative substitutions: slowed activation of the intended utterance and linguistic similarity between the target and error. They differ from non-perseverative substitutions in their probability of occurrence, which is increased by residual activation following their recent production. In this article, I will review this account of perseverations and discuss its implications for treatment approaches to reduce perseverations.

Providing language therapy to a person with aphasia (PWA) who exhibits a moderate to severe tendency to perseverate is one of the most difficult challenges with which a language therapist can be confronted. In the case of severe verbal perseveration, systematic language therapy may not even be possible. Thus, in such cases, to reduce or eliminate perseveration, the clinician needs to understand the mechanisms underlying verbal perseveration in the overall context of the individual's language impairment.

Under the premise that verbal perseveration reflects the primary language impairment, for example, and affects the retrieval of phonemes or word retrieval, the clinician will need to choose different therapy strategies for each PWA. Following a summary of general suggestions put forward in the aphasia literature for reducing perseveration, I will discuss available protocols for treating perseveration (e.g., Treatment of Aphasic Perseveration or TAP; Helm-Estabrooks, Emery, & Albert, 1987) and survey the publications on treatment of verbal perseveration.

Client MV's sister: ... "I think I have to take my sister to the heart specialist. In the past weeks she has behaved a little differently and I am worried that she is having problems breathing. When I am having a conversation with her and she has problems speaking [i.e., the client gets stuck on a word she has previously produced or perseverates], all of a sudden she just stops talking and she takes a deep breath! Then slowly she starts talking again."

Therapist: "No, Dr ... ., you don't have to go to the heart specialist with your sister. She doesn't have any problems breathing. Your sister is just following my advice. I told her, that when she notices that she is having a problem finding the name of something or she says a word she has just produced, that she should stop talking and take a long deep breath. She should take a break and then slowly start all over again. Apparently she is really following my suggestion! I am really glad to hear that."

Client MV's sister: "Oh, I am so relieved to hear that. I was worried about her! Come to think of it, after she takes a deep breath, she usually says the right word or something close to it!"

(Excerpts from a telephone conversation between a person with aphasia's [PWA's] therapist and the client's sister, translated from German.)

Perseveration, and in particular verbal perseveration, has been defined in various ways depending on the perspective of the investigator. A widely accepted definition is that perseveration is the inappropriate recurrence or uncontrolled repetition of a previously produced response—phoneme, word, syntactic structure, semantic feature, idea, and the like—in place of the correct target item.

Verbal perseveration has a long history in aphasiology research. Reading the classical papers on the topic is essential to gaining a basic understanding of perseverative language behavior. A survey of the classical literature on perseveration reveals three explanations of the nature of the underlying deficit that results in perseveration. It will be shown that many current concepts were actually posited in the classical aphasiology publications as early as 1879.

A very nice illustration to this topic was provided by a paralytic patient of Abraham, whom I observed together with him. He had almost colossal perseveration. Instead of all the requested words to be written down, once he produced the word "tongue" (= "Zunge"), which he also produced in response to any other word to be repeated. When I wrote down a 3 in front of him with the request for him to copy it, he added to my 3 ‘unge’ making it Zunge (as he considered my 3 to be a Z, which of course in writing is similar to Z in German). One sees here clearly, that not the movement itself got stuck, but rather the inner word form. (Liepmann, 1905, pp. 120–121)

The purpose of this study was to measure outcomes resulting from a treatment designed to reduce aphasic perseverations by decreasing activation of the perseverative response and increasing activation of the target response. A single-subject design was used. A Spanish-speaking male with moderate-to-severe receptive-expressive aphasia participated in this study. Treatment involved the use of systematic reduction of interstimulus interval paired with semantic feature analysis. The treatment resulted in a decrease in perseveration, but only minor increases in naming accuracy on trained and untrained stimuli. In addition, an increase in overall verbal output was observed. Decreased perseveration was maintained during follow-up. Outcomes suggest the treatment successfully reduces perseveration and increases verbal output. Additional research is needed to evaluate the effectiveness of this treatment.