Perseveration, a term introduced by Neisser in 1895, refers to the inappropriate continuation or repetition of an earlier response after a change in task requirements. Although individuals without brain damage may display occasional perseverative behaviors (e.g., Ramage et al., 1999), as Allison (1966) pointed out, when perseveration is pronounced, “it is a reliable, if not a pathognomonic sign of disturbed brain function” (p. 1029). Indeed, perseveration has been described in association with a variety of neurological and psychiatric conditions, including stroke, head injury, dementia, Parkinson's disease, and schizophrenia.

Perseveration is such a notable and fascinating clinical phenomenon that for more than 100 years, various researchers have attempted to more precisely describe its characteristics, label its subtypes, and identify its neuropathological correlates and neuropsychological mechanisms. Good agreement has emerged from these studies as to the characteristics of various forms of perseveration, with rather little agreement as to labels for subtypes. And although most investigators agree that the frontal lobes and their associated white matter pathways play a prominent role in perseveration, other areas of the brain have been implicated. The neuropsychological mechanisms responsible for perseveration also are uncertain and probably vary according to subtypes. Among the mechanisms implicated are persistent memory traces, failure to inhibit prepotent responses, pathological inertia, and failure to disengage attention. For a review of some of this literature, see Hotz and Helm-Estabrooks (1995a).

It is important for professionals working with individuals having neurological conditions to be aware of perseveration and recognize its subtypes, because this behavior can contaminate experimental and clinical test results and reduce communicative effectiveness. Perseveration can occur in any behavioral output modality, including speech, writing, gesturing, drawing, and other forms of construction. Three primary forms of perseveration have been described, with one of these forms having four subtypes. The terms used here are derived from several sources (e.g., Santo-Pietro and Rigrodsky, 1986; Sandson and Albert, 1987; Lundgren et al., 1994; Hotz and Helm-Estabrooks, 1995b).

Stuck-in-set perseveration is the inappropriate maintenance of a category or framework of response after introduction of a new task. For example, as a part of a standardized test, an individual with traumatic brain injury without aphasia was asked to list as many animals as he could in 1 minute. He listed ten animals before he was given the following instructions: “Now I want you to name as many words as you can that start with the letter m. [He was shown a lowercase m.] Here are the rules. Do not name words that begin with a capital M. Do not say the same words with a different ending, like mop, then mopped or mopping. [The written letter m was removed.] Okay, you have 1 minute to name as many words you can think of that start with the letter m.” In response, the man said “monkey,” “mouse” in the first few seconds, then “man” after 15 seconds. He produced no further responses for the remaining time. Thus, although he understood the concept of listing m words, he could not disengage from the idea of listing animals, and his score for producing words according to a letter/sound category was contaminated by stuck-in-set perseveration.

Continuous perseveration is the inappropriate prolongation or continuation of a behavior without an intervening response or stimulus. For example, a woman with Alzheimer's disease was given the following spoken and written instructions: “Draw a clock. Put in all the numbers. Set the hands to 10 minutes after 11.” She wrote numbers 1 through 18 in the circle provided before she ran out of space. She then drew a hand to the number 10, but continued to draw hands to each number. Thus, either she was unable to disengage from the idea of drawing clock hands or she was unable to inhibit that particular graphomotor activity.

Recurrent perseveration is the inappropriate recurrence of a previous response following presentation of a new stimulus or after giving a different intervening response. For example, a man with fluent aphasia was asked to write the days of the week. He wrote, “Monday, Tuesday, Wednesday, Tuesday, Friday, Saturday, Monday, Sunday.”

Various subtypes of recurrent perseveration have been described and labeled. A primary distinction can be made between carryover of part of the phonemic structure of a previous word and repetition of an entire word.

An example of phonemic carryover perseveration, in which part of the phonemic makeup of a previous word is inappropriately repeated, is “comb” for comb, then “klower” for flower.

Within the category of whole-word carryover, three types of perseveration occur, semantic, lexical, and program-of-action perseveration.

Semantic perseverations are words that are semantically related to the target (e.g., repetition of the naming response apple when shown a lemon).

Lexical perseverations are words that have no obvious semantic relation to the target (e.g., repetition of the word key when asked to name scissors).

Program-of-action perseverations are repeated words that begin with the same initial sound as a previous response (e.g., repetition of the response wristwatch for subsequent objects, such as wrench, whose names begin with /r/).

Although, as mentioned earlier, perseveration occurs in association with many neurological and psychiatric conditions, perseverative behavior is especially notable in acquired aphasia. The results of their study of perseverative behaviors in aphasic individuals prompted Albert and Sandson (1986) to suggest that it “may even comprise an integral part of [the] specific language deficits in aphasia” (p. 105). This suggestion is supported by the work of other investigators (e.g., Santo-Pietro and Rigrodsky, 1982; Emery and Helm-Estabrooks, 1989; Helm-Estabrooks et al., 1998). There is good evidence that perseverative behaviors are unrelated to time post onset of aphasia but are correlated significantly with aphasia severity. Thus, perseveration can be a persistent problem for individuals with aphasia and interfere with all modalities of communicative expression. As such, perseveration is an important treatment target for speech and language clinicians working with aphasic individuals, although few approaches have been described thus far. Exceptions are the program designed by Helm-Estabrooks, Emery, and Albert (1987) to reduce verbal recurrent perseveration, and the strategies described by Bryant, Emery, and Helm-Estabrooks (1994) to manage various forms of perseveration in severe aphasia. See Helm-Estabrooks and Albert (2003) for updated descriptions on these methods.