The Effects of Temporal and Semantic Conditions on the Occurrence of the Error Response of Perseveration in Adult Aphasics

Abstract

This study sought to determine whether the incidence of perseveration in the responses of adult aphasics could be affected by altering stimulus factors such as semantic difficulty and the rate of presentation of stimuli. Thirty-one aphasic men supplied 1-word responses within three randomly arranged language tasks: sentence completion, picture naming, and word reading. Within each task subjects received stimuli from two 20-word lists of words contrasted for their frequency of occurrence in the language. Each list was presented once with 1-sec intervals between subjects' responses and subsequent stimuli, and once with 10-sec intervals. Results indicated that when semantic difficulty as measured by the frequency of occurrence of the single-word responses was reduced, the mean number of perseverations decreased significantly. When time intervals were increased from 1 to 10 seconds, perseverations decreased significantly. Sentence completion and picture naming elicited significantly more perseverations than word reading. Perseveration and other verbal errors were similarly affected by the variable of semantic difficulty, but only perseverative errors were significantly reduced when time intervals were increased. Word length, presentation order of tasks and conditions, and time postonset of aphasia appeared to have little relationship to perseveration.

Mechanisms underlying perseveration in aphasia: evidence from a single case study

“…If one assumes that low frequency words have weaker corresponding input, they should elicit a greater number of perseverations than high frequency words because it will be harder for them to override persistently active representations. While there has been some support for this in previous studies [30,64], frequency has yet to be directly manipulated in a single case study of perseveration. (2) Presentation rate can be thought of as a factor that influences the activity levels of persistent representations.…”

“…Perseverations should, therefore, also be more likely under a fast presentation rate with shorter delays between stimuli because heightened persistent activity will be more difficult to override. There has also been some support for this prediction in a large group study of aphasic patients [64], but it has yet to be tested in a more detailed single case study. (3) Repetition can be thought of as another factor that increases the activity levels of persistent representations.…”

“…Perhaps the most striking of these is that a previous response may be provided again after a number of intervening stimuli or responses [2,12,30,37,64]. The often delayed nature of these perseverations has led some researchers to refer to them as recurrent, distinguishing them from types that appear to be an extension or continuation of the immediately preceding response [62,63].…”

“…However, they do appear to decrease in likelihood as the number of intervening trials increases and are most common after little or no delay [12]. Recurrent perseverations may be on whole words, part words or even parts of drawings, sometimes occurring as a blend of a previous response and the current target [1,6,12,53,64,65]. Individual aphasic patients may perseverate on more than one task, although some patients appear to perseverate only on certain tasks [12,14,53].…”

“…Only word length was found to have a significant effect with more perseverations produced to longer target words. Santo Pietro and Rigrodsky [64] found that in sentence completion, picture naming and word-reading tasks, aphasics produced more perseverations to stimuli of low lexical frequency and when a fast presentation rate was used compared to a slower rate (response-stimulus interval (RSI) of 1 s versus 10 s). A few researchers have suggested that perseverations often share a phonological or semantic relationship with the stimuli that elicit them [1,37,65].…”