Presence, completeness, and accuracy of main concepts in the connected speech of non-brain-damaged adults and adults with aphasia.

A standard rule-based system was used to evaluate the presence, accuracy, and completeness of main concepts in the connected speech of 20 non-brain-damaged adults and 20 adults with aphasia. Main concepts form a skeletal outline of the most important information (or "gist") in a message. The interjudge and intrajudge reliability of the main concept scoring system and the test-retest stability of scores were acceptable. The non-brain-damaged group produced significantly more Accurate/complete main concepts, and significantly fewer Accurate/incomplete, Inaccurate, and Absent main concepts than the group with aphasia. However, when the performance of individual subjects was evaluated, what best discriminated the performance of subjects with aphasia from that of non-brain-damaged subjects was not the number of main concepts they failed to mention but the accuracy and completeness of the main concepts they did produce. Measures of main concept production may be a clinically useful complement to other measures of communicative informativeness and efficiency.

Speech sample size and test-retest stability of connected speech measures for adults with aphasia.

The effect of speech sample size on the test-retest stability of two measures of connected speech--words per minute (WPM) and percent of words that are correct information units (Percent CIUs)--was evaluated. A standard set of 10 stimuli was used to elicit connected speech from 20 non-brain-damaged adults and 20 adults with aphasia. Each subject's responses to the 10 stimuli were transcribed and scored for WPM and Percent CIUs. Then each subject's responses to the 10 stimuli were randomly divided to produce smaller speech samples representing his or her responses to 1, 2, 3, 4, 5, and 7 stimuli. The test-retest stability of the WPM and Percent CIUs measures was then evaluated for each of the smaller sample sizes and for the complete 10-stimulus sample. For both groups, the test-retest stability of the two measures increased as sample size increased, with the greatest increases occurring as samples increased in size from those representing 1 stimulus to those representing 4 or 5 stimuli, with smaller increases in stability thereafter. In general, these results suggest that the best balance between high test-retest stability and the time and effort required to transcribe and score speech samples can be achieved with samples representing 4 or 5 stimuli (an average of 300 to 400 words for aphasic subjects), although this will vary across individuals.

A system for quantifying the informativeness and efficiency of the connected speech of adults with aphasia.

A standardized rule-based scoring system, the Correct Information Unit (CIU) analysis, was used to evaluate the informativeness and efficiency of the connected speech of 20 non-brain-damaged adults and 20 adults with aphasia in response to 10 elicitation stimuli. The interjudge reliability of the scoring system proved to be high, as did the session-to-session stability of performance on measures. There was a significant difference between the non-brain-damaged and aphasic speakers on each of the five measures derived from CIU and word counts. However, the three calculated measures (words per minute, percent CIUs, and CIUs per minute) more dependably separated aphasic from non-brain-damaged speakers on an individual basis than the two counts (number of words and number of CIUs).

Effects of apparent listener knowledge and picture stimuli on aphasic and non-brain-damaged speakers' narrative discourse.

This experiment investigated whether aphasic adults' assumptions regarding listener knowledge of the topic of discourse affects the content of their narrative discourse. Aphasic and non-brain-damaged adults told two stories about sequences of black-and-white line drawings in two conditions. In a knowledgeable listener condition, subjects told the stories to a listener while the subject and listener were looking at the pictures portraying the story. In a naive listener condition, subjects told the stories to a listener whom the subject had not met before, who did not have access to pictures about the stories, and who the subject was led to believe had no knowledge of the pictures upon which the stories were based. The differences in performance between non-brain-damaged and aphasic subjects were greater than the differences between listener conditions and between stories. Non-brain-damaged subjects produced significantly more words, more information, a greater percentage of words that communicated relevant and accurate information, and longer grammatical units than aphasic subjects did. There were no significant differences between non-brain-damaged and aphasic subjects in their use of four kinds of cohesive ties. Listener conditions and stories had few significant effects on non-brain-damaged or aphasic subjects' performance, and the few statistically significant effects that were observed did not appear to be clinically important.

Aphasic and non-brain-damaged adults' descriptions of aphasia test pictures and gender-biased pictures.

Twelve aphasic and 12 non-brain-damaged adult males described the speech elicitation pictures from the Boston Diagnostic Aphasia Examination (BDAE), the Minnesota Test for Differential Diagnosis of Aphasia (MTDDA), the Western Aphasia Battery (WAB), and six pictures representing male-biased or female-biased daily-life situations. For each speech sample we calculated number of words, words per minute, number of correct information units, percentage of words that were correct information units, and percentage of correct information units that were nouns or adjectives (amount of enumeration or naming). The WAB picture elicited more enumeration than the BDAE or MTDDA pictures, and information was produced at a slower rate in response to the WAB picture than the other two pictures. These differences were statistically significant and appear to be clinically important. Gender bias had statistically significant effects on two measures. Male-biased pictures elicited significantly more words and significantly more correct information units than female-biased pictures. However, these differences were small and do not appear to be clinically important. Two of the five measures (words per minute and percentage of words that were correct information units) differentiated non-brain-damaged speakers from aphasic speakers. The magnitude of these differences suggests that these measures provide clinically important information about the problems aphasic adults may have when they produce narrative discourse.

Aphasic and non-brain-damaged adults' knowledge of scripts for common situations.

This study was designed to determine whether script knowledge (mental representations of event sequences for situations that have been experienced in daily life) is compromised by aphasia. Aphasic and non-brain-damaged adults participated in several tasks designed to test their knowledge of scripts for common situations. The tasks included discrimination, in which subjects separated printed phrases identifying test scripts from phrases identifying foil scripts, centrality judgment, in which subjects identified the most typical and frequently occurring events in test scripts, and sequencing, in which subjects arranged the central events from test scripts in the order in which they would be expected to occur in the scripts. Error rates for both non-brain-damaged and aphasic subjects were low in all three tasks, and aphasic subjects generally performed as well as non-brain-damaged subjects did, except that aphasic subjects were significantly poorer at sequencing central events from scripts. However, the actual differences between groups in the sequencing task were quite small. These results suggest that knowledge of scripts is not seriously compromised by aphasia, at least when the aphasia is mild to moderate.

Comprehension of monologues and dialogues by aphasic listeners.

This study examined the frequently heard claim that aphasic listeners have more difficulty understanding speech in situations where there are multiple speakers than in situations where there is a single speaker. Nine stories about everyday events were written and videotaped as monologues, dialogues with one dominant speaker, and dialogues with both speakers contributing comparable amounts of information. Eighteen aphasic and 9 non-brain-damaged adults watched and listened to the videotapes. Listeners' comprehension and retention of the stories were tested by yes/no questions following each story. The three versions of the stories were understood and remembered equally well by aphasic and non-brain-damaged listeners, suggesting that listening to two speakers does not appreciably increase comprehension difficulty. These results suggest that factors other than the extent to which different speakers contribute to the topic of conversation are responsible for aphasic listeners' reported difficulties in comprehending multiple-speaker conversational interactions.

Referential communication by aphasic and nonaphasic adults.

Nonaphasic and nonfluent, mixed, and anomic aphasic adults participated in a referential communication task in which they described pictures to a nonaphasic listener so that the listener could point to the picture being described from an array of four. Both aphasic and nonaphasic subjects were able to determine what information was crucial for identifying pictures and communicate that information to a listener. The major differences between nonaphasic and aphasic subjects were in efficiency and accuracy of communication. Nonaphasic and nonfluent aphasic subjects were more efficient in communicating information than mixed or anomic aphasic subjects were. Nonfluent aphasic subjects were as efficient as nonaphasic speakers in this respect. Aphasic subjects communicated significantly more inaccurate information than nonaphasic speakers did. However, no more than 5% of the information communicated by aphasic subjects was inaccurate. Finally, aphasic speakers modified their descriptions in response to apparent communication failure in the same way that nonaphasic speakers did.

Error analysis and passage dependency of test items from a standardized test of multiple-sentence reading comprehension for aphasic and non-brain-damaged adults.

Aphasic and non-brain-damaged adults were tested with two forms of the Nelson Reading Skills Test (NRST; Hanna. Schell, & Schreiner, 1977). The NRST is a standardized measure of silent reading for students in Grades 3 through 9 and assesses comprehension of information at three levels of inference (literal, translational, and higher level). Subjects' responses to NRST test items were evaluated to determine if their performance differed on literal, translational, and higher level items. Subjects' performance was also evaluated to determine the passage dependency of NRST test items--the extent to which readers had to rely on information in the NRST reading passages to answer test items. Higher level NRST test items (requiring complex inferences) were significantly more difficult for both non-brain-damaged and aphasic adults than literal items (not requiring inferences) or translational items (requiring simple inferences). The passage dependency of NRST test items for aphasic readers was higher than those reported by Nicholas, MacLennan, and Brookshire (1986) for multiple-sentence reading tests designed for aphasic adults. This suggests that the NRST is a more valid measure of the multiple-sentence reading comprehension of aphasic adults than the other tests evaluated by Nicholas et al. (1986).

Story structure and retelling of narratives by aphasic and non-brain-damaged adults.

Aphasic and non-brain-damaged subjects listened to and retold two narrative stories three times in succession. Both aphasic and non-brain-damaged subjects were affected by story structure--they retold a greater proportion of information units that were central to the story structure than information units that were peripheral to the story structure. Both aphasic and non-brain-damaged subjects increased the amount of information retold across three retellings, although only the increases from Retelling 1 to Retelling 2 were statistically significant. Non-brain-damaged subjects consistently retold slightly more information units than aphasic subjects, but the differences were not statistically significant. In all three retellings, both groups of subjects retold information in the same order that it occurred in the stories.

Consistency of the effects of rate of speech on brain-damaged adults' comprehension of narrative discourse.

An experiment was carried out to assess the effects of slow and fast speech rate on comprehension of narrative discourse by aphasic, right-hemisphere-damaged, and non-brain-damaged adults. Aphasic subjects were divided into a high-comprehension group and a low-comprehension group based on their performance on the auditory comprehension subtests from the Boston Diagnostic Aphasia Examination. Subjects listened to 10 narrative stories. Half the stories were presented at slow speech rate (110-130 wpm) and half were presented at fast speech rate (190-210 wpm). After each story, subjects' comprehension and retention of stated and implied main ideas and details were tested. Brain-damaged subjects were tested twice, with at least 2 weeks intervening between sessions. Results demonstrated that salience had strong effects on comprehension for all groups of subjects--main ideas consistently were comprehended better than details. Directness affected subjects' comprehension of details, but not their comprehension of main ideas--stated details consistently were comprehended better than implied details. Non-brain-damaged subjects' comprehension was unaffected by differences in speech rate. Brain-damaged subjects comprehended details better in slow rate than in fast rate condition in the first test session, but the effects of rate on brain-damaged subjects' comprehension essentially disappeared by the second test. Furthermore, there were many instances in which individual subjects failed to demonstrate rate effects exhibited by their group.

Validity of multiple-sentence reading comprehension tests for aphasic adults.

This study assessed the passage dependency of multiple-sentence reading test items from the Boston Diagnostic Aphasia Examination (Goodglass & Kaplan, 1983), the Minnesota Test for Differential Diagnosis of Aphasia (Schuell, 1965), Examining for Aphasia (Eisenson, 1954), the Reading Comprehension Battery for Aphasia (LaPointe & Horner, 1979), and the Western Aphasia Battery (Kertesz, 1982). More than half of the test items from these reading tests were answered correctly by a significantly greater than chance number of both aphasic and non-brain-damaged adults without reading the passages whose comprehension the items purported to test. These results suggest that published tests for assessing aphasic persons' comprehension of multiple-sentence passages do not provide valid estimates of such persons' ability to comprehend information from printed texts.

Consistency of effects of slow rate and pauses on aphasic listeners' comprehension of spoken sentences.

The effects of intrasentence pauses and slow speaking rate on aphasic listeners' comprehension of spoken low- and high-difficulty sentences were investigated. Aphasic subjects heard commands spoken at a normal rate, at a slower than normal rate, and with inserted 4-s pauses. Subjects' performance was measured weekly for 4 consecutive weeks. The effects of pauses and slow rate on subjects' performance were not consistent across subjects or within subjects across sessions. Type of aphasia, time postonset of aphasia, and overall severity of comprehension deficit were not strongly related to aphasic listeners' responses to pauses or slow rate.

Comprehension of main ideas and details in coherent and noncoherent discourse by aphasic and nonaphasic listeners.

Aphasic and nonaphasic listeners' comprehension of main ideas and details within coherent and noncoherent narrative discourse was examined. Coherent paragraphs contained one topic to which all sentences in the paragraph related. Noncoherent paragraphs contained a change in topic with every third or fourth sentence. Each paragraph contained four main ideas and one or more details that related to each main idea. Listeners' responses to yes/no questions following each paragraph yielded the following results: (1) Nonaphasic listeners comprehended the paragraphs better than aphasic listeners. (2) Both aphasic and nonaphasic listeners comprehended main ideas better than they comprehended details. (3) Coherence did not affect comprehension of main ideas for either group. (4) Coherence did not affect comprehension of details by nonaphasic subjects. (5) Coherence affected comprehension of details by aphasic subjects, and their comprehension of details in coherent paragraphs was worse than their comprehension of details in noncoherent paragraphs. There was no significant correlation between Token Test scores and measures of paragraph comprehension.

Comprehension of directly and indirectly stated main ideas and details in discourse by brain-damaged and non-brain-damaged listeners.

Aphasic, right-hemisphere-damaged, and non-brain-damaged subjects heard short narrative paragraphs. Each paragraph contained four main ideas and one or more details related to each main idea. After each paragraph was presented, subjects' comprehension and retention of main ideas and details from the paragraph were tested. Some of the test items directly restated information from paragraphs and others paraphrased information from paragraphs. All groups of subjects remembered main ideas better than they remembered details, and no group of subjects was significantly affected by whether test items directly or indirectly stated information from paragraphs. Disfluent aphasic and right-hemisphere-damaged subjects' overall paragraphs comprehension scores were not significantly poorer than those of non-brain-damaged subjects. Fluent and mixed aphasic subjects' overall paragraph comprehension scores were significantly worse than those of non-brain-damaged and right-hemisphere-damaged subjects. Token Test and Boston Diagnostic Aphasia Examination auditory comprehension scores did not predict aphasic subjects' paragraph comprehension scores. right-hemisphere-damaged subjects' overall paragraph comprehension scores were not significantly those of non-brain-damaged and right-hemisphere-damaged subjects. Token Test and Boston Diagnostic Aphasia Examination auditory comprehension scores did not predict aphasic subjects' paragraph comprehension scores.

Verification of active and passive sentences by aphasic and nonaphasic subjects.

Aphasic and nonaphasic subjects participated in a sentence verification task in which they were asked to judge whether spoken sentences correctly described pictures presented with the sentences. True active and true passive sentences were presented, as well as, false active and passive sentences in which agents and objects were reversed. In addition, false active sentences in which either the subject, verb, or object did not match the picture were presented. Subjects' response accuracy and reaction times were recorded. Passive sentences were more difficult than active sentences for both groups of subjects, and false sentences were verified more quickly than true sentences for both groups. Both groups appeared to be processing sentences for meaning as they were received, rather than waiting for the entire sentence before beginning to process it for meaning. In general, performance of aphasic subjects resembled that of nonaphasic subjects, except that aphasic subjects consistently took longer to verify sentence meaning than nonaphasic subjects.