Task-Specific Effects on Crosslinguistic Differences in Nouns and Verbs for Korean and English Speaking Individuals with Aphasia

Abstract

실어증은 뇌손상으로 인해 정상적으로 언어를 습득한 이후, 언어를 이해하거나 표현하는 영역과 관련하여 다양한 어려움을 보이는 언어장애를 말한다. 또한, 다양한 신경학적 손상을 동반하기도 하지만, 치매와 같은 비구어적 인지능력과 관련된 신경학적 손상은 실어증으로 구분하지 않는다. 실어증은 언어적 손상을 나타내지만, 모든 언어에서 같은 특성을 나타내지는 않는다. 실어증 환자의 언어적 양상을 평가할 수 있는 방법으로는 자발화 분석이 많이 사용되고 있다. 자발화 분석은 실어증 환자의 다양한 언어적 능력을 반영해주는 좋은 지표이다. 따라서 본 연구에서는 한국어 및 영어를 사용하는 실어증 환자들의 과제의 종류에 따라 나타나는 언어학적 손상의 특징을 비교하고자 하였다. 본 연구에서는 좌뇌반구 뇌졸중으로 인한 실어증 환자들 중 실어증 유형과 중증도를 고려하여 한국어 사용 실어증 환자 14명과 영어 사용 실어증 환자 15명을 대상으로 대화하기 과제와 연속그림설명하기 과제를 통해 한국어와 영어 간 실어증 환자의 언어학적 특성을 살펴보았다. 본 연구의 결과는 다음과 같다. 첫째, 총 발화 수, 동사의 유형 수, 한 발화 당 명사와 동사의 수, 총 개수와 유형의 동사 대 명사 비율(VNR)에서 한국어 사용 실어증 환자가 영어 사용 실어증 환자에 비해 유의하게 높은 수와 비율이 나타났다. 하지만, 영어 사용 실어증 환자가 한국어 사용 실어증 환자에 비해 더 많은 발화를 산출하는 경향이 나타났다. 둘째, 과제에 따라 총 발화 수, 명사의 수와 유형, 동사의 수와 유형, 한 발화 당 동사의 수, 유형에 따른 동사 대 명사 비율(VNR)이 유의하게 나타났다. 또한, 수에 따른 동사 대 명사 비율(VNR)도 미미하지만 유의하게 나타났다. 전반적으로 한국어 및 영어 사용 실어증 환자들이 연속그림 설명하기 과제에 비해 대화하기 과제에서 더 많은 발화, 명사, 동사를 산출하는 것으로 나타났다. 셋째, 한 발화 당 명사와 동사의 수에서 과제에 따른 그룹 간 이차상호작용이 유의한 것으로 나타났다. 한 발화 당 명사의 수는 한국어 사용 실어증 환자는 대화하기 과제에 비해 연속그림 설명하기에서 높게 나타났으며, 영어권 실어증 환자는 반대로 대화하기 과제에서 더 많은 명사의 사용을 보였다. 또한, 한국어 사용 실어증 환자는 연속그림설명하기 과제에서 더 많은 동사의 수를 사용하였으나, 영어 사용 실어증 환자는 대화하기와 연속그림 설명하기 과제에서 차이를 거의 보이지 않았다. 결론적으로, 본 연구에서는 ‘대화하기’ 와 ‘연속그림설명하기’ 자발화 과제에서 한국어 사용 실어증 환자들이 영어 사용 실어증 환자들에 비해 다양한 동사를 산출한다는 점을 시사하였다. 이는 한국어 사용 실어증 환자들이 영어 사용 실어증 환자들에 비해 동사의 표현에 대한 손상이 적다는 것을 나타낸다. 한국어는 동사가 문장 구성의 핵심적인 요소이다. 언어적 손상이 있는 한국어 사용 환자들은 문장 구성의 핵심요소는 보다 적게 손상된다는 것을 시사한다. 또한, 다양한 자발화 과제의 사용이 실어증의 발화특성을 평가하고 중재에 도움이 된다는 점을 시사하였다. 이는 대화하기 과제가 실어증 환자의 일상생활을 반영하여 그림설명하기 과제보다 높은 수행력을 보인다는 선행연구와도 일치하였다. 후속연구로는 두 언어 간 실어증 환자의 유형별 언어적 특성을 비교해보는 연구가 진행되길 기대해본다.;Aphasia is an acquired language disorder that emerges across modalities including receptive and expressive domains. It is caused by brain damage and can coexist with other neurogenic disorders such as motor speech disorders, although cognitive disorders are excluded when diagnosing aphasia (McNeil & Pratt, 2001). Linguistic symptoms may differ by language, and aphasic symptoms are likely to be affected by unique linguistic features of the language that individuals with aphasia used premorbidly. Considering that the language-specific features could influence individual symptoms of aphasia, it is important to investigate the language-specific differences among aphasic symptoms as well as how these differences affect syndromes of aphasia. The competition model accounts for aphasic symptoms based on the unique linguistic characteristics of the language that aphasic individuals used premorbidly rather than syndrome-based differences across the types of aphasia. According to the competition model, instances of the same type of aphasia may demonstrate different linguistic features across languages (Bates & Wulfeck, 1989). The current study performed crosslinguistic comparisons in Korean and English, given that these two languages have contrasting syntactic structures. Korean is a verb-final language, following the word order of Subject–Object–Verb (SOV). As long as the predicate is retained at the end, other linguistic constituents can be scrambled freely within a sentence (Sohn, 2001). In contrast, English follows a word order of Subject–Verb–Object (SVO), and word order information is a critical factor in interpreting thematic relations of a sentence in English (Bates, Friederici, & Juarez, 1988). On the other hand, grammatical morphology, such as case markers, plays a critical role in denoting thematic roles in languages with a relatively free word order such as Korean. The purpose of the current study is to examine crosslinguistic differences in personal narratives and picture description tasks between Korean- and English-speaking individuals with aphasia. Spontaneous speech is one of the most commonly used elicitation measures in evaluating syndromes and severity of aphasia because it demonstrates a wide range of communication abilities. Many studies have examined spontaneous speech in aphasia patients to examine symptoms. However, few studies have conducted crosslinguistic studies in aphasia using elicited tasks. Crosslinguistic studies in aphasia could give an implication of language-specific effects across language, given that aphasic individuals’ premorbidly used language breakdown would provide a basis for applying the competition model. The measures most frequently used to elicit spontaneous speech include narrative tasks and picture description tasks. These two different ways of eliciting spontaneous speech may tap into different cognitive and linguistic domains. Researchers have reported that a picture description task may place greater demands on the individual than narrative tasks do, as the picture description paradigm is presented in a more constrained way (Deloche, Jean-Louis, & Seron, 1979). Twenty-nine individuals with aphasia with a single, left-hemisphere stroke participated in this study. Participants consisted of fourteen Korean-speaking individuals with aphasia and fifteen English-speaking individuals with aphasia. Data for the English group are taken from the “Aphasia Bank Project” (MacWhinney, Fromm, & Holland, 2011). Personal narratives and sequential picture description tasks were used in the present study. The experimental materials were obtained from the Aphasia Bank Protocol. For the Korean participants, the English protocols were translated into Korean. In personal narratives tasks, participants were asked about the current status of their speech, how they suffered stroke, and their recovery from stroke. Troubleshooting questions were asked to encourage them when participants struggled. For the sequential picture description task, six cuts of the sequential story of a boy refused an umbrella were used. Linguistic outcome measures included total number of utterances, total number and different numbers of nouns and verbs, number of nouns per utterance, number of verbs per utterance, tokens for verb-to-noun ratio (VNR), and types for VNR. Two-way mixed ANOVAs were conducted to analyze differences between the Korean- and English-speaking groups depending on the type of elicitation tasks (personal narratives and sequential picture description tasks). The results revealed, first, that the Korean speaking individuals with aphasia rated higher in different number of verbs, number of nouns per utterance, number of verbs per utterance, tokens for VNR, and types for VNR. However, the English-speaking group had higher total numbers of utterances in both personal narratives and sequential picture description tasks. Second, there were significant task-type differences in total number of utterances, total number and different numbers of nouns and verbs, number of verbs per utterance, and tokens and types for VNR. Both Korean- and English-speaking individuals with aphasia generated more linguistic units in utterances, nouns, and verbs in personal narratives than in the sequential picture description task. Third, the two-way interactions were significant in number of nouns per utterance and number of verbs per utterance. The interactions in number of nouns per utterance are due to the fact that the Korean-speaking group produced more nouns in the sequential picture descriptions than in the personal narrative tasks, while the opposite was observed for the English-speaking group. In terms of the interaction for the number of verbs per utterance, the Korean group generated more numbers of verbs in the sequential picture description tasks than the personal narrative tasks compared to the English group. The interactions in number of verbs per utterance occurred because the Korean-speaking group produced more verbs in the sequential picture descriptions than in the personal narrative tasks, while the English-speaking group performed similarly in both personal narratives and the sequential picture description tasks. The current study found that Korean individuals with aphasia produced more numbers and a greater variety of verbs than the English individuals with aphasia did. The results are consistent with the prediction that Korean speakers with aphasia are less vulnerable to producing verbs than English speakers are, given that Korean is a verb-salient language. In addition, many samples in a wide range of communication situations could be acquired by evaluating different types of spontaneous speech. Personal narratives tasks and sequential picture description tasks were used in this study to analyze an aphasic individual’s spontaneous language. This study revealed that the participants produced more utterances, nouns, and verbs in the personal narrative task than the sequential picture description task. The results are consistent with the prediction that personal narrative tasks are easier for aphasic individuals than describing a sequential picture. This is because the picture description tasks need more combined cognitive process than personal narrative tasks do. Further research in elicited spontaneous speech across types of aphasia could be useful.