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Article

Investigating Comprehension of Nouns and Verbs: Is There a Difference?

Aphasiology. 2018. Vol. 2. No. 32. P. 183-203.

Background: There is growing evidence that verbs are often more difficult to process than nouns and that verb retrieval is more commonly affected in aphasia. However, existing observations are largely based on naming and semantic judgment tasks. The extent to which this processing difficulty is modality-general has yet to be established. In addition, most of the present language batteries do not allow direct comparison between noun and verb comprehension deficits. To fill this gap, a test was developed for the assessment of noun and verb lexical-semantic comprehension.

Aims: The current study investigates whether verb processing difficulties are modality-general by administering novel balanced noun and verb comprehension tasks to participants with and without aphasia.

Method: In this study we directly compare the difficulty of comprehension of verbs versus nouns in a group of participants with aphasia (PWA, n = 32) and non-brain-damaged, age-matched participants (NBD, n = 20). The word comprehension task was implemented on a tablet measuring accuracy and reaction times (RTs). Participants were required to listen to an aurally presented word and match it to one of four pictures (a target and three distractors: semantic, phonological and irrelevant) by tapping on it with the non-dominant hand. In total, 30 nouns and 30 verbs were presented.  The verbal stimuli in the two tasks were matched on relevant psychometric properties such as familiarity, age of acquisition, subjective visual complexity, imageability, image agreement and frequency.

Results: Both groups experienced more difficulties in the verb comprehension task, indicated by lower accuracy and longer RTs in PWA and longer RTs in NBD. PWA who were performing the task within normal limits (i.e., demonstrated no difference in accuracy compared to the control group) still showed significantly longer RTs in the verb task than controls.  Also, PWA who demonstrated similar accuracy in both tasks had longer RTs in the verb task relative to the noun task. The pattern was general and no differences were observed in performance between participants with fluent and non-fluent aphasia types. Moreover, the observed dissociations in RTs were greater for PWA than for NBD, indicating that a damaged language system experiences even more difficulties in processing verbs.  

Conclusions: Overall, the study demonstrated the relative difficulty of verb processing in a comprehension task, supporting the hypothesis that verb processing difficulties are modality-general. The new test allows researchers to compare performance on noun and verb comprehension and registers even subtle differences by measuring RTs. Background: There is growing evidence that verbs are often more difficult to process than nouns and that verb retrieval is more commonly affected in aphasia. However, existing observations are largely based on naming and semantic judgment tasks. The extent to which this processing difficulty is modality-general has yet to be established. In addition, most of the present language batteries do not allow direct comparison between noun and verb comprehension deficits. To fill this gap, a test was developed for the assessment of noun and verb lexical-semantic comprehension.

Aims: The current study investigates whether verb processing difficulties are modality-general by administering novel balanced noun and verb comprehension tasks to participants with and without aphasia.

Method: In this study we directly compare the difficulty of comprehension of verbs versus nouns in a group of participants with aphasia (PWA, n = 32) and non-brain-damaged, age-matched participants (NBD, n = 20). The word comprehension task was implemented on a tablet measuring accuracy and reaction times (RTs). Participants were required to listen to an aurally presented word and match it to one of four pictures (a target and three distractors: semantic, phonological and irrelevant) by tapping on it with the non-dominant hand. In total, 30 nouns and 30 verbs were presented.  The verbal stimuli in the two tasks were matched on relevant psychometric properties such as familiarity, age of acquisition, subjective visual complexity, imageability, image agreement and frequency.

Results: Both groups experienced more difficulties in the verb comprehension task, indicated by lower accuracy and longer RTs in PWA and longer RTs in NBD. PWA who were performing the task within normal limits (i.e., demonstrated no difference in accuracy compared to the control group) still showed significantly longer RTs in the verb task than controls.  Also, PWA who demonstrated similar accuracy in both tasks had longer RTs in the verb task relative to the noun task. The pattern was general and no differences were observed in performance between participants with fluent and non-fluent aphasia types. Moreover, the observed dissociations in RTs were greater for PWA than for NBD, indicating that a damaged language system experiences even more difficulties in processing verbs.  

Conclusions: Overall, the study demonstrated the relative difficulty of verb processing in a comprehension task, supporting the hypothesis that verb processing difficulties are modality-general. The new test allows researchers to compare performance on noun and verb comprehension and registers even subtle differences by measuring RTs.