Investigating comprehension of nouns and verbs: is there a difference?

ABSTRACT

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.

Methods & Procedures: 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.

Outcomes & 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.

KEYWORDS:

• Lexical-semantic comprehension
• standardized assessment
• verb comprehension
• noun comprehension

Acknowledgements

We extend gratitude to Prof. Viktor Markovich Shklovsky and the staff of the Center for Speech Pathology and Neurorehabilitation, in particular Ekaterina Iskra, Svetlana Kuptsova, and Elena Kozintseva, for assistance with participant recruitment and data collection. We thank Dmitry Isaev and Yulia Akinina for their help in the development of the experimental tasks and the presentation program. We are also immensely grateful to the members of the Neurolinguistics Laboratory of National Research University Higher School of Economics for their comments on an earlier version of the manuscript.

Disclosure statement

The authors report no conflicts of interest.

Notes

1. This test contains subtests for production and comprehension of oral and written speech and its total score is used to determine the severity of the aphasia (for detailed description, see Ivanova, Dragoy, Kuptsova, Ulicheva, & Laurinavichyute, 2015).

2. Measure of uniformity of names used by different participants to refer to a depicted object or action.

3. The degree to which a visually depicted object or action corresponds to the mental image generated in response to the presentation of a word.

4. The degree of the complexity of the picture regarding the number of details and lines.

5. The duration of the recorded noun stimuli was on the average slightly shorter than that of the verb stimuli (M_{verb − noun} = 105.1 ms). However, all the observed significant effects remained unchanged after correcting for this difference in the duration of audio stimuli in the analyses. Since this duration difference does not account for the observed effects, below we report the results without this correction.

6. As mentioned earlier, our groups of PWA and NBD differed significantly in the level of their formal education (t = 2.57, p = .014). However, correlation analysis did not reveal significant impact of the number of years of formal education on accuracy [PWA: nouns: r(32) = −.03, p = .863; verbs: r(32) = −.14, p = .426; NBD: nouns: r(20) = −.25, p = .292; verbs: r(20) = −.9, p = .702] or on RTs [PWA: nouns: r(32) = .01, p = .961; verbs: r(32) = .01, p = .942; NBD: nouns: r(20) = .03, p = .889; verbs: r(20) = .14, p = .565] in both subtests. Thus, level of education was not an influential factor and we did not use it as a covariate in our analyses.

Additional information

Funding

The article was prepared within the framework of the Basic Research Program at the National Research University Higher School of Economics (HSE) and supported within the framework of a subsidy by the Russian Academic Excellence Project “5-100”.