A Comparative Study on Statistical Learning Abilities in Persons with Aphasia and Neuro-Typical Individuals

Abstract

Learning system involves implicit and explicit forms that are distinctive in learning, processing, storing, and retrieving knowledge. These learning systems are involved in a variety of aspects of learning throughout life. If one of the learning systems is defective, the other can be utilized to compensate or complement it. Several studies have demonstrated that the implicit system is considerably more robust to neurological diseases than the explicit system. The knowledge gained from implicit learning can be retained for longer periods. In light of these considerations, implicit-based statistical learning was studied to determine the learning potential of Persons with Aphasia (PWA) who had a recent episode of brain injury resulting in the loss of skills and routines. In an attempt to improve the methodological aspects from previous research, characteristics such as response mode, task version, stimulus characteristics of the Serial Reaction Time Task (SRTT), and time course of learning consolidation and retention of knowledge were incorporated in the experimental design. In addition, the current study was carried out within a theoretical and clinical framework connecting the measures designed to assess non-linguistic task performance with methods aimed at tapping statistical learning and correlating performance with linguistic competence and cognitive capabilities. The substantial research on these lines has been investigated in the Western context, emphasizing the significance of the present study. In the Indian context, only a few studies in the clinical population, i.e., individuals with specific language impairment and dyslexia, have been reported. As cultural differences exist between westerners and Southwest Asians, resulting in differences in cognitive processing abilities, it is vital to study in an Indian setting to validate earlier findings. Thus, the present study aimed to investigate statistical learning abilities in PWA and Neuro-Typical Individuals (NTI). 2 The experiment included 15 PWA and 15 NTI participants in the study. To examine statistical learning, cognitive abilities, and language comprehension, the researcher utilized the SRTT, modified-SRTT, n-back, four-choice reaction time task as attention task and sentence judgment task, respectively. In addition, the consolidation of learning from SRTT was measured after one day and three days from the initial session/day of testing. The performance across all tasks and the relationship between measures were analyzed using appropriate descriptive and inferential statistics. Following statistical analysis, one PWA data set was found to be an outlier. As a result, the performance data of 14 PWA and 15 NTI were only used for further analyses. The results of the study revealed a significant difference between PWA and NTI groups in SRTT. Nevertheless, no significant difference was observed between subtypes of aphasia. The performance on explicit recall of SRTT measured on the third session showed a substantial difference between PWA and NTI. In comparison to PWA, NTI had better consolidation. Besides this, on the modified-SRTT measure, there was no significant difference between PWA, NTI, and aphasia subtypes. Further, the results indicated a substantial difference in performance between the two groups on the working memory task, but contrasted findings on the attentional task were noted. According to statistical analysis, no correlation between statistical learning and working memory and attentional task performance was found. In sentence judgment task, a significant difference in accuracy and reaction time measurements between PWA and NTI across sentence kinds and overall, according to results. However, there was no significant difference between Persons with Non-Fluent Aphasia (PWNFA) and Persons with Fluent Aphasia (PWFA) on any of the sentence judgment task measures. In addition, correlation results revealed a significant correlation between the specific measure of SRTT with performance on sentence judgment task. The implications, limitations, and future directions of the study are discussed in detail.