Disentangling semantic interference: A Picture-Word Stroop Study in the Aphasic population

One of the most common symptoms of aphasia is impaired word retrieval during spoken word production. Because such deficits can help reveal the mechanisms underlying lexical access, comparisons between people with aphasia (PWA) and healthy controls (HC) in naming tasks can provide important insights into the lexical system. Psycholinguistic research has shown that lexical retrieval is shaped by both semantic context and attentional or control-related mechanisms. In particular, the Picture–Word Interference (PWI) paradigm has been widely used to investigate the Semantic Interference Effect (SIE), whereas the Colour–Word Stroop task has been used to study interference control. Only a limited number of studies, however, have examined these effects in aphasia. The present study investigated lexical access in PWA and HC using a hybrid Picture–Word Stroop task designed to measure both a Stroop-like interference effect and a Semantic Interference Effect (SIE) within the same paradigm. The Stroop-like effect was operationalised as the difference between Congruent and Incongruent trials. Additionally, incongruent trials varied in semantic similarity between target and distractor, allowing assessment of whether graded semantic relatedness modulated naming performance. In addition, because lexical retrieval is influenced by multiple linguistic and non-linguistic factors, the analyses controlled for relevant covariates in a principled, stepwise manner. We evaluated a group of PWA (n = 18) with focal lesions due to stroke or tumour and a matched HC group (n = 32). Naming latencies were examined using analyses ranging from condition-level comparisons to trial-level mixed-effects models. In addition, the analysis was supplemented by analyses of accuracy and qualitative error. Results showed a robust Stroop-like interference effect in both groups, which was significantly larger in PWA than in HC. This pattern converged across condition-level analyses, conflict-ratio measures, accuracy data, and qualitative error analyses. By contrast, the semantic interference effect was weaker and less consistent, with the evidence varying across levels of analytic specificity. These findings suggest that PWA are especially vulnerable to broad distractor-related conflict during naming, whereas effects of graded semantic similarity are subtler and more sensitive to methodological choices. More broadly, the study highlights both the feasibility of the Picture–Word Stroop task in aphasia research and the importance of methodological rigour when interpreting interference effects in lexical access.