Increase of phonological errors in dual-task conditions in patients with aphasia and neurotypical individuals: Impact of the verbal nature of the concurrent task

Speaking is affected under dual-task conditions and studies have shown an impact on lexical and on phonological processes even in single word production. In the present study, we aimed at investigating if dual-task interference on lexical and phonological encoding is modulated by the linguistic nature of the concurrent task and in particular to determine whether the increase of phonological errors observed in previous studies using auditory syllables as concurrent stimuli is due to the phonological overlap between the tasks. Patients with aphasia (PWA, Experiment 1) and neurotypical individuals (Experiment 2) underwent a picture naming task and an auditory detection task of non-verbal sounds of daily life under single and dual-task conditions with different stimulus onset asynchronies (SOAs), namely +150 and + 300 ms, likely targeting lexical processes and phonological encoding. In both groups, naming latencies were slower under dual-task conditions at each SOA and in PWA, phonological errors increased with sounds of daily life presented at SOA +300. The results on errors replicate what was observed previously in studies using syllables as concurrent auditory stimuli in PWA. To investigate whether the increase of errors is larger with syllables relative to non-verbal sounds independent of the clinical condition, another neurotypical group performed a dual-task paradigm with syllables as concurrent auditory stimuli (Experiment 3). RESULTS: showed an increase of phonological errors at late SOA also in neurotypical participants, thus confirming the impact of concurrent syllables on phonological errors independently of the population. The results indicate that non-verbal auditory stimuli in the concurrent task impact phonological errors, although to a lesser extent than syllables, suggesting that the increase of errors in previous studies cannot be entirely attributed to the phonological overlap between the tasks.