People frequently perform multiple tasks at a time in daily life, and speech is commonly involved. Although many dual tasks can be managed without difficulty, evidence indicates that when speech and fine motor actions compete for shared neural resources, interference can occur. Understanding when such costs emerge is particularly relevant for ageing, lateralisation, and clinical contexts. This thesis investigated how speech–motor dual tasking is shaped by age, hand preference, and task complexity, while also examining the feasibility of administering such paradigms online.
The study was guided by three hypotheses: that dual task performance would be reduced relative to single-task performance, that more complex combinations would produce greater decrements, and that the preferred hand would confer an advantage over the nonpreferred hand. A further aim was to validate online testing as a scalable approach for dual task research.
Twenty-seven participants (18 younger, 9 older adults) completed baseline and dual task conditions pairing speech tasks of varying linguistic load with manual tasks of increasing complexity. Performance was analysed using dual task costs, ANOVAs, t-tests, and non-parametric tests where appropriate.
The findings indicated that task complexity was the strongest determinant of dual task costs. High-load pairings such as complex tapping or coin rotation with speech produced interference, whereas one low-load pairing (Simple Finger Tapping with Single Word Repetition) yielded facilitation. No statistically significant effects of age or hand preference were observed, although descriptive patterns suggested age-related trends.
In conclusion, the thesis advances understanding of speech–motor dual tasking by identifying task complexity, rather than age or hand use, as the behavioural driver of performance, and by demonstrating feasibility of online testing for dual task paradigms. Findings are interpreted within established frameworks, suggesting interference and facilitation reflect task-dependent coordination demands rather than direct neural evidence, and provide a foundation for future research.
