Larissa Leist

• The Irrelevant Sound Effect (ISE) describes the phenomenon that serial recall of visually presented verbal items, such as digits, letters, or nouns, is impaired by the presence of specific task-irrelevant background sounds. This effect highlights the auditory system’s inherent tendency to automatically process environmental stimuli, regardless of their relevance to the current task. Understanding the ISE is crucial for both theoretical and practical reasons, as most adults and children work or study in noisy environments. Theoretical explanations of the ISE vary. Some theories suggest that background sounds divert attention away from the to-be-remembered items, while others propose that the effect arises from competing seriation processes between the background sounds and the serial order of the memory material. Additionally, the ISE might impact the short-term memory system by disrupting the phonological representations of verbal items in the phonological store. Research on the ISE has revealed inconsistent findings between children and adults, indicating that the effect may differ across age groups. It is often argued that children might be more vulnerable to task-irrelevant background sounds due to their less developed attention mechanisms. Moreover, while behavioral studies consistently demonstrate the detrimental impact of the ISE on performance, the neurophysiological mechanisms underlying this effect remain less well understood. Investigating event-related potential (ERP) components such as the N1, P3a, and MMN can provide valuable insights into various stages of auditory cognitive processing, from early processing demands, to the brain’s pre-attentive auditory discimination mechanisms and automatic orienting responses. Exploring both age-related variations and the neurophysiological mechanisms of the ISE could offer deeper insights into how auditory stimuli influence attention and cognitive performance. The overall purpose of this thesis is to disentangle the roles of seriation, phonological processing and attention capture in the ISE, based on how this effect is evoked. It outlines various theoretical explanations for the ISE, highlights inconsistencies in its impact across different age groups, and underscores the importance of investigating both behavioral and neurophysiological aspects to gain deeper insights into how auditory distractions affect serial order retention. In the present thesis, behavioral experiments (Studies 1–4) combined with EEG methodology (Studies 5–6) were performed to investigate the roles of seriation, phonological processing and attention in the ISE.