The Role of Working Memory Load in Distractor Suppression

  • Rebecca Saw

Student thesis: Doctoral Thesis


The well-established Load Theory of Attention and Cognitive Control (Load Theory) has sparked research over two decades. There are two integral components of Load Theory, i.e. ‘cognitive load’ and ‘perceptual load’ with the former concept receiving less attention in the literature. The core assumptions of Load Theory, with an emphasis on ‘cognitive load’,have been systematically investigated in this thesis using electroencephalography (EEG) and transcranial magnetic stimulation(TMS). The current research uncovered robust working memory (WM) effects in the healthy youngeradult populationwhich partially supported Load Theory. Experiment 1 revealed that the WM load effect on distractor processing increases when more items were held in WM but can plateau at a certain set-size(i.e.,3 items). In Experiment 2, the direction of distractor interference was inconsistent across the behavioural measures of reaction times and error rates, with the latter in support of Load Theory. In contrast, therewas strong electrophysiological evidence (i.e.,the N2pc and Pd components) for increased susceptibility to peripheral distractors under low WM load conditions (remembering one item). The behavioural effects of Experiments1and 2 which partially supported Load Theory, were not replicated with a TMS protocol (Experiment 3). There were significant effects, partially supporting Load Theory, when the spatial position of distractor and a subsequent target item was considered. Altogether, the findings have contributed to a clearer understanding of WM load effects, especially in terms of the attentional processes involved in distractor processing within a single-task setting. The results have provided recommendations of factors which were omitted in Load Theory such as the distinction of functions (updating and shifting) rather than positing a general executive load. This understanding can inform future research specifically targeting visual processing, WM and selective attention processes which can be extrapolated to everyday situations where attention to detail is crucial.
Date of Award17 May 2022
Original languageEnglish
Awarding Institution
  • University of Roehampton
SponsorsUniversity of Roehampton Vice-Chancellor’s Scholarship
SupervisorGiorgio Fuggetta (Director of Studies), Amanda Holmes (Co-Supervisor) & Marco Sandrini (Co-Supervisor)


  • Working Memory
  • Visual Selective Attention
  • Load Theory
  • Electroencephalography
  • Transcranial Magnetic Stimulation

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