## 2 Materials and Methods
### Stimuli, Experimental Procedure, and Task  
The experiment was carried out on a PC running on a Windows operating system, which was located in a computer room. An open-source Experiment generator software (Working Memory Analyser, version 1.0.2.2) programmed in Lazarus free Pascal ([[https://www.lazarus-ide.org](https://www.lazarus-ide.org)]([https://www.lazarus-ide.org](https://www.lazarus-ide.org))) using OpenGL and Simple Direct media Layer (SDL2) libraries was used to run the visual paradigm. To promote the replicability of this study across laboratories, the software, including the experimental library of the experiment used in this study, was distributed under the GPL-3.0 license, and it can be downloaded from its GitHub repository ([[https://github.com/gfuggetta-lab/WorkingMemoryAnalyser/releases](https://github.com/gfuggetta-lab/WorkingMemoryAnalyser/releases)]([https://github.com/gfuggetta-lab/WorkingMemoryAnalyser/releases](https://github.com/gfuggetta-lab/WorkingMemoryAnalyser/releases)) (accessed on 1 October 2024). Stimuli were presented on a 24\({}^{\prime\prime}\) (53.1 cm \(\times\) 29.9 cm) AOC G2460 PG LCD monitor with a resolution of 1920 \(\times\) 1080 pixels and a refresh rate of 59.940 Hz at a viewing distance of 88 cm. To ensure accurate synchronization with millisecond precision between the onset of the visual stimuli on screen and the markers on the EEG recording system, the Trigger Station device (BrainTrends Ltd., Rome, Italy, [[https://www.braintrends.it/](https://www.braintrends.it/)]([https://www.braintrends.it/](https://www.braintrends.it/))) was used. For the modified and delayed match-to-sample task, the monitor continuously displayed a 0.1\({}^{\circ}\) white fixation dot (21.5 cd/m\({}^{2}\)) at the center of an 11.84\({}^{\circ}\) grey circle (6.5 cd/m\({}^{2}\)), shown against a black background (see Figure 1). Four empty white rings (i.e., placeholders, 21.5 cd/m\({}^{2}\)) with an outer diameter of 1.30\({}^{\circ}\) and inner diameter of 1.17\({}^{\circ}\) (0.065\({}^{\circ}\) thickness) were constantly shown in the top-left, top-right, bottom-left, and bottom-right quadrants on the circumference of an imaginary circle of 9.20\({}^{\circ}\) diameter around the central fixation dot. The visual paradigm comprised the following stimuli in sequential order: First, a foveally presented fixation, which was a 0.78\({}^{\circ}\)\(\times\) 0.78\({}^{\circ}\) grey (21.5 cd/m\({}^{2}\)) cross, appeared at the beginning of each trial for 500 ms. Second, after an interval of 500 ms, a sample array (i.e., memory set of items) comprising four objects presented in the top-left, top-right, bottom-left, and bottom-right quadrants on the circumference of an imaginary circle of 2.66\({}^{\circ}\) diameter around the central fixation dot was shown for 2000 ms. These four objects could either be three grey circles and one grey abstract shape (i.e., low VWM capacity load of 1) or four grey abstract shapes (i.e., high VWM capacity load of 4). All objects had a size of 0.84\({}^{\circ}\). In terms of non-nameable abstract shapes, sixteen stimuli (  
Figure 1: Example of the stimuli of a trial of the modified, delayed match-to-sample task. Each trial began with the presentation of a fixation cross, followed by a sample array (i.e., memory set). A distractor array was interleaved during the retention interval, showing a task-irrelevant ”singleton” item. The singleton was a Chinese character that was not part of the current task set. The trial ended with a memory probe (i.e., target) followed by a response time interval and visual feedback. Participants were asked to hold the memory set in mind during the retention interval and decide whether the memory probe was matching or mismatching any of the items presented as part of the sample array (i.e., match-to-sample task). They were also instructed to ignore the distractor array and fixate on the central fixation dot throughout the experiment.