## 3 Methods
### Materials and Procedures
#### 3.2.2 The Web-Based Assessment Platform \"STM Suite\"
For conditions with visual presentation, lists of the same length belonging to a pair had identical characteristics except for the presence/absence of AS, and they were administered in the same block in an alternating pattern. Thus, the first list was the 3-item one without AS, followed by the 3-item one with AS, followed by the 4-item one without AS, followed by the 4-item one with AS, and so on, with the last possible list being the 7-item one with AS. Since no AS could be applied in auditory input conditions, the alternation schema was preserved through the use of parallel (no-AS) lists of identical lengths. Hence, in the case of auditory presentation, the initial 3-item list was followed by another different 3-item list, then by a 4-item list, then by a different 4-item list, and so on (all without AS). Before the start of the first list of a new block, a training trial was administered to facilitate task comprehension. Letters were presented visually, printed in capital, Lucida Handwriting fonts, while their auditory/oral counterpart was their own exact spelling. Colour stimuli included 15 nuances, chosen from those considered most familiar and recognizable by children (pink, #FFC0 CB; blue, #0000 FF; black, #000000; violet, #EE82 EE; green, #008000; dark grey, #A9A9A9; orange-red, #FF4500; Yellow, #FFFF0, saddle brown, #8B4513; beige, #SF5F5 DC; fuchsia, #FF00 FF; powder blue, #B0E0E6; gold #FFD700; white, #FFFF; red, #FF0000). The  
Figure 1: “STM Suite”: trial and item structures. whole set of stimuli along with their names (used in the auditory presentation condition) is provided in the Supplementary Materials (Figure S1). All stimuli could be presented in either the visual or the auditory/verbal modality. Stimuli presented in the visual modality could appear either in sequential presentation (one after the other, with a 500 ms interval) or in simultaneous presentation mode (altogether, with an exposure time equal to 1000 ms for each presented item). The presentation sequence was as follows: (a) appearance of a point of fixation; (b) appearance of the stimuli to be memorized in the upper half of the screen (in sequential or simultaneous modality); (c) disappearance of the previously presented stimuli; and (d) the subsequent reappearance of the same items, but in a different order, with or without distractors. In the visual stimulus presentation modality, stimuli (coloured rectangles or letters) appeared on the screen, either at the centre of the screen (sequential modality: each stimulus lasted for 0.5 s, with ISI = 0.5 s) or in a horizontal row (simultaneous modality: the full list was displayed for N s, with N = list length). In the auditory stimulus presentation modality, stimuli were colour names or letter names previously recorded with an Italian mother-tongue female voice lacking any inflexion or specific intonation, presented sequentially via headphones (ISI = 0.5 s). The response could be either oral or visual-motor. In the \"oral response\" modality, participants simply had to repeat the list of items they had just been presented with, in the correct order. By contrast, in the \"visual-motor\" response modality, after having been administered a stimulus list, the subjects were shown a set of (random order) candidate items on the screen and had to reconstruct the original list by dragging them with the mouse pointer, dropping them (one by one) in a horizontal row within an empty, standard dark grey rectangle (the response list space), and, finally, clicking \"end\" to indicate that response was complete and they were satisfied with the provided sequence (Figure 2). When the lists contained distractors, the items that were initially presented reappeared on the screen for the response, mixed with other items. There were four distractors for each list (Figure 3). The presence of distractors during recognition/reconstruction (visual-motor response) was introduced so as to allow for the simultaneous assessment of item and order STM.