When Students Control Information Onset: Disentangling Effects of Motor Self-Initiation and Temporal Predictability on Working Memory

Learner-paced digital environments require students to self-initiate the onset of instructional content, yet the cognitive mechanisms by which this control affects information encoding remain poorly understood. The present study examined whether motor self-initiation and temporal predictability contribute independently or interactively to working memory (WM) performance in secondary school students. Using a 2 × 2 × 2 factorial design, 66 adolescents (M age = 15.18 years) completed a digital Backward Digit Span task across four conditions crossing motor control (self-initiation vs. automatic-initiation, within-subjects) and temporal predictability (high temporal prediction vs. low temporal prediction of stimulus onset timing, within-subjects), in either visual (n = 32) or auditory (n = 34) stimulus modality. Mixed-effects logistic regressions revealed a significant main effect of motor control, with self-initiated trials yielding higher WM accuracy than automatic trials. This effect was qualified by a significant interaction between motor control and temporal predictability: accuracy was lower specifically when stimulus onset was both externally initiated and temporally predictable, and comparable across the remaining three conditions. No effects of perceptual modality were detected. These findings suggest that motor self-initiation and temporal predictability act as partially substitutable sources of encoding preparation in adolescent learners, as WM accuracy declined only when neither self-initiation nor temporal uncertainty was available, carrying implications for the design of learner-paced instructional environments.