Fig 2. Learning scores of the two groups during the learning and the retrieval phase.

The vertical axis represents the learning scores (the difference between RTs for high- and low-probability triplets) in ms, and the horizontal axis represents the nine units of five blocks of the learning phase (block 1–45) and the four units of five blocks of the retrieval phase (blocks 1–5, blocks 6–10, blocks 12–16, blocks 18–22). The black line represents the learning scores of the dual-task group, and the grey line the learning scores of the single-task group. The squared block units represent the test blocks, i.e., when the secondary task was also performed by the dual-task group. The error bars represent the standard error of the mean. At the beginning of the retrieval phase, stable statistical knowledge was detected in blocks 1–5. The statistical knowledge remained stable in the later parts of the retrieval phase, even during the test blocks, and no difference was found between groups in terms of learning scores. We found similar results with standardized scores.