Coin task
Performance
For performance time, results revealed a significant main effect of time, F (3.08, 67.712) = 48.19, p < .001, ηp2 = .687, a significant main effect of group, F (1, 22) = 6.94, p = .015, ηp2 = .712, but no time x group interaction, F (5, 110) = 0.772, p = .572, ηp2 = .034. Pairwise comparisons showed that the MT group performed significantly faster at T3 compared to B1 (p < .001) and T1 (p = .020), after which no further improvements were made (p = 1.00). Similar results were found for the GT group, who performed faster at T3 compared to B1 (p < .001), T1 (p = .001), and T2 (p = .091), but subsequently plateaued at retention and delayed retention (p = 1.00). Importantly, comparisons also revealed that whilst there were no significant difference between groups at B1 (p = .638) and T1 (p = .108), the GT group performed significantly faster than the MT group on all subsequent visits (ps = .022).
For performance error, results failed to reveal a significant main effect of time, F (5, 110) = 2.101, p = .071, ηp2 = .087, suggesting the number of coin drops to be fairly insensitive to practice. There was also no main effect of group, F (1, 22) = 0.481, p = .495, ηp2 = .021, and no time x group interaction, F (5, 110) = 0.745, p = .592, ηp2 = .033.
Target locking score (TLS)
Results revealed a significant main effect of time, F (1.56, 34.24) = 9.97, p < .001, ηp2 = .312, a main effect of group, F (1, 22) = 35.212, p < .001, ηp2 = .410, and a significant time x group interaction, F (2, 44) = 13.481, p < .001, ηp2 = .380. Post-hoc pairwise comparisons revealed no difference between groups at baseline (p = .686), but the GT group to exhibit significantly higher TLS compared to the MT group at retention and delayed retention (p < .001). Participants in the MT group showed no significant improvement from baseline to retention (p = 1.00) or baseline to delayed retention (p = 1.00). Conversely, the GT group significantly increased their TLS from baseline to retention (p < .001) and delayed retention (p < .001).
Gaze shifting
Results revealed a significant main effect of time, F (1.29, 28.42) = 34.269, p < .001, ηp2 = .609, a main effect of group, F (1, 22) = 26.902, p < .001, ηp2 = .550, and a significant time x group interaction, F (2, 44) = 8.361, p = .001, ηp2 = .279. Post-hoc pairwise comparisons revealed no difference between groups at baseline (p = .586), but the GT group to exhibit significantly faster gaze shifts than the MT group at retention (p = .001) and delayed retention (p < .001). They also revealed both the MT group (ps = .018) and the GT group (p < .001) shifted their gaze significantly faster from baseline to retention and delayed retention. Performance data and gaze data can be seen in Fig. 4.
Alpha power
For the coin task, the ANOVA also showed a significant main effect of ROI, F (3.712, 70.530) = 87.703, p < .001, ηp2 = .822, revealing a focal pattern in which alpha was lowest over central and parietal regions, higher over temporal and frontal regions, and highest over the occipital region. There was also a significant main effect of time, F (2, 40) = 3.279, p = .049, ηp2 = .049, and a significant time x ROI interaction, F (6.685, 127.022) = 2.819, p = .010, ηp2 = .129. Pairwise comparisons revealed that both groups exhibited a significant decrease over the left-temporal (p = .001) and right temporal (p = .042) regions from baseline to delayed retention. All other interactions were non-significant (Fig. 5).
High alpha connectivity
When examining cross hemispheric (T7 vs T8) changes in temporal-frontal (Fz) connectivity, results showed no overall main effect of time, F (2, 40) = 0.427, p = .655, ηp2 = .021, and no overall main effect of group, F (1, 20) = 0.156, p = .697, ηp2 = .008. There was however a significant time x group interaction, F (2, 40) = 3.387, p = .044, ηp2 = .145, and a significant time x hemisphere x group interaction, F (2, 40) = 4.532, p = .017, ηp2 = .185. Pairwise comparisons revealed that participants in the GT group exhibited a significant reduction in T7-Fz connectivity from baseline to delayed retention (p = .043), and a marginally significant reduction from baseline to retention (p = .056). No changes were observed in the MT group (Fig. 5).
Δ high alpha connectivity
Results from ANOVA showed no effect of time, F (1, 20) = 0.260, p = .616, ηp2 = .013, hemisphere, F (1, 20) = 3.333, p = .083, ηp2 = .143, or group, F (1, 20) = 4.284, p = .052, ηp2 = .176. There was however a significant hemisphere x group interaction, F (1, 20) = 7.934, p = .011, ηp2 = .284, in which a significant difference between groups was observed only for the change in T7-Fz connectivity (p = .003). Pairwise comparisons also showed an overall significant difference between hemispheric changes for the GT group (p = .003) which consisted of a decrease in T7-Fz connectivity and an increase in T8-Fz connectivity.
Regression analyses
At baseline, a non-significant regression equation was found when predicting T7-Fz connectivity based on TLS, F (1, 21) = 0.718, p = .406, r2 = .033, and gaze shifting, F (1, 21) = .028, p = .868, r2 = .001. At retention, however, both TLS, F (1, 21) = 4.532, p = .045, r2 = .177, and gaze shifting, F (1, 21) = 8.056, p = .010, r2 = .287, were significant predictors of T7-Fz connectivity. The same was true at delayed retention, with TLS, F (1, 21) = 7.238, p = .014, r2 = .256, and gaze shifting, F (1, 21) = 5.004, p = .036, r2 = .192, again significant predictors of T7-Fz connectivity (Fig. 6).
Transfer tea-making task
Due to time-locking synchronisation errors, EEG data for three participants could not be analysed for the tea-task.
Performance
Results showed no significant difference between the MT (Mdn = 73.20 s) and GT (Mdn = 64.55 s) groups’ performance time at retention (H (1) = 1.763, p = .184). There was also no difference between the MT (Mdn = 57.70) and GT (Mdn = 57.39 s) at delayed retention (H (1) = .033, p = .564).
Target locking score (TLS)
No significant main effect of time F (1, 22) = 3.799, p = .065, ηp2 = .147, but a significant main effect of group, F (1, 22) = 22.328, p < .001, ηp2 = .504, was observed, revealing participants in the GT group to exhibit significantly lower TLS compared to participants in the MT group. There was no significant time x group interaction, F (1, 22) = 0.009, p = .926, ηp2 = 00.
Gaze shifting
Results revealed no main effect of time, F (1, 22) = 2.216, p = .151, ηp2 = .092, no main effect of group, F (1, 22) = 3.151, p = .090, ηp2 = .048, and no time x group interaction, F (1, 22) = 1.115, p = .302, ηp2 = .048.
Alpha power
Results revealed no main effect of time, F (1, 18) = .257, p = .618, ηp2 = .014, or group, F (1, 18) = .195, p = .664, ηp2 = .011, but a main effect of ROI, F (3.495, 62.917) = 27.837, p < .001, ηp2 = .607, revealing alpha power to be lowest over central and parietal regions, and highest overall temporal, frontal and occipital regions. All other interactions were non-significant.
High alpha connectivity
When examining cross hemispheric (T7 vs T8) changes in frontal (Fz) connectivity, results from ANOVA showed no significant main effect of time, F (1, 17) = 3.693, p = .072, ηp2 = .178, or group, F (1, 17) = 3.248, p = .089, ηp2 = .160. There was however a significant main effect of hemisphere, F (1, 17) = 11.694, p = .003, ηp2 = .408, showing overall higher T7-Fz connectivity compared to T8-Fz connectivity.
Δ high alpha connectivity
When examining Δ cross hemispheric (T7 vs T8) changes in frontal (Fz) connectivity, results from ANOVA showed no effect of time, F (1, 17) = 1.054, p = .318, ηp2 = .055. There was however a main effect of hemisphere, F (1, 17) = 4.751, p = .041, ηp2 = .232, and group, F (1, 17) = 4.977, p = .037, ηp2 = .217, which was superseded by a significant hemisphere x group interaction, F (1, 17) = 4.751, p = .041, ηp2 = .209. Follow up pairwise comparisons showed a significant difference between groups for T7-Fz connectivity (p = .022), in which the MT group exhibited a much greater increase from baseline compared to the GT group. The MT group also exhibited overall significant hemispheric asymmetry, with connectivity higher for T7-Fz compared to T8-Fz (p = .009), whereas the GT group did not (p = .906). Data for the transfer task can be seen in Fig. 7.