The full results of the inferential tests mentioned in the poster.

Behavioural

Reaction time

A two-way ANOVA was conducted to examine the effects of age group, block, and their interaction on the dependent variable, reaction time. The results showed a significant main effect of age group, F(1, 32) = 35.73, p < .001, η² = .487, with a large effect size. The main effect of block was not significant, F(1, 32) = 1.84, p = .185, η² = .008. The interaction between age group and block was also not significant, F(1, 32) = 0.28, p = .597, η² = .001.

Comission error

Likewise, a two-way ANOVA was conducted to examine the effects of age group (young, older), block (first, last), and their interaction on the dependent variable, commission error. The results showed a significant main effect of age group, F(1, 32) = 18.99, p < .001, η² = .294, with a large effect size. However, the main effect of block was not significant, F(1, 32) = 3.74, p = .062, η² = .034. The interaction between age group and block was also not significant, F(1, 32) = 0.001, p = .972, η² <.001.

Inverse Efficiency

For confirmation, a two-way ANOVA was conducted to examine the effects of age group, block, and their interaction on the dependent variable, inverse efficiency. The results showed no significant main effect of age group, F(1, 32) = 2.91, p = .097, η² = .058. The main effect of block was not significant, F(1, 32) = 1.08, p = .307, η² = .011. The interaction between age group and block was also not significant, F(1, 32) = 0.20, p = .655, η² = .002.

Reaction times between blocks 8 and 9

There were 30 participants whose data was retain for neural analysis both in the main experiment and the motivational condition. An examination of difference between block 8 of the main experiment and the motivational blocked in these was undertaken to show differences on the same metrics.

A three-way ANOVA was conducted to examine the effects of age group, block, motivation and their interactions on the dependent variable of reaction time. There was a significant main effect of age group, F(1, 26) = 19.81, p < .001, η² = .418, with a large effect size. The interaction between motivation and block was also significant, F(1, 26) = 7.36, p = .01, η² = .016, with a small effect size.

Comission error between blocks 8 and 9

A three-way ANOVA was conducted to examine the effects of age group, block, motivation and their interactions on the dependent variable of commission error. There was a significant main effect of age group, F(1, 26) = 10.07, p = .004, η² = .236, with a large effect size. The interaction between age group and motivation was also significant, F(1, 26) = 6.78, p = .015, η² = .172, with a small to medium effect size. Inverse efficiency between blocks 8 and 9 A three-way ANOVA was conducted to examine the effects of age group, block, motivation and their interactions on the dependent variable of inverse efficiency. There was a significant main effect of block, F(1, 26) = 27.56, p < .001, η² = .271, with a large effect size. The interaction between age group and block was also significant, F(1, 286) = 5.28, p = .030, η² = .067, with a small to medium effect size.

Subjective scales

VAS

In a 2x2 mixed ANOVA testing the effect of age group (young, older) and time point (before, after) on the dependent variable VAS score, the results showed a significant main effect of age group (F(1, 32) = 5.03, p = .032), indicating a small-to-medium effect size, and timepoint (F(1, 32) = 45.75, p < .001), indicating a large effect size. However, there was no significant interaction between age group and timepoint (F(1, 32) = .69, p = .414).

MWS

Similarly, in a 2x2 mixed ANOVA, testing the effect of age group (young, older) and time point (before, after) on the dependent variable MWS-S score the results showed a significant main effect of age group (F(1, 32) = 5.61, p = .025, indicating a small-to-medium effect size, and timepoint (F(1, 32) = 16.80, p < .001), indicating a small effect size. However, there was no significant interaction between age group and timepoint (F(1, 32) = 2.20, p = .147).

Clusters

Time on task uncorrected cluster across all age groups.

We identified a cluster at a 0.05 alpha level (cluster statistic = 2599, P = < 0.001 [<0.001, <0.001]). The cluster occurred in the alpha frequency range (8-12 Hz) spanning the majority of the pre-stimulus time window. The cluster implied that an overall difference was present in the pre-stimulus window between the first and last block of the experiment in all participants.

Time on task uncorrected cluster across time between both age groups.

The highest identified cluster did not reach the alpha threshold (cluster statistic 7499.70, P = 0.065, [0.056 – 0.074]. Cluster across both age groups between the motivated and nonmotivated participants in the final block. The test failed to detected any clusters.

Time on task corrected cluster across all age groups.

We identified a cluster at a 0.05 alpha level (cluster statistic = 4899, P = < 0.001 [<0.001, <0.001]). The cluster mainly occured in the lower beta frequency range (14-24 Hz) a later post-task window (500-1000ms). The cluster implied that an overall difference was present in the post-task window between the first and last block of the experiment in all participants.

Time on task corrected cluster across time between both age groups.

The highest identified cluster did not reach the alpha threshold (cluster statistic 1385.50, P = 0.630, [0.613 – 0.647].

Pre-stimulus alpha power time on task effect confirmation

In a 2x2 mixed ANOVA, testing the effect of age group (young, older) and time point (before, after) on the dependent variable uncorrected alpha power (top electrode P5 in the -0.8 - -0.3s window at 8 – 12Hz frequency bands) the results showed a significant main effect of timepoint (F(1, 32) = 14.94, p = .007, η² = .007), indicating a small effect size. However, there was no effect of age group (F(1, 32) = 2.11, p = .157, η² = .061).

Post-task beta power time on task effect confirmation

In a 2x2 mixed ANOVA, testing the effect of age group (young, older) and time point (before, after) on the dependent variable corrected decibel-transformed beta power (top electrode in the 0.5 – 1.0s window at 14 – 24Hz frequency bands), the results showed a significant main effect of timepoint (F(1, 32) = 13.98, p < .001, η² = .058), indicating a small effect size. There was also a main effect of age group (F(1, 32) = 20.12, p = .001, η² = .35). However, the interaction between age group and time was not significant (F(1, 32) = 0.07, p = .796, η² < .001).

Pre-stimulus alpha power motivational effect

In a 2x2x2 mixed ANOVA, testing the effect of age group (young, older), time point (before, after) and motivational condition (demotivated, motivated) on the dependent variable uncorrected alpha power (top electrodes P5 and P7 average in the -0.8 - -0.3s window at 8 – 12Hz frequency bands), the results did not show any statistically significant relationship.

Post-task beta power motivation effect

In a 2x2x2 mixed ANOVA, testing the effect of age group (young, older), time point (before, after) and motivational condition (demotivated, motivated) on the dependent variable corrected decibel-transformed beta power (top electrodes C3 and FC6 average in the 0.5 – 1.0s window at 14 – 24Hz frequency bands), the results showed a significant main effect of age group (F(1, 32) = 16.34, p < .001, η² = .362). All the other effects and interactions did not reach statistical significance.

Reaction time skew

The uncorrected natural reaction times showed a skew distribution skewed towards the right 0.986, indicating a moderate skew. After a logarithmic transformation, the skewness diminished to 0.303, indicating an approximately symmetric distribution. For plotting, the reaction times are depicted in their natural unites (ms), but for modelling, the logarithmic version was preferred. As reaction time was used for computing inverse efficiency scores, its lower-skewness logarithmic version was used to compute the measure.