To test the second and third assumptions that the pre-test tasks did not suffi-ciently deplete self-regulation resources and that all participants may have been de-pleted equally on the letter-crossing task, data were collected from control groups for the Stroop colour word (N = 65), OSPAN (N = 29) and ISR (N = 56) tasks. These participants were administered the pre-test and post-test administrations of one of the outcome tasks and spent 15 minutes talking with the experimenter instead of com-pleting the letter-crossing task. The assumption of the control condition is that talk-ing is not as cognitively demandtalk-ing as the letter-crosstalk-ing task and therefore should not deplete self-regulation resources. Repetition effects should be greater under the control condition if depletion transfer effects occurred from the letter-crossing task to the outcome tasks under the experimental condition. Pre-existing differences be-tween experimental and control groups may or may not exist at pre-test, any differ-ences should be magnified at post-test if depletion effects are to be observed in the data set.
A 2 (Group: Experimental, Control) x 3 (Subtask/Items: Word-Reading/ 2-Syllable, Colour-Naming/ 3-2-Syllable, ) x 2 (Session: Pre-test, Post-test) mixed method ANOVA was run for Stroop colour word and ISR tasks. A 2 (Group: Experi-mental, Control) x 2 (Component: Words, Maths) x 2 (Session: Pre-test, Post-test) mixed method ANOVA was conducted for the OSPAN task. Figure 6.7 shows the pre-test post-test differences for selected conditions in the three tasks. These three se-lected conditions were considered to be more critical of the task components. The colour-word naming subtask on the Stroop colour word task (Golden & Freshwater, 1978) is the only incongruent condition under the task measuring inhibition. The word component under the OSPAN task (Turner & Engle, 1989) did not achieve ceiling effects on the pre-test, unlike the maths component, therefore this component allowed space for observing repetition effects between experimental groups. The 4-syllable items under the ISR task presented as the most difficult under the ISR task from word length effects, once again allowing possible repetition effects to be ob-served. Other conditions in each task showed similar patterns.
The series of post-hoc ANOVAs confirmed that the interaction between group and test session was not statistically significant, F (1, 162) = 1.04, p = .309, MSE = 64.09, partial η² = .01, F (1, 172) = .30, p = .298, MSE = 6.64, partial η² < .01, and F (1, 163) = .25, p = .615, MSE = .02, partial η² < .01, for the Stroop, OSPAN, and ISR outcome tasks respectively. The current experimental design relies on the assumption that the control group required no self-regulation resources for conversing with the experimenter for 15 minutes. As such, there is no direct evidence that the conversa-tion was less depleting than the letter-cancelling task and it is not at all clear how such an assumption could be empirically tested. The lack of difference between the two groups suggests that depletion transfer effects did not occur between the letter-crossing task and the pre- and post-test executive functioning tasks. In short, experi-mental and control groups showed the same strength of repetition effects across the three tasks. The results of these analyses are consistent with the conclusion than the accuracy measure of the letter-crossing task is not a good measure of the depletion of self-regulatory resources.
Stroop Colour-Word OSPAN Word ISR 4-Syllable
Figure 6.7. Mean proportion (y-axis) scores across pre- and post-test sessions (x-axis) for a representative subset of tasks. Error bars were created from standard error values.
Something for future consideration is the distractor response measure. The distractor group by session interaction, representing the functional marker of deple-tion effects, was found under the OSPAN and ISR tasks. On face value, distractor re-sponses (i.e., responding to ei combinations) represent an obvious failure of the task goal in self-regulation, which suggests that this may be a more appropriate measure of depletion effects. While the distractor responses have face validity for self-regula-tion in the letter-crossing task, it is not clear how processes under the outcome tasks involves self-regulation, such as the ability to recall items in their correct order under the ISR task. In the PI-ISR task, which requires the regulation of responses by re-calling the target instead of the foil and there is some face validity for common self-regulation across tasks, the distractor group by session interaction did not emerge.
The second problem is that the interaction did not replicate consistently across the tasks used in the experiments. Distractor responses on the letter-crossing task are the most promising predictor for finding depletion transfer effects on outcome tasks, but the evidence for their utility needs to be explored further.
Therefore, in general these findings are not supportive of the strength model of self-regulation. The absences of depletion transfer effects in majority of the cur-rent results reflect the difficulty in reproducing the depletion effect that underpins the replication crisis facing the depletion literature. While Study 2 revealed that overall accuracy measures under the letter-crossing task were related to the executive func-tioning tasks, thereby suggesting a shared processing capacity between the two
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mains, the current study’s findings suggest that letter-crossing performance is not re-lated to self-regulation. This suggests that some form of executive functioning under-pins the letter-crossing task and cognitive outcome task used here, but these re-sources are not involved in self-regulation.
6.10. Summary of Chapter
The current chapter investigated the third functional marker of the strength model; depletion transfer effects from the self-regulation task to the outcome task.
While the letter-crossing task was correlated with the executive functioning tasks, performance on the letter-crossing task did not show depletion transfer effects. The lack of transfer depletion effects does not provide strong evidence for the strength model of self-regulation. The implications of these results will be discussed further in Chapter 7.
Chapter 7. Conclusions and Implications