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<p>This is for contributors to the <a href="http://www.psychologicalscience.org/index.php/replication" rel="nofollow">Registered Replication Report</a> for the ego-depletion component of the original experiment conducted by Sripada and colleagues:</p> <p>Sripada, C., Kessler, D., & Jonides, J. (2014). Methylphenidate blocks effort-induced depletion of regulatory control in healthy volunteers. <em>Psychological Science, 25</em>, 1227-1234. doi: <a href="http://dx.doi.org/10.1177/0956797614526415" rel="nofollow">10.1177/0956797614526415</a></p> <p>The <a href="https://osf.io/cx2nu/" rel="nofollow">approved protocol</a> was developed with guidance from Roy F. Baumeister, Chandra S. Sripada, and Daniel Kessler and this site includes the <a href="https://osf.io/cx2nu/" rel="nofollow">protocol</a>, <a href="https://osf.io/ifdj3/" rel="nofollow">materials necessary to conduct the study</a>, and the <a href="https://osf.io/4z9m8/" rel="nofollow">form</a> for laboratories who wish to join this registered replication project. </p> <hr> <p>Roy Baumeister & colleagues proposed an influential theory that performance on tasks requiring self-control is governed by a general, unitary, and finite ‘internal’ resource. The theory has broad implications, some of which are discussed in the bestselling book Willpower by Baumeister & Tierney. Engaging in tasks requiring self-control is thought to lead to the depletion of the resource and reduced performance on subsequent self-control tasks. Reducing self-control capacity is referred to as ‘ego depletion’. </p> <p>The classic evidence for the phenomenon comes from a simple and easily-replicable paradigm involving two consecutive tasks. For participants randomly allocated to the experimental (ego-depletion) group, both tasks require self-control while for participants allocated to the control (no depletion) group only the second task requires self-control, with the first task not requiring any, or very little, self-control. Self-control tasks typically require individuals to alter or modify an instinctive, well-learned response such as resisting impulses or overcoming temptations (Baumeister, Vohs, & Tice, 2007). Participants in the experimental group performed worse on the second task relative to participants in the control group. </p> <p>Critically, the tasks used in the experiments were from different ‘domains’ of self-control providing evidence to suggest that the resource was ‘domain-general’ and was implicated in all tasks that required self-control. Numerous replications of the original findings have supported this account. A recent meta-analysis revealed a medium effect size (d = 0.62) across 198 tests of the ego-depletion effect (Hagger, Wood, Stiff, & Chatzisarantis, 2010).</p> <p>However, some researchers have questioned the strength of the effect or whether the effect exists at all. A recent analysis conducted by Carter and McCullough (2013) suggested that the effect may be quite small or entirely an artifact of publication bias. They cite evidence that many tests of the effect were substantially underpowered suggesting that the likelihood of finding such a large number of significant effects in the literature is improbable. Although the interpretation of these analyses have been questioned (Hagger & Chatzisarantis, 2014), the issue of bias is a real one. Both Carter and McCullough (2013) and Hagger and Chatzisarantis (2014) recommend that large, pre-registered direct replications of the ego-depletion effect be conducted. </p> <p>This Registered Replication Report will do so using the paradigm developed and published by Sripada, Kessler, and Jonides (2014), which is very similar to that used in the original depletion experiments (Baumeister et al., 1998; Muraven et al., 1998), only using computerised versions of tasks to minimise variability across laboratories. This will make a unique contribution to the self-control literature by providing appropriately-powered replications of the ego-depletion effect across multiple laboratories.</p> <p>If you would like to participate in this project, complete the <a href="https://osf.io/4z9m8/" rel="nofollow">Secondary Replication Proposal Form</a> and submit it via the <a href="http://mc.manuscriptcentral.com/pps" rel="nofollow">Manuscript Submission System at <em>Perspectives on Psychological Science</em></a>. You can find the form and instructions under the <a href="https://osf.io/4z9m8/" rel="nofollow">How to Participate</a> Link (if you don't see it now, click on "Dashboard" above). If your proposal is approved, you will be added to this project and we will help you to create a linked project for your independent replication study. All completed replication studies will be published together in a single article at Perspectives on Psychological Science, regardless of their outcomes. All groups conducting replications will be expected to post the data from their study to their linked project page upon completion of the study.</p> <p>The protocol specifies the minimum requirements for participation (e.g., 84 participants/group), but we encourage those participating in this replication effort to use as large a sample as possible. Larger samples will provide a more precise estimate of the effect size, and smaller confidence intervals for each contributed study will lead to a better overall estimate of the effect size as well. Please specify your proposed sample size in your Secondary Replication Proposal Form.</p>
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