<strong>Original citation:</strong> C McKinstry, R Dale, MJ Spivey (2008). Action dynamics reveal parallel competition in decision making. Psychological Science, 19.1: 22-24. <strong>Target of replication:</strong> We initially performed a power analysis on the second effect we decided to explore (of difference in curvature between high and low truth values). The original effect was measured paired t(140) = 6.0 p < 0.0001, prep > .999. After performing power analysis on these results using G*Power for a two tailed paired t-test and α = .05, 33 participants are needed for 80% power, 43 participants are needed for 90% power, and 53 participants are needed for 95% power. Subsequently, we decided that the key result was: "Sample entropy was higher for middle-truth-value questions than for low- and high-truth-value questions, quadratic r = -.70, F(1, 9) = 8.7, p < .05, prep=.939." However, because this result was reported as an item-wise statistic, it could not be used to deduce subject-wise power. <strong>Materials, Data, and Report Study materials</strong> can be found in the materials component of this project. Raw data and the analysis script can be found in the dataset node. The full report and other materials will appear in the files section of this node upon their completion. <strong>Conclusions.</strong> Replication of the primary result that sample entropy is inversely correlated to truth-value was successful. We demonstrated that medium truth values have significantly higher entropy than low or high truth values. Although the overall trend was the same, our data did not fall nicely into the same quadratic fit found by McKinstry et. al. However the correlation is still significant, and the differences between entropy for medium and the extremal truth values are at approximately the same magnitude. Additionally, the strong correlation of truth-values to average mouse movement demonstrates that the questions were accurately phrased for each truth value. We were unable to replicate the other claim in the paper regarding the curvature of the trajectories. This result does not seem directly linked to the key hypothesis, however, and may have been an exploratory finding of the original study. Overall, this study succeeded in replicating McKinstry et al.’s original study. Since the publication of this study, the authors have already replicated this finding themselves, including a conceptual replication using a Wii rather than a mouse (R. Dale, personal communication).