<strong>Original citation:</strong> C Mitchell, S Nash, G Hall (2008). The intermixed-blocked effect in human perceptual learning is not the consequence of trial spacing. Journal of Experimental Psychology: Learning, Memory, and Cognition, 34.1 (2008): 237-242. <strong>Target of replication:</strong> Study 2: Performance on trials in which AX (or BX) was presented is expected to be better than that on trials in which CX was presented. A contrast relying on a multivariate, repeated measures model will be used to compare overall performance across the two types of the test (AX/BX vs. CX/DY). <strong>A priori replication criteria:</strong> A main effect of training condition (AX/BX versus CX). <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> We partially replicated the results observed by Mitchell and colleagues (2008). We find a similar main effect of same versus different trials, but no main effect of training condition (AX/BX versus CX). Instead, our data provided a tentative indication of an interaction between trial type and condition, with the benefit of intermixed presentation being present for performance on different trials, but not on same trials. The intermixed-blocked effect is aimed at examining how people learn to perceptually differentiate visual stimuli, which makes the performance on different trials the most important test of the theory. We can therefore conclude that even though we do not exactly replicate the overall pattern in Mitchell et al. (2008), our data on the different trials provides additional support for the most important theoretical prediction by the intermixed-blocked effect. Our observed effect size estimate is smaller than that in the original study, but confidence intervals in the effect size estimates overlap. ![enter image description here][1] [1]: https://osf.io/fksmt/?action=download&version=1