Correlations of Correlations Are Not Reliable Statistics: Implications for Multivariate Pattern Analysis

COUV_CAHIER_EGND_3by Bertrand Thirion, Fabian Pedregosa, Michael Eickenberg & Gaël Varoquaux

Representational Similarity Analysis is a popular framework to flexibly represent the statistical dependencies between multi-voxel patterns on the one hand, and sensory or cognitive stimuli on the other hand. It has been used in an inferential framework, whereby significance is given by a permutation test on the samples. In this paper, we outline an issue with this statistical procedure: namely that the so-called pattern similarity used can be influenced by various effects, such as noise variance, which can lead to inflated type I error rates. What we propose is to rely instead on proper linear models.

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