Stanford Center for Reproducible Neuroscience: A new preprint has been posted to the ArXiv that has very important implications and should be required reading for all fMRI researchers. Anders Eklund, Tom Nichols, and Hans Knutson applied task fMRI analyses to a large number of resting fMRI datasets, in order to identify the empirical corrected “familywise” Type I error rates observed under the null hypothesis for both voxel-wise and cluster-wise inference. What they found is shocking: While voxel-wise error rates were valid, nearly all cluster-based parametric methods (except for FSL’s FLAME 1) have greatly inflated familywise Type I error rates. This inflation was worst for analyses using lower cluster-forming thresholds (e.g. p=0.01) compared to higher thresholds, but even with higher thresholds there was serious inflation. This should be a sobering wake-up call for fMRI researchers, as it suggests that the methods used in a large number of previous publications suffer from exceedingly high false positive rates (sometimes greater than 50%).