I got results from a cortical area analysis that intrigued me: Upon the inspection of clusters that survived Monte-Carlo simulation, I found a cluster with larger area among a first group in contrast to a second group. 

However, when I calculated the cortical areas means from that cluster (as available in the glmdir), the second group had values slightly larger than the first group (i.e., showing a difference in the opposite direction).

How would you explain such findings? Must I have committed a mistake in the analysis or its interpretation?

Best,

Pedro Rosa - University of São Paulo - Brazil.