We administrate the cognitive reflection test devised by Frederick to a sample of 483 undergraduates and discriminate the sample to consider selected demographic characteristics. For the sake of robustness, we take two extra versions that present cues for removing the automatic (but wrong) answers suggested by the test. We find a participant's gender and religious attitude to matter for the test performance on the three versions. Males score significantly higher than females, and so do atheists of either gender. While the former result replicates a previous finding that is now reasonably well established, the latter is new. The fact that atheists score higher agrees with the literature showing that belief is an automatic manifestation of the mind and its default mode. Disbelieving seems to require deliberative cognitive ability. Such results are verified by an extra sample of 81 participants using Google Docs questionnaires via the Internet.