I appreciate that Ritchie et al., addressed my comment (made as a reviewer) regarding the fact that some subjects may have been aware that there was a surprise memory test and therefore explicitly/intentionally encoded the words. They say, "... the computer's random selection of words after the memory test meant that foreknowledge of the procedure should not have influenced the results in any particular direction." However, I don't completely agree with this statement and I still think there is a possibility that this aspect of the procedure could explain the null results. Whether words are incidentally vs. intentionally encoded influences the level of processing and can influence patterns of brain activation as well as behavioral outcomes. It seems plausible that if precognition relies on unconscious processing, that explicit encoding of the words could interrupt this (for example, consider verbal overshadowing, where conscious reflection can actually lead to worse performance on certain tasks).

As such, I think future work with this paradigm needs to find a way to address this concern either by directly manipulating whether the words are intentionally vs. incidentally encoded or by other methods (see Watkins, M. J., LeCompte, D. C., & Kim, K., 2000 for a discussion of this issue).

-Michael Franklin