I think Nigel and Liz have established the two main reasons, but this surely does call for a prolonged and detailed programme of experimentation.
Before we start, could I just bags not being in the placebo/control group?
And whisky/whiskey; either's fine by me. As well as a Glenmorangie and some of the sweeter Speysides, I'm rather partial to a large Black Bush (as an ex will probably testify! Sorry - lowering the tone a tad)...