Newcomb's paradox (and Newcomb's paradox variants) get's discussed a lot here. But nothing from the poll indicates that kind of background knowledge is present among those polled. in fact, the opposite appears to be indicated, based on this link:

http://philpapers.org/surveys/results.pl?affil=All+respondents&areas0=0&areas_max=1&grain=fine

Newcomb's problem: one box or two boxes?

Insufficiently familiar with the issue 1254 / 3226 (38.9%)

That seems to be the problem with the greatest posted amount of insufficient familiarity among any of the posted philosophy problems. (When using the greatest population)

So I'm guessing that this factor in divergence may have to be accounted for.