I reported the "coarse" results which lumps together "don't know," "insufficiently familiar to answer," and several others. Here are the fine data for undergraduates:

Newcomb's problem: one box or two boxes?

Insufficiently familiar with the issue 114 / 217 (52.5%) Lean toward: one box 22 / 217 (10.1%) Accept: one box 18 / 217 (8.3%) Lean toward: two boxes 18 / 217 (8.3%) Accept: two boxes 17 / 217 (7.8%) Skip 13 / 217 (6.0%) Agnostic/undecided 9 / 217 (4.1%) There is no fact of the matter 2 / 217 (0.9%) Accept an intermediate view 2 / 217 (0.9%) Reject both 2 / 217 (0.9%)