156 words from each of the pre-rated valence categories were shown to participants (leftmost column in 2a), but some were classified by participants as a different valence from the pre-rated norms. Because the extent of deviation from the pre-rated norms had a skewed distribution, the median number of categorizations is shown in Table 2a instead of the mean. A false positive was defined as a valence judgment that did not coincide with the pre-rated norms. A d′ score (shown here in 2b) was calculated for each person at each level of arousal for both the pleasant versus neutral and the unpleasant versus neutral boundary (omitting data from the third valence category in each case). Values are listed as “mean (standard deviation)”.