Computing Lexical Contrast
Table 7: Pointwise mutual information (PMI) of word pairs. High positive values imply a tendency to co-occur in text more often than random chance.
['[EMPTY]', 'average PMI', 'standard deviation']
We calculated the pointwise mutual information (PMI) If two words occurred within a window of five adjacent words in a sentence, they were marked as co-occurring (same window as Church and Hanks \shortciteChurchH89 used in their seminal work on word–word associations). Observe that the high-contrast pairs have a much higher tendency to co-occur than the random pairs control set, and also the synonyms set. However, the high-contrast set has a large standard deviation. A two-sample t-test revealed that the high-contrast set is significantly different from the random set (p<0.05), and also that the high-contrast set is significantly different from the synonyms set (p<0.05).