Instead, we examined people's ability to discern relative differences, because by varying the rating differences represented by the test instances, we can evaluate multiple granularities in a single experiment.
at intervals over a number of weeks, we authors (a non-native and a native speaker of English) examined pairs of reviews, attemping to determine whether the first review in each pair was (1) more positive than, (2) less positive than, or (3) as positive as the second.