This explains why the combination works better than either feature on its own, but due to possible biases inherent in the makeup of the corpus, such as which female or translated authors are published and selected for the corpus, no conclusions on the influence of gender or translation should be drawn from these datapoints.
this is mitigated by the fact that fragments are extracted from pairs of folds, while selection is constrained to fragments that are attested and significantly correlated across the whole training set.