Comparing the test set perplexities in Tables 3  and 4, we can see the dependency bi-gram model achieves the same, or sometimes better performance of the original N-gram language models.
when we look at the tri-grams, the interpolated modified Kneser-Ney (KN) discounting method, which is state-of-the-art, shows its strength and our dependency model does not produce much improvement for the reasons we described above 18 .