Google’s Multilingual Neural Machine Translation System: Enabling Zero-Shot Translation
Table 1: Many to One: BLEU scores on various data sets for single language pair and multilingual models.
['Model', 'Single', 'Multi', 'Diff']
For all experiments the multilingual models outperform the baseline single systems despite the above mentioned disadvantage with respect to the number of parameters available per language pair. One possible hypothesis explaining the gains is that the model has been shown more English data on the target side, and that the source languages belong to the same language families, so the model has learned useful generalizations.