On the other hand, it is important to stress upon the fact that the human written summaries were generated from external sources and written following an abstractive paradigm (i.e., they include material that is not explicitly present in the source documents), whereas our proposed method is an extractive one (i.e., it selects sentences from the source documents).
the chances to have common sentences between our summaries and the human-made ones decrease, as well as the corresponding ROUGE scores.