This paper examines the effectiveness of a visualization system for getting insight into future research activities from co-authorship networks. A co-authorship network is important information when doing a research survey. In particular, there are many requests on survey that relate with researchers' future activities, such as identification of growing researchers and supervisors. In previous paper we proposed a visualization system for co-authorship networks, which provides the function for identifying research areas and that for identifying temporal variation of both network structure and keyword distribution. This paper examines its effectiveness through field trials by test participants. The results are examined as the process of hypothesis verification, which shows that test participants could perform the task even though they had no background knowledge about InfoVis.