This paper reports on results of empirical research investigating written summaries of first-year Japanese university students, their task representations of summary writing, and the relationships between their representations and task performance. Data for this study were obtained by asking 108 students to read an English text and write a summary of it. Afterwards, the students answered survey questions which examined their task representations of English summary writing. The results reveal the following: 1) High copy rates with an average copy rate of 72.2% (SD 20.5%) were found, 2) Students did not seem to think that writing in their own words is required, 3) Students tended to look at the source text and use expressions from it in their summaries, 4) Positive correlations between copy rate and students' task representations regarding the use of expressions from the source were found, and 5) Negative correlations between copy rate and task representations regarding the use of their own words were also found. Though various sources of student plagiarism have been found and discussed in previous research, this paper attempts to propose task representations of summary writing as another possible source of excessive copying, which is regarded as plagiarism in English-speaking countries.