Just how little are students using e-mail these days? Six minutes a day, according to an experiment done earlier this year by Reynol Junco, an associate professor of library science at Purdue. With the promise of a $10 Amazon gift card, Dr. Junco persuaded students to download a program letting him track their computer habits. During the semester, they spent an average of 123 minutes a day on a computer, by far the biggest portion of it, 31 minutes, on social networking. The only thing they spent less time on than e-mail: hunting for content via search engines (four minutes).