Eileen Wrigley can't put her finger on the latest hour that she's returned an e-mail from a student, but 3:30 a.m. is not outside the range of possibility. And midnight is a certainty.

For Ms. Wrigley, who teaches online courses in computer science at the Community College of Allegheny County, the Internet has completely changed her interactions with students.

"I'm a late bird, and if I'm up, I answer the e-mails," she said. "You become almost an individualized teacher."

But while most teachers don't e-mail into the wee hours, most college professors have changed their behavior to some extent as a result of the Internet -- be it posting a syllabus online or video-casting class lectures.

In some ways, the Internet has helped change the entire notion of a lecture class, with professors now breaking up lectures with images, sound clips and video.

These days, professors no longer fill the role as the supreme authority lecturing to a roomful of quiet subjects, said Anne Fay, director of assessments for Carnegie Mellon's office of technology for education. "There have been shifts from the idea that you stand up there and talk for an hour and 20 minutes and nobody asks questions."

In part, there's the belief that students of the multitasking, text-messaging generation simply can't -- or won't -- sit still and focus on one droning voice for an extended period of time. But there's also the hope that multimedia material can help students understand the material in another dimension.

Joseph Coohill, a history professor at Duquesne University, mixes up his "Shaping of the Modern World" class with images and video pulled from the Internet. For example, in discussing the origins of World War I, he shows a map of Austria-Hungary and then a video from the procession during which Archduke Franz Ferdinand was shot in 1914.

He's found that showing pictures and footage helps immensely in relating to students who grew up conceptualizing history as televised documentaries, but he takes care not to dumb down the material.

"Although I use technology a lot, I'm still giving them old-fashioned stuff," he said. "Just because I'm pandering to them with the technology doesn't mean I'm pandering to them with the material."

And there are many uses of technology where Dr. Coohill draws the line. He puts the syllabus, readings and handouts online using the Blackboard educational software, but he does not post detailed lecture outlines online -- fearing that class attendance would suffer if he did so.

To some extent, Dr. Coohill has tried to quantify the effect of his new teaching techniques, noting that students' test performance improved after he introduced the multimedia.

Other professors have conducted rigorous research into the effectiveness of Internet-based teaching tools. Kurt VanLehn, a professor and co-director of the Pittsburgh Science of Learning Center at the University of Pittsburgh, studied whether online homework-checking tools in an introductory college physics class made a difference in student performance.

He found that as long as students did the homework, online checking didn't seem to improve performance over paper-based systems. Nevertheless, he said, more sophisticated homework-checking programs could improve performance by correcting students at each step of the process, rather than just at the final answer.

"It gives them a hint just when they need it," said Dr. VanLehn, "just when they have the opportunity to learn what they don't know."

In a different format, Carnegie Mellon Professor Susan Finger also is using Internet technology to evaluate the processes of student thinking, rather than the final result.

Dr. Finger teaches civil-engineering-projects classes, in which students work on real or hypothetical design problems, such as redirecting storm-water runoff from a CMU parking lot.

To peek into the steps that the students are using to reach their solution, she created an online collaboration tool through which students can have discussions, schedule meetings and record work logs.

Dr. Finger then has all of that information at her disposal for grading purposes -- filling in a major gap in her previous evaluation system.

"One thing when you teach a design class is that most of the work happens in the group, and the professor isn't there when the group is working, so you don't know what the students are learning," she said. "Most of what happens in terms of learning is invisible to you."

But technology in the classrooms has its downsides as well.

Deborah Rubin, director of the social work program at Chatham University, likes using pictures and videos to enhance her lectures, and she posts supplemental materials online that her students might enjoy.

But she hasn't quite made her mind up about a classroom full of students using laptops. "Standing in the front of the room and having everyone looking down at their laptops can be a little disconcerting," she said. "I'm not saying it's a bad thing. I'm just saying it's distracting."

Professors also have to decide how much they want to police their students: Do they have a teaching assistant check what's on computer screens or do they let students make their own decisions about what they do during class time?

"My feeling is that it's their education," said Dr. Rubin. "I'm not sure that it's that different from daydreaming. Ultimately, you can either ban them or say that you're grown-ups, and if you choose to come to class and buy airline tickets, that's your choice."

While laptops are one big change over the last decade, Dr. Rubin sees increased professor accessibility through e-mail as an even more drastic shift in the way students and teachers interact. Students no longer have to wait around after class or come to office hours to get their questions answered.

And professors have to decide how to respond accordingly. Some, like Ms. Wrigley, make themselves available at all times. Others decide how to put limits on communication.

"Students are increasingly expecting their professors to be on call all the time," said Dr. Coohill, the Duquesne history professor. "I tell them that just because I'm e-mailable doesn't mean they're going to get an answer in five minutes."

At Chatham University, Dr. Rubin tells students that she will only answer e-mails during normal business hours. Sometimes she will write a reply to an e-mail over the weekend, but wait until Monday morning to send it.

"I'm happy to have people write me whenever they want to write me, and I want to be available, but there's an issue of boundaries and limits and professional behavior," she said.

Dr. Rubin also tries to use the e-mails as a teaching tool. As a professor of social work practice, she sees part of her job as making sure that students know proper professional behavior.

She makes sure to model professional etiquette by using proper language in her e-mails. And when she sees an e-mail address along the lines of "sexygirl@gmail.com," she urges the student to use her Chatham e-mail address for job and school-related matters.

Professors with the most experience with e-mail communications are those teaching online classes, who get to know their students exclusively over the Internet.

Sometimes, said Ms. Wrigley at CCAC, online classes enable her to have a relationship with students who wouldn't necessarily feel comfortable speaking in class, such as those who are shy or are non-native English speakers.

And since there's no appointed time for many or all of the class activities, teachers find themselves adapting to the students' schedules, rather than vice versa.

"Students expect you to be available 24/7," said Elizabeth Vargo, professor and director of CCAC's dietetic programs. "For the first time in all my years of teaching, I had to announce to them that I was going away and wouldn't be available on Saturday."