What kind of emailer are you?

Do you send email only during the usual nine-to-five business hours, turning away from its ASCII lure in the evening? Or do you email people from the moment you wake up to the minutes before you climb into bed?

You're either one or the other, with no in-between category, says research from Northwestern University and Yahoo! Research, which examined the email habits of 125,000 university students in the U.S. and Europe to discover these "two worlds" of emailing habits.

Details on the research, which will be formally unveiled this summer, are scarce, but the logic of both groups isn't hard to see.

For some users, email is an extension of the office or the school day, and anything that comes in after hours can wait until tomorrow. For others, waiting is much too painful to put off for more than a few minutes. I put myself in the latter group: No matter what time it is, those boldface, unread messages scream out to be read, replied-to, and archived or deleted.

Lifehacker's poll on the topic has both types of users -- "day laborers" and "emailaholics" in a dead heat, with 50% of the population on each side of the fence. (As I write this, only 8 votes separate the two groups out of over 6,500 people answering the poll.)

So what about you? Do you email 'til the wee hours, or are you happy to shut off your PC when quitting time arrives?