WASHINGTON - Letter writers of yore had some of the same correspondence patterns as e-mail users today.

A new Northwestern University study of human behaviour has determined that those who wrote letters using pen and paper - long before electronic mail existed, did so in a pattern similar to the way people use e-mail today.

The study demonstrates the similarity of these two seemingly different activities, with the underlying pattern of human activity linking letters and e-mails.

Researchers examined extensive correspondence records of 16 famous writers, performers, politicians and scientists, including Einstein, Darwin, Sigmund Freud, Karl Marx, and Ernest Hemingway, and found that they sent letters randomly but in cycles.

They adhered to a circadian cycle; they tended to write a number of letters at one sitting, which is more efficient; and when they wrote had more to do with chance and circumstances than a rational approach of writing the most important letter first.

The same mathematical model the Northwestern team used in a previous study to explain e-mail behaviour now has been shown to apply to the letter writers.

This refutes the rational model, which says that people are driven foremost by responding to others. No matter what their profession, all the letter writers behaved the same way.

“We are interested in identifying and understanding patterns of human behaviour, in learning how we make choices,” said Lus Amaral, professor of chemical and biological engineering at the McCormick School of Engineering and Applied Science, who led the study.

“There are patterns to how we spend our days, and these models of probability, of how people allocate their time to do certain tasks, can be applied to many different areas.”

“People are not that rational,” added Amaral. “If a doctor, for example, better understands how we make decisions, he or she may be able to get better compliance with a treatment if it is tied to something a person does with regularity.”

The researchers studied correspondence that dated as far back as 1574 for Sir Francis Bacon and as recently, in the case of writer Carl Sandburg, as 1966, said a Northwestern release.

The letter data for the 16 individuals included a list of letters sent and, for each letter, the name of the sender, the name of the recipient and the date it was written.

These findings were published in Science.