In a report to the Army last year, Dr. Arkin described some of the potential benefits of autonomous fighting robots. For one thing, they can be designed without an instinct for self-preservation and, as a result, no tendency to lash out in fear. They can be built without anger or recklessness, Dr. Arkin wrote, and they can be made invulnerable to what he called “the psychological problem of ‘scenario fulfillment,’ ” which causes people to absorb new information more easily if it agrees with their pre-existing ideas.

His report drew on a 2006 survey by the surgeon general of the Army, which found that fewer than half of soldiers and marines serving in Iraq said that noncombatants should be treated with dignity and respect, and 17 percent said all civilians should be treated as insurgents. More than one-third said torture was acceptable under some conditions, and fewer than half said they would report a colleague for unethical battlefield behavior.

Troops who were stressed, angry, anxious or mourning lost colleagues or who had handled dead bodies were more likely to say they had mistreated civilian noncombatants, the survey said (PDF). (The survey can be read by searching for 1117mhatreport at www.globalpolicy.org.)

“It is not my belief that an unmanned system will be able to be perfectly ethical in the battlefield,” Dr. Arkin wrote in his report (PDF), “but I am convinced that they can perform more ethically than human soldiers are capable of.”

Image MORE ETHICAL? Ronald C. Arkin, a computer scientist at Georgia Tech, is designing software for battlefield robots. Credit... David Walter Banks for The New York Times

Dr. Arkin said he could imagine a number of ways in which autonomous robot agents might be deployed as “battlefield assistants”  in countersniper operations, clearing buildings of suspected terrorists or other dangerous assignments where there may not be time for a robotic device to relay sights or sounds to a human operator and wait for instructions.

But first those robots would need to be programmed with rules about when it is acceptable to fire on a tank, and about more complicated and emotionally fraught tasks, like how to distinguish civilians, the wounded or someone trying to surrender from enemy troops on the attack, and whom to shoot.