They can be deadly.
Even a distraction that lasts only two seconds can double the number of errors made while performing a series of tasks that must be done in a precise sequence, like preparing an aircraft for flight or performing surgery, according to new research from Michigan State University and the U.S. Naval Research Laboratory. If the noise lasts four seconds, the number of errors triples.
"There are a lot of tasks that we do in the world every day, like maintenance procedures, medical procedures and so forth, that have a sequential component, where you do one thing and then you do the next thing," psychologist Erik Altmann of Michigan State said in a telephone interview. He is the lead author of a study in the current issue of the Journal of Experimental Psychology: General.
Altmann and his coauthors, Gregory Trafton of the Naval lab and Zach Hambrick of Michigan State, put nearly 300 undergraduates through a series of experiments to determine whether distractions can cause serious errors when they are performing mental tasks that are challenging, but easily within the reach of any literate adult. The research confirmed what the trio had expected -- while distractions did not cause errors in the performance of particular tasks, they seriously degraded people's ability to follow a precise sequence of tasks.
Each task took two to three seconds, Altmann said, and "you couldn't just do it automatically. You have to think a little about the stimulus on the computer screen in order to make a response." That was the easy part. But even the ringing of the researcher's cellphone was enough to cause an increase in errors -- not in the tasks, but in the sequence of the tasks.
After an interruption, participants were more likely to forget where they left off, thus repeating one task they had already completed, or skipping one they had not done.
"If I add sugar twice to something I'm baking, it doesn't really matter," he said. "But if I give a diabetic an extra shot of insulin, that matters."
The Navy funded the research because performing difficult tasks in a precise sequence is often critical in the military.
"People who work on equipment for the military follow procedures, that's what the military does," Altmann said. "Procedures all share this sequential component."
What the evidence clearly shows, he added, is that a worker can do everything right but leave one thing out, or repeat the same thing twice, and that could lead to disaster. An ace fighter pilot who checks everything before taking off, but doesn't check to see if the plane really was refueled because he or she was distracted by a flock of birds overhead, may be in for a very unfortunate surprise after the jet clears the runway.
So what are we supposed to do about it? Altmann says there are common-sense steps that can be taken in many situations to reduce the number of distractions. Leave the cellphones outside, for instance, or at least turn them off.
"This is a silly lab task," Altmann said after the experiment, "so the errors don't cost very much. But in the real world, they might."