A Conversation Stopper

The Gerald Ford Factor

If you can't walk and chew gum at the same time, science now serves up an explanation-dual-task interference. Our minds simply won't let us perform certain activities at the same time. No matter how simple.

Ever since 1940, it's been dear that two separate tasks calling for different responses could trip up ordinary mortals. One task might be labeling an object; the other, pushing a button depending on a sound's pitch. Researchers posited a "bottleneck"-the subject's response to the second task was upheld until the response to the first task was selected. No amount of practice could abolish the interference between responses, labeled the "psychological refractory effect." Unfortunately, until recently, psychologists upheld a response to this theory.

Enter Harold Pashler, Ph.D., associate professor of psychology at the University of California at San Diego. He has confirmed that when presented with two different tasks, we hold off our second response until the first response is chosen-regardless of whether or not the second stimulus is present. So expect problems the first time you walk and chew gum. You have to select walking before you can chew.

Why do we have such a hard time choosing responses to trivial tasks? Says Pashler, it's about our cognitive limitations. When we have to figure out a response, there's a delay. So how can you drive a car while debating politics?

Most of us no longer think about driving-it's " automatic," a series of preplanned actions. And the most complex are spaced out, tending to fall at the beginning and end of your trip-when there are, in fact, usually conversation lapses.

For Pashler, the evidence has important implications for the understanding of attention, or how people select for further processing one stimulus from the barrage of sensory inputs at any one time. Selecting and responding are two different things, and recent evidence suggests they are accomplished via different neural networks

The bottom line: When expected to perform two tasks, don't bother starting on the second before you've performed your first. And in the meantime, stay clear of first-time drivers looking for political debates.