He said our brains are not actually physically capable of handling multiple active tasks at the same time. Active tasks require attention. He said there are two types of multitasking: switch-tasking and background-tasking.

“Background tasking is where something mindless or mundane is happening in the background, that would be like running on the treadmill while you’re watching TV,” Crenshaw said. “That’s not really multitasking.”

He said in contrast, switch-tasking involves more active tasks like driving while talking on the cell phone or surfing the Internet while listening to a lecture. When we do two active tasks simultaneously, Crenshaw said, our brain under-performs because it is actually switching rapidly between tasks. Crenshaw said every switch incurs a switching cost, which equals lost time and effort

Chunking describes how human memory utilization works. It is important to remember this concept as we look at doing several tasks "simultaneously." We are in fact switching between them rather than doing them at the same time.

Multitasking was once heralded as a fantastic way to maximize one’s time and get more done in a day. Then people started realizing that when they had a phone in their ear and were making calculations at the same time, their speed and accuracy (not to mention sanity) suffered. Rather than multitasking, try a new strategy known as “chunking.”

Don't waste so much of your time trying to multi-task. Instead, make yourself more efficient and more productive by chunking. Set aside chunks of time for specific tasks Reduce the time spent in start-up moments Don't allow interruptions Increase the number and size of chunks during your day and week Recognize that there will still be interruptions no matter how well you chunk.

"Heavy multitaskers are lousy at multitasking... The more you do it, the worse you get," said Stanford communications professor Clifford Nass.

Compulsive media multitaskers are worse at focusing their attention, worse at organizing information, and worse at quickly switching between tasks, the Stanford scientists wrote.

After testing about 100 Stanford students, the scientists concluded that chronic media multitaskers have difficulty focusing and are not able to ignore irrelevant information.

Multitasking, when it comes to paying attention, is a myth. The brain naturally focuses on concepts sequentially, one at a time. At first that might sound confusing; at one level the brain does multitask. You can walk and talk at the same time. Your brain controls your heartbeat while you read a book. A pianist can play a piece with left hand and right hand simultaneously. Surely this is multitasking. But I am talking about the brain’s ability to pay attention… To put it bluntly, research shows that we can’t multitask. We are biologically incapable of processing attention-rich inputs simultaneously.

When most people refer to multitasking they mean simultaneously performing two or more things that require mental effort and attention. Examples would include saying we’re spending time with family while were researching stocks online, attempting to listen to a CD and answering email at the same time, or pretending to listen to an employee while we are crunching the numbers.

So there’s no such thing as multitasking. Just task switching – or at best, background tasking, in which one activity consumes our attention while we’re mindlessly performing another.

Even though the study did not revolve around interruptions from cellphones or other gadgets, one researcher said the results provide a “clear extrapolation” to the impact of a stream of incoming rings and buzzes. “Technology provides so much more of an interference than what we did here,” said the researcher, Dr. Adam Gazzaley, a neurologist at the University of California at San Francisco. Indeed, the paper argues that studies like this are becoming increasingly important as aging adults spend more time in a work force with heavy multitasking demands.

the research shows instead is a “diminished ability” to reactivate the networks involved in the initial task.

A growing body of research shows that juggling many tasks, as so many people do in this technological era, can divide attention and hurt learning and performance. Does it also hinder short-term memory?

When we talk about multitasking, we are really talking about attention: the art of paying attention, the ability to shift our attention, and, more broadly, to exercise judgment about what objects are worthy of our attention.

When people do their work only in the “interstices of their mind-wandering,”

their culture may gain in information, but it will surely weaken in wisdom.