Multitasking Makes Workers, um... um... Dim Some.  
  Excerpted from PC Magazine TrendWatch, June 27, 2005  
  Messaging Haze

Does the constant barrage of e-mail, instant messages, and cell-phone calls hurt or help productivity? There are many ways to measure that, but a new study from England found strong evidence that constant interruptions reduce mental acuity. The study, commissioned by Hewlett-Packard, focused on 1,100 Britons and was conducted by TNS Research. As part of the research, Dr. Glenn Wilson, a psychiatrist at King's College London University, tracked the IQ of workers throughout the day in 80 clinical trials. He found that the IQ of those who tried to juggle messages and work fell by 10 points--more than double the 4-point fall seen after smoking marijuana.