Multitasking Makes Us Dumber?

A number of studies have shown that attempting to multitask reduces performance to that of a person with a much lower IQ.

That's the topic of this interesting blog post over at MarketingProfs.

An excerpt:
There is a lot of excitement about staying up-to-date and making personal connections with new media tools and applications (think: Facebook, Twitter etc). However, in our attempt to multi-task and keep up to speed on everything we deem relevant, there’s a potential dark side—the dumbing down of our brains.

Based on Jon's post below about broadband in cars. . .does this mean that we're about to have even more stupid drivers on the road?