Google: the perfect crack machine

For humans, this desire to search is not just about fulfilling our physical needs. Panksepp says that humans can get just as excited about abstract rewards as tangible ones. He says that when we get thrilled about the world of ideas, about making intellectual connections, about divining meaning, it is the seeking circuits that are firing.

The juice that fuels the seeking system is the neurotransmitter dopamine. The dopamine circuits "promote states of eagerness and directed purpose," Panksepp writes. It's a state humans love to be in. So good does it feel that we seek out activities, or substances, that keep this system aroused—cocaine and amphetamines, drugs of stimulation, are particularly effective at stirring it.

Ever find yourself sitting down at the computer just for a second to find out what other movie you saw that actress in, only to look up and realize the search has led to an hour of Googling? Thank dopamine. Our internal sense of time is believed to be controlled by the dopamine system. People with hyperactivity disorder have a shortage of dopamine in their brains, which a recent study suggests may be at the root of the problem. For them even small stretches of time seem to drag. An article by Nicholas Carr in the Atlantic last year, "Is Google Making Us Stupid?" speculates that our constant Internet scrolling is remodeling our brains to make it nearly impossible for us to give sustained attention to a long piece of writing. Like the lab rats, we keep hitting "enter" to get our next fix.