Wireheading
The practice of providing direct electric stimulation to the "pleasure center" of the brain. Lab experiments on lab rats showed that, when provided with a button that when pushed provided wirehead stimulation, the subjects would push the button in lieu of food, water, or anything else. Wireheading promises to be the purest, most addictive physical stimulation possible. Wireheading usually involves an invasive medical procedure, although (in theory) a created being could have a similar device.
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[Wirehead Hedonism]