The most similar multimedia stimulation to the Internet is gambling. Internet addictions and gambling have a lot in common. You never know what you’re going to experience when you log on or when you gamble. Gambling addictions are likely to be a combination of the social aspects along with increases in dopamine, adrenaline, and other neurochemicals. The dopamine provides a sense of exhilaration, although shortlived, and because it is intense and pleasurable, can become habit forming. The brain will repeat experiences that are pleasurable. Normal life can seem dull compared to the excitement of the addiction “hit,” especially if the brain is bored. ( Greenfield, Daivid N., PhD. Virtual Addiction – Help for Netheads, Cyberfreaks, and Those Who Love Them. pp 22 -23. CA:New Harbinger Publications, Inc, 1999.)
David N. Greenfield, PhD, is the author of one of the largest and most comprehensive surveys on internet addiction. He is also author of the book entitled Virtual Addiction. (ABC News: Chat with Dr. David Greenfield.)
Refer to Video Games - Internet and the Brain for additional information.