Apple Store at The Grove in the Beverly Hills area of Los Angeles. Lines are still forming for the iPad 2. When the line gets too long, the store truncates it by moving most of the people about a block away.

Nothing succeeds like success. This maxim could be tweaked for the iPad 2 to nothing sells like success. That's the opinion of a consumer behavior expert who looked at how the chronically sold out iPad 2 works on the buyer's psyche.

People crave what they can't get--another maxim that applies here. Consumers would happily pay up front to reserve an iPad 2 at their local store. But they can't. Apple isn't doing the reservation thing this time. So, they wait in long lines (which, by the way, are still forming early every morning at Apple stores in Los Angeles, where I live. And also count me as falling prey to this psychosis.)

"Why would [Apple] deny my money and a for-certain sale"--Philip Graves, who has just published a book on the psychology of shopping, asks in a publicist's note sent out this week.

"Whatever the cause," Graves says, "here's why the iPad situation works psychologically:"

Heightened desirability: "It implicitly confirms the desirability of the item--it's a way of providing apparent social proof that this is a popular thing, and that's very attractive."

The adventure: "It creates discussion around each sale: suddenly buying one isn't just an acquisition, it's a story about serendipity or determination (or whatever)' humans love stories, and the excitement gets attributed (and misattributed) to the product."

Loss aversion: "Perhaps the biggest win is that, when a customer does come across one in stock, his purchase mindset is completely different. The unconscious mind is running a process to protect us a lot of the time (loss aversion)--it's trying to make sure we don't feel bad in the future. Ordinarily, with a regularly available product, the process is focusing on whether we could buy the item more cheaply elsewhere, whether we really want it badly enough, whether we might find a better alternative down the line. When supply is restricted (and you see the same thing in housing booms) the loss aversion is switched to fear that NOT buying the product will result in regret: when will you see one again if you don't grab it now You don't have the unconscious concern about finding one elsewhere because securing one at all is a result."

Wow factor: "In addition to all the other basic psychological drives that might cause us to want an iPad, you can add in or bolster several others because of the circumstances...now having an iPad (or iPad 2) has extra wow-factor, because it's less likely your friends will pull theirs out and say, 'Oh sure, I have one too.' People who have a strong competitive drive are also attracted to own one because it's a chance to be one up on other people.

The list price becomes a bargain: "Opportunists buy up stocks when they become available and sell them on auction sites like eBay. This creates the sort of price-skimming that retailers and brands could never get away with themselves (where the people with more money pay more because they can). Of course, people see this and you now have a price frame for the store item: people now see that they are getting an item that (some) people are prepared to pay $700 or $1,000 for, at the price of $499. All of a sudden the list price is a bargain."

The truth is, many people realize a lot of what Graves is saying and choose to ignore it. My advice: get in line, brother.