David Avery was heading into his ninth round of the computer game "Playing in the Dark" when the mental lightbulb blinked on.

"I got it! I got it!" he shouted.

Four games later, Avery had handily drubbed his opponent by 50 to 21 points after having figured out the game's winning strategy of selecting strings of paired numbers.

Winning in this case means more than just the $5 cash prize that's typically paid out to the victors. The real winners at UCLA's new California Social Science Experimentation Laboratory (CASSEL) are the social scientists who are using this facility to conduct experiments in game theory to shed light on the inner workings of such aspects of human interaction as altruism, auction behavior and securities pricing.

The $2-million, 70-computer lab that opened last fall in 2400 Public Policy Building is the largest facility of its kind in the world, a state-of-the-art lab currently being used by experimental economists who were the first to embrace game theory. But following in their footsteps will be anthropologists, sociologists and political scientists.

"Playing in the Dark" goes beyond virtual fun and games. It opens a window for researchers to find out just what drives a competitor to explore strategies that benefit both him and his opponent.

These "games" have real-world applications. Similar computer-generated markets with real cash prizes have been used to design federal auctions of air space for digital phones, iron out details of the utility and airline deregulation and figure out cost-sharing plans for public broadcasting affiliates. Even jury reform efforts have benefited from this experimental approach that is gaining popularity among social scientists.

"Up until five years ago, you wouldn't have found an experimental economist at a top-ranked university outside of Caltech, which pretty much dominated the field," said David Levine, a UCLA economics professor and founder of CASSEL. "Today, experimental economics is still a small field, but it's growing pretty rapidly."

The lab, which was partially funded by a $825,000 grant from the National Science Foundation, is being launched at UCLA in collaboration with Thomas Palfrey, Caltech professor of economics and political science and one of the world's leading experimental economists. Palfrey runs a similar but smaller facility, the Hacker Social Science Experimental Laboratory at Caltech. However, the pool of available student research subjects there is limiting.

So the CASSEL lab, which can draw on UCLA's 35,000 undergraduate, graduate and professional students, will link with the Caltech lab, giving researchers there access to more than double the number of potential subjects.

The CASSEL lab also connects with a nearby classroom equipped with 50 PCs. Funded through an effort led by the Business Economics Council and the College of Letters & Science's Instructional Enhancement Initiative, the $500,000 Business Economics Computerized Classroom expands the potential slots at UCLA for any gaming experiment to 120 people.

Some fortunate students may find these experiments entertaining as well as lucrative. A few subjects have left gaming ex--periments after more than an hour with several hundred dollars in their pockets.

"We are creating artificial worlds where real financial windfalls are at stake," Levine said. "When hard, cold cash is on the line, you get a clear picture of how people interact."

UCLA scholars and administrators can take a look at the new lab March 7 at 4 p.m. at an open house hosted by Levine, a specialist in game theory, and Avery, the lab's manager.