DES MOINES, Iowa — Are cramped chickens crazy chickens? Researchers are trying to answer that question through several studies that intend to take emotions out of an angry debate between animal-welfare groups and producers.

At issue are small cages, typically 24 inches wide by 25 1/2 inches deep, that can be shared by up to nine hens. About 96 percent of eggs sold in the U.S. come from hens that live in the so-called battery cages from their birth until their egg-laying days end 18 to 24 months later.

Voters in California approved a proposition last year that bans cramped cages for hens. And Michigan's governor signed legislation last month requiring confined animals to have enough room to turn around and fully extend their limbs.

Peter Skewes, a Clemson University researcher, is leading one of the studies, funded by the U.S. Department of Agriculture, comparing how housing affects egg-laying hens. He said there are plenty of opinions about whether the cages are inhumane, but few are based on facts.

Bruce Friedrich, a spokesman for People for the Ethical Treatment of Animals, said banning the cages is a solution to an obvious problem.

“Think about the … effects of not moving for up to 24 months,” Friedrich said. “Their bones and muscles waste away and they go insane.”

Producers claim caged hens are healthier and satisfied with the only lives they've ever known. Although the chickens can't fully extend their wings, producers contend they're not stuffed so tightly they can't move around the cage.

“Is this animal cruelty? This absolutely is not,” said Bob Krouse, an egg producer in Mentone, and president of the United Egg Producers industry group.

Producers began experimenting with cages in the late 1950s. By the early 1970s, cages were commonly used for egg-laying hens and are now the standard home for hens, which can lay up to 300 eggs a year.

Skewes will compare emotional and behavioral patterns of caged hens with non-caged ones.

Another study, coordinated by the University of California at Davis and Michigan State University and funded by the American Egg Board, weighs several issues, including caged chickens' welfare and impact on the environment and human health as well as food quality and safety.

Dr. Gail Golab, director of the veterinary association's Animal Welfare Division, said she hopes the studies can clarify the debate.

“A number of us (who) work in the animal welfare field are frustrated at efforts to say one system is all good or all bad and not being able to quantify welfare values,” Golab said. “(We want to) look for the best possible solution we can for raising these animals.”