Each of the hats, which look like ordinary stocking caps, has enough "stretchability" to hold at least four heads in cold weather. Because heat causes expansion, only three heads fit comfortably in warmer temperatures, said Thomas Phillips, lead engineer in the hats' design process.

Despite the hats' name, there actually is no magic involved, Phillips admitted.

"Oh, goodness, no, it's not magic," Phillips said. "But our marketing researchers advised against calling them 'polybicarbonate myristic nylononsis hats.'"

Scientists involved in the project said they hope that the hats will encourage families to spend more time together.

Research was funded in part by a $1 million grant from the National Family Togetherness Council, a federal agency.

The scientific principles put to use in the hats may soon be used to create mittens and socks that will comfortably fit an entire family, Phillips said.

"We are very excited about the possibilities of eliminating single-person outerwear," Phillips said.

The hats, which are made in Taiwan and sell for $2.99 each, are distributed by the apparently "directionally challenged" East West Distributing Co. in Deerfield, Ill.