Tradition holds that if a wishbone breaks evenly when pulled, both parties involved will get their respective wishes. Alternatively, if one party receives the longest part of the wishbone, then only that person's wish will come true.
The tradition of pulling a wishbone dates back to the Etruscans, who believed that chickens were oracles that could tell the future. However, they would simply pet the bones, and it wasn't until this custom was adopted by the Romans that the pulling of the wishbone began. The English then adopted the custom when they were invaded by the Romans and eventually brought it over to the U.S., where it has become tradition to use a turkey's wishbone instead of a chicken's.