The day may come when you won’t have to figure out what 15 percent to 20 percent of your check is at the end of a meal, but the earliest experiments in eliminating tipping at American restaurants have proved to be less than conclusive.

In one closely watched case, Joe’s Crab Shack has decided to revert to accepting tips at most of its trial locations, six months after announcing that it would become the nation’s first major restaurant chain to test a no-tipping policy at 18 locations.

The casual seafood chain, which is based in Houston and has more than 130 restaurants nationwide, raised its menu prices at the test sites and said it gave higher, fixed wages to its staff. At the time, Ray Blanchette, then the chief executive of its parent company, Ignite Restaurant Group, called tipping “an antiquated model.”

But Bob Merritt, the new chief executive, announced in a conference call with investors and analysts last week that the company was cutting back the experiment and that it would continue at just four restaurants, according to Nation’s Restaurant News.