You go out to eat. (Well, at least you used to.) The meal is great. The service is better. You're delighted. While a 15 percent tip is the theoretical standard, and 20 percent is much more common, you decide you'll leave 30 percent. 

Then the bill comes, and you realize an 18 percent tip is automatically included.

In theory, you should be happy: You enjoyed a great meal, received outstanding service, and saved a little money. (And, of course, you can always choose to add more to the tip amount.)

In practice, though, you're irritated.

And a lot less likely to return to that restaurant in the future.

The Rationale for Automatic Tips

Many restaurants automatically add 18 percent -- probably because 18 falls between 15 and 20 percent and the owners want to bump up the amount without seeming too presumptuous -- to parties of six or more.

But many restaurants have added automatic tips to every bill in an attempt to increase server income, decrease the odds of having to pay servers the restaurant's minimum wage, and increase tip-share income for greeters, kitchen staff, busboys, etc. 

Others want to, but have not. Three restaurant owners I spoke with said they would love to make tip income more predictable for their employees -- while clearly not in gross dollars, at least in terms of estimated amount per customer -- but have not implemented automatic tipping because they're afraid customers will resent not being able to "punish" servers for providing poor service. 

"The last thing I want to do is make customers feel like they have to leave a set tip amount," one told me, "especially if they're already less than pleased with the service they receive. That would only add insult to injury."

All of which makes sense. If I receive poor service and then have to leave an 18 percent tip ... Yeah, that's a double-negative experience.

But if I had an outstanding dining experience, research shows I'm even more likely to be unhappy with automatic tipping.

Delighted Customers Really Resent Automatic Tipping

Research recently published in Journal of Service Marketing shows that "Surprisingly, the negative effect of non-voluntary tipping was as strong (or stronger) under high (versus low) quality service."

Yep: Even though I'm delighted, non-voluntary tipping leaves me feeling worse.

We found that customers were equally frustrated by non-voluntary tipping -- this time because they couldn't reward their servers. Being able to reward the server makes customers feel good. That's part of the restaurant experience.

... their ability to show their gratitude has been blocked. They have fewer positive feelings about the restaurant experience, and they're less likely to eat there again.

While giving is usually considered selfless, giving can also be beneficial for the giver, as well as the receiver. (For example, providing social support may be more beneficial than receiving it.)

In short, we like to praise. We like to recognize. We like to reward.

Not because we have to, but because we want to -- because making other people feel good makes us feel good too. 

So while I'll be a little frustrated if I'm required to leave what I think is an excessive tip for an underperforming server, I'll be even more frustrated if you take away my ability to reward an outstanding server.

The net outcome for the server may be the same. But it's very different for me. I wanted to make someone else -- through my voluntary action -- feel good. I wanted to feel good.

And now I can't.

Which, science says, means that no matter how great the food and service, I leave with a bad taste in my mouth.

And will be much less likely to become a loyal customer.

Want to increase customer-discretionary income for your staff? Work hard to provide great products. Work hard to provide great service.

Do that, and customers will reward your employees.

Both now and in the future, because when you let customers decide how to reward your employees, they're much more likely to be repeat customers.