I was once chased out of a sushi restaurant in Manhattan for leaving a tip which was fine by UK standards, generous even, but low in US terms. It’s clear that tipping customs vary from country to country, but if you wait tables for a living could experiments buried in psychological journals hold some tips for you, on getting bigger tips?  

The size of the tip ought of course to be based on the quality of the service, but a review of 14 studies found that only rarely does quality have anything to do with it. Others factors make much more of a difference.  

Back in 1975 one analysis of restaurant diners found that the larger a group is, the smaller the tip. This research was conducted by Bibb Latane, the same psychologist who popularised the bystander effect, the idea (sometimes disputed since) that the more witnesses there are to an event such as someone being attacked in the street, the less likely anyone is to step forward to help.

Through an effect called diffusion of responsibility, each person thinks it’s not their job to help. In the case of a restaurant they think it’s not down to them to leave a decent tip because someone else in the group can do it. Having said that, it depends on the type of restaurant you’re working in. In one study, at the International House of Pancakes in Columbus, Ohio, the groups didn’t tip well – 11% tips compared with 19% at tables for one. But at the classier Smuggler’s Inn not far away, groups were just as generous as the singles and couples.

Waiters can’t control the size of the group they serve, but there are other things they can do in the hope of bigger tips

There is of course another reason why groups might sometimes tip less and that’s the shared bill effect. When you add up the money there’s never quite enough and so part of the tip is swallowed up to make up the shortfall. This is why so many restaurants add an automatic tip for larger parties.

Waiters can’t control the size of the group they serve, but there are other things they can do in the hope of bigger tips. An experiment conducted back in 1978 in a cocktail bar in Seattle found that simply smiling could more than double the tip. For this to work the smiling does of course need to appear sincere.

Likewise, a study at a restaurant called Charlie Brown’s in southern California, where half the waiters were instructed to introduce themselves by name at the start of the meal and half were told not to, the tips averaged 15% if there was no name, and 23% if there was.

The method of payment can also make a difference. People tend to tip more on credit cards. If you’re a waiter, then of course before you encourage your customers to do this, you need to be certain that the credit card tips get passed on to you by your employers. One intriguing, but unpublished study from 1995 suggests that as long as the customers have credit cards in mind, then even if they pay in cash, on average they leave more for service. Where credit card logos were visible, even though everyone in the study paid in cash, they added an extra 4% to their tip.

In more recent years some more obscure tactics have been tried. Two French psychologists Nicolas Gueguen and Celine Jacob have conducted many different studies on tipping. They’ve found that if waitresses wear red t-shirts, it makes no difference to the tips female customers give, but that men give more. 

This isn’t the first time that gender has come up these studies. Drawing a smiley face on the bill or writing thank you on the back has been shown to help waitresses, but not waiters, to get better tips.

If you ask someone to do something, they are more likely to say yes if you touch them on the arm at some point

Michael Lynn, a professor of consumer behaviour who has done a huge amount of work in this area does point out that smiley faces might not seem appropriate for fine dining. He suggests drawing a lobster on the bill might work instead. Quite a challenge for the harried waiter I’d have thought. Including a card with a joke on it alongside the bill can make a difference though. Or you could turn your attention, not to the bill, but to the shape of the dish on which it is served.  Heart-shaped dishes garnered more tips than round or square dishes.

If you’re feeling brave, Gueguen and Jacob discovered that a light touch on the upper arm also improved tips. Research from the 1980s had found that if you ask someone to do something, they are more likely to say yes if you touch them on the arm at some point. Whether you are asking them to lend you 10 cents, sign a petition or sample some free pizza, they say yes more readily.

A light touch appears to demonstrate what a nice person you are and that you are focussing all your attention on them. In the French study the unwitting participants were customers sitting alone in a bar in the town of Vannes, on the coast of Brittany. On that day only 10% of customers left something for service. But if the waitress briefly touched each customer’s arm as she asked them what they would like to drink, that rose to almost 25%.

I wish I’d know some of this research back when I was a waitress

So if you’re a customer and you notice the waitress is wearing a red top, introduces herself by name, beams at you, touches you lightly on the arm when she presents you with the bill in a heart-shaped dish accompanied by a smiley face and a card with a joke on it, while waving a credit card logo, perhaps she’s been studying the research. Of course no study has yet dared to try all these strategies at once to establish whether the effect of a 2% increase here and a 4% increase there is additive.

The difficulty is that although these studies did have control groups and had the advantage of being carried out in real restaurants rather than in a lab, meaning the ecological validity was high, in most it wasn’t possible to blind the waiters to the condition they were in. So they knew their job was to touch the customer on the arm or to smile winningly at them, which could have influenced their other behaviour too, leading to higher tips.

But I still wish I’d know some of this research back when I was a waitress. I did once get £20 for giving some parents a tiny bowl with a little profiterole to try each after their son refused to let them taste his. But that wasn’t something I’d have got away with very often.

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Claudia Hammond is the author of “Mind over money: the psychology of money and how to use it better”.

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