The effect of “Vote with your tip: Cats or Dogs?”

Instead of just asking for a donation, turn it into an expression of one’s identity (e.g. are you a winter or summer person?). The technique increased tips by 136% in a cafe.

Today’s research is about increasing donations, rather than customer acquisition or profit.

It’s perfect if you’re an NGO or collecting support for a cause, but also if you want to boost the effectiveness of your CSR program or the income your employees make from tips.

Encourage prosocial behavior by making people choose between two ‘dueling’ choices

Impacted metrics: Donations
Channels: Customer experience | User experience

Tip type: Existing research (June 2020)
Previous tip: When people in your ads should look at the viewer - or away (All tips here)


Increase low-cost prosocial behavior (e.g. tips, donations, recycling, cigarette butt disposal) by asking people to make a choice that lets them express themselves (e.g. which football team they support, cats vs dogs).


  • Asking to express a preference between two ‘dueling’ choices using a donation is more effective than simply asking to donate. 

  • The two choices must be an opportunity to express preferences related to one’s identity (e.g. “I’m a beach [vs mountain] person”) - even if unrelated to the donation cause. A meaningless choice (e.g. A vs B) has no or little effect.

  • For example:

    • A ‘Cats vs Dogs’ duel tip jar more than doubled (136% higher) the amount of tips collected in a North Carolina cafe, compared to a normal tip jar

    • An online appeal to donate to the Red Cross increased the number of people that donated (54%) when it gave a ‘Chocolate vs Vanilla ice cream’ choice compared to when it didn’t (37.4%)

  • The effect works both in public (e.g. tipping jar) and private situations (e.g. anonymous online donation).

(Picture of the tip jars used in the cafe experiment - Click to zoom in)

Why it works

  • We love opportunities to express our identities. Donating a small amount is an easy way to do that.

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  • The researchers tested light-hearted preferences. You should probably stick to those too, without being too gimmicky or trivial in light of the cause. It’s unclear what would happen with choices related to political (e.g. pro vs anti Brexit), embarrassing, or private aspects.

  • It’s unclear what happens when there are more than two choices. Based on previous research, it’s likely better to limit it to two. More options could overwhelm and backfire.

  • The effect was only tested on small amounts (a few dollars or cents). It’s unlikely to work for large amounts (e.g. $100), although it might be possible if the dueling options are extremely significant for the target audience.

  • We don’t know if there are long-term positive or negative effects on brands or future donations. Some research found that when we mix altruistic acts with personal benefits we ‘taint’ the experience and become less prosocial in the future. Would expressing our preference have a similar effect?

Companies using this

  • Some cafes and restaurants in the US use this technique to encourage tipping. It’s rare in the rest of the world.

  • NGOs and company CSR programs don’t seem to be using this technique.

  • A handful of companies have innovated in this space, such as Ballot Bin which makes outdoor ashtrays with customizable choices and claims to reduce cigarette butt litter by 46%.

Steps to implement

  • Consider what choice options your audience would see as expressive. For example, it could be a light-hearted local rivalry between two towns or sports teams.

  • Try to change options regularly. Otherwise, people may feel they have already expressed their opinion and may not do so again.

  • Some of the contexts you could test applying this in:

    • Tipping at a bar

    • Online donations

    • Social media engagement (e.g. Which is better?)

    • Encouraging certain actions (e.g. Recycling bins with two drop options)

  • Once you understand what works, try thinking out of the box to apply it to new contexts.

Study type

Field, lab, and online experiments, United States


Rifkin, J. R., Du, K. M., & Berger, J. (June 2020). Penny for Your Preferences: Leveraging Self-Expression to Encourage Small Prosocial Gifts. Journal of Marketing.

[Link to paper]


Bloch School of Management, University of Missouri–Kansas City; Lubar School of Business, University of Wisconsin–Milwaukee; and The Wharton School, University of Pennsylvania. United States.

Remember: This research could be disproven in the future (although this is rare). It also may not be generalizable to your situation. If it’s a risky change, always test it on a small scale before rolling it out widely.

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