Reciprocity Decay

Our desire to give back wanes rapidly with time

Conventional wisdom suggests that our desire to return favors doesn't fade over time. However, this fascinating new big data study suggests the opposite: that reciprocity has a a very narrow window and will quickly disappear.

Chuan, A., Kessler, J. B., & Milkman, K. L. (2018). Field study of charitable giving reveals that reciprocity decays over time. Proceedings of the National Academy of Sciences, 201708293.

"There is no human society that does not subscribe to the rule of reciprocity"

- Alvin Gouldner

From compliments to favors, giving gifts to loyal customers or asking social media influencers to Instagram that spicy ramen they just got for free, reciprocity is everywhere.

This uniquely-human IOU system unlocks a whole manner of transactions that allow for an efficient, specialized and prosperous economy.

Digging a little deeper into reciprocity psychology, we’re hard-wired to both give and give back, but we're also crucially obliged to accept. In accepting a gift, whether we wanted it or not, we're then motivated to remove the uncomfortable feeling of indebtedness that comes saddled with it.

And so the cycle continues.

Simply put, this uniquely-human web of indebtedness is crucial to the functioning of modern society and getting stuff done (Gachter & Hermann, 2009).

But reciprocity wanes...

And so we give, at least in part, in the hope of receiving something in return that we might need, perhaps at a later date.

But what if that time doesn't come? Conventional wisdom surely suggests that we will eventually get back what we put in, right?


New research just released by Chuan, Kessler and Milkman (2018) highlights, through a large field study, that if we don't trigger reciprocity within a given timeframe, the sense of obligation may be lost.

We may end up getting nothing at all.

In the following research, we explore how patients' desire to return a hospital's kindness with a charitable donation does indeed wane, and rapidly too.

The impact of this so-called 'reciprocity decay' for charities, marketing and loyalty teams is especially significant. But be warned: being too hasty might be just as bad as being too late. Our takeaways will explain how to time things just right.

The study

The study took place across eight university hospitals, taking data from 82,231 outpatient visits spread over a couple of years. Since the hospital system is funded in part by donations, 18,515 patients were sent a subsequent request for a financial contribution.

Based on the date of their first visit, patients were chunked into 2-month ranges and then all individually mailed a request at a pre-defined point, regardless of their personal visit date.

This last point is important, highlighted by an example below of how the mailing system would work for 4 patients within the Sep-Oct chunk.

An inefficient system like this is highly susceptible to reciprocity decay. What researchers found from looking at the donation requests was that patients' likelihood to donate significantly reduced as the time between their first visit and point of being asked for money increased.

Specifically, donation rates reduced from 1.5% down to 0.4%. Going further, delaying a request for donations by an additional 30 days reduced donations by a whopping 36%. And waiting 30 days til after a patient's last visit reduced donations by about 50%! Clearly, a significant and painful impact for any organizations dependent on some level of societal goodwill.

But why does our capacity to give back to others diminish over time? Well, researchers think a lot of it has to do with memory. Things that seem significant right now simply don't grab our attention in the same way that they might a year, a few months, or even a week from now. Life's Present Bias simply gets in the way. In this context, the discomforting threat to our own mortality has since waned. This medical challenge now overcome, new challenges - paying the bills, a new baby, moving house - these things take their place.

And we simply forget.

Though the study looked at charitable giving, reciprocity is critical in all areas of human interaction; from customer loyalty to workplace collaboration, this is the first major study that shows that our ability to return kindness wanes rapidly.

Simply put, we need to act quickly in order to benefit from reciprocity.


• Reciprocity and its subsequent decay are greatly dependent on how trivial or serious the initial act of kindness is. Burger et al (1997) found a faster reciprocity decay for strangers repaying the favor of being gifted a fizzy drink, for instance.

Key takeways

Don't wait too long to make your request. If you want people to respond to your requests, know that there is a ticking clock. Certainly, don't do what the hospital did and pre-define request dates. They've lost a lot of potential income by doing so. At the very least, send requests out more frequently. Better still, make the timing of reciprocal requests personal.

Don't be immediate, either. At the same time, requesting a knee-jerk reciprocal act, e.g. a waiter asking for a review on tripAdvisor at the end of the meal might not be the best time. If you have the diner's email, send them a request the following day, framed as a warm reminder of their evening. This may also allow them to 're-savor' the experience. Simply ask for their email at the end of the meal.

Trigger recall. If indeed you've waited too long to make your request, sending an initial correspondence that may help remind the recipient of the past act of kindness may be better.

Accommodate decay. This could be followed up shortly after by a request either framed in a more subtle fashion, or one that accommodates this decay and asks less of the recipient. For instance, a request to share a video of the organization's cause instead of a request for money.  

Draw a line. Strategically, if enough time has passed, assume that the likelihood of response - whether to an email you'd sent, your offer of collaboration or an invite to a dinner you were hosting - will be near zero. A fresh approach that entirely sidesteps any awkwardness of the delay may be your best bet. A smaller commitment request in an unrelated context will help reduce any discomfort on their part.

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  • Aspirational membership schemes and belonging The category size bias provides a credible explanation for why we human beings tend to associate with large groups that are viewed favourably by society. Being part of a large and “desirable” social group can make others believe that we also possess the many qualities of its members. For small businesses, it suggests that forming or being a part of a consortium or large and high quality networking group can dramatically elevate your brand image.
  • Communicating category sizes to nudge effectively Highlighting the differences between the large and small categories is highly likely to enhance the effect of the Category Size Bias. For instance, for software companies, stating that there are 10 features in the premium version versus 4 in the free version will help nudge a decision towards the premium version

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  3. We’ll spend or gamble more money on items put in larger categories.
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  5. We once we put something into a group, we perceive it to adopt all the characteristics of that group. This suggests that small companies should foster alliances with similarly-principled, more established companies.
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