Life is full of trading favors. We assist a colleague who is racing to meet a looming work deadline, or we babysit for a fellow parent in a pinch, or we help a friend move a piece of furniture—and then, eventually, we ask for something in return. But once we offer that favor, if we’re hoping for payback, how long should we wait before we make our request? Social mores seem to dictate that we let an appropriate amount of time pass before we make our move; if we ask too soon, we may come off as gauche. Maybe our colleague, fellow parent, or friend will think our initial act was purely instrumental, only taken to initiate a quid pro quo. But new work we published earlier this month in the Proceedings of the National Academy of Sciences suggests that if we want something done in return for our good deed, we cannot ask too soon.

We analyzed a setting where favor exchange is a billion dollar business: How a hospital that does its patients the “favor” of providing high-quality care can best time its requests for the “favor” of a charitable donation.  While this context may feel far-removed from the quid pro quo involved in exchanging favors with colleagues, friends and family, past research on reciprocity suggests the same principles likely apply.

Specifically, we analyzed data on over 18,000 donation requests made by a large university hospital system of its former patients.  These requests were all made by mail, after a patient’s first-ever outpatient visit to the medical center. To assess whether a speedy ask from the hospital for a donation from former patients was a good idea, we took advantage of a quirk in how donation requests were mailed to patients. Solicitations were sent in batches, so that all solicited patients who first visited the hospital in the same two-month window (for example, March or April of 2013) were sent letters on the same date. This quirk often leads to drastic differences in the time between a hospital visit and a donation request. For example, two patients of the same age, gender, and race who both visited the hospital’s oncology department one day apart could have completely different experiences with the hospital when it comes to receiving an ask for a donation. If the first patient just made a mailing cutoff that the second patient barely missed, the first would get her solicitation a few short weeks after her hospital visit while the second would receive it several months later. We asked: Does reciprocity decay over time or hold steady? Does asking for a quid pro quo backfire when you ask too early? 

What we find is a steep decay in people’s willingness to donate. For every additional month separating the provision of medical care from a donation solicitation, a patient’s likelihood of responding with a gift declines by 30 percent.  The drop-off is fastest for patients who visited hospital departments that tend to treat patients with the most severe ailments—the oncology, surgery, and cardiology departments.  This helps rule out the possibility that patients are just forgetting that they ever interacted with the medical center, as it’s unlikely oncology, surgery, and cardiology patients forgot about their visits.  The data includes some solicitations that arrive just days after medical care, and we see no evidence of backlash from sending the request for a return favor too soon. All evidence points to sooner being better.

What should we all make of this? What does data from a hospital system tell us more generally? We analyzed patients who received medical care, but their motivations for making a charitable gift to the hospital system that treated them are likely triggered by a reciprocal motive—a feeling of appreciation for what the staff, nurses, and doctors have done. This kind of reciprocity is at the heart of a wide range of our daily acts, from volunteering and charitable giving, to tipping, to favor exchange. While we analyzed data from a health care setting, the reciprocal motive that drives behavior is central to all these interactions. And while it has been typically assumed that willingness to reciprocate is fairly stable, we find evidence to the contrary. 

This is particularly important news for organizations that survive in part on donations from former recipients of services like hospitals, churches, humane societies, and schools.  Delays in their requests for donations turn out to be extremely costly.  But it is likely true for friends and colleagues as well.  We should not assume that a favor done will be returned with interest, but rather recognize that feelings of reciprocity fade quickly. If we aren’t being generous entirely out of the goodness of our hearts but instead harbor a hope that one good turn will earn another, we should not delay in asking for what we need back!

So, when you step in as a babysitter for a friend, ask them to be on duty for your next date night. When you pitch in to help a colleague with a project, do not delay in requesting their help in meeting your next deadline. And if you visit a hospital, do not be surprised if they ask you for a donation sooner than you might expect.