Can Reminiscing About the Past Make Us Less Impulsive?

Psychologists extol the virtues of reminiscing about the past. For example, gratitude interventions, which often involve writing about events that made you feel grateful, have been shown to decrease stress and increase happiness.

The most exciting thing about potentially being able to improve mental health by recalling positive memories is that people really like recalling positive memories. In a fascinating line of research, my collaborators Meg Speer and Mauricio Delgado found that people will actually pay to think about positive memories, especially if they are memories that include other people. Positive memory recall even increases activity in the reward system in the brain, and it buffers stress responses.

But can retrieving positive memories change decision making, too? For example, can reminiscing about the past make people more willing to delay gratification?

Let me explain why it might. You see, if you want people to choose larger, delayed rewards over smaller, immediate rewards, then the most effective intervention is to have people imagine a positive future event before they make the choice. When people are asked to envision where they might be in 6 months, and what fun things they might do then, they become more patient. It is also known that when we imagine the future in detail, we use our episodic memory system to do so. Perhaps, then, simply activating the episodic memory system by having people recall the past would be enough to reduce impulsive choices.

In order to test this hypothesis, I teamed up with Meg Speer, Mauricio Delgado, and my PhD advisor Elizabeth Phelps to see if recalling the positive past would lead people to delay gratification more. We asked people to think about positive memories (e.g., vacations, graduations, birthdays) before they made intertemporal choices, which are choices between smaller, sooner monetary rewards and larger, later monetary rewards (e.g., “do you prefer $20 today or $40 in 1 month?”). We found that people were indeed more willing to choose delayed rewards after recalling positive memories (compared to a control condition). This result was replicated by two other research groups, and it was consistent with one study showing that gratitude increases financial patience, too.

After grad school, I went on to do my postdoc with Joe Kable at the University of Pennsylvania. While I was there, I did a series of studies to learn more about how positive memory retrieval influences choice, and to see if we could strengthen the effect. At around the same time, other researchers in the Kable lab, including former grad student Trishala Parthasarathi, had been testing other, similar interventions, including a gratitude-based one.

The results of these follow-up studies were almost entirely null. In other words, we did not replicate the results of the experiment that I conducted in grad school.

So, what to do? If we didn’t publish the null findings of our follow-up studies, then everyone – including not just our fellow scientists, but also the public – would still be under the impression that reminiscing about the past is a reliable way to become more future-oriented. Therefore, we knew that we had to get the results out there, but unfortunately, null results are very hard to publish. Any one of the follow-up studies that we did would simply not be interesting enough or conclusive enough to warrant a scientific paper.

Therefore, we decided to conduct what is called an internal meta-analysis. To do this type of analysis, we gathered up all of the data that we (in this case, Joe Kable and myself) had that were relevant to the hypothesis. This included the studies that I did as a graduate student that were already published, as well as the studies that were done in the Kable lab that were unpublished. All together, we had done 14 studies (758 unique participants in total). When looking at all of these studies together, it was clear that positive memory recall simply did not reduce impatience. This was the case whether people were asked to remember generic positive memories, events that they were grateful for, or times that they were nostalgic for. We were able to publish this internal meta-analysis recently, so I can now feel confident that the scientific record has been set straight.

There are a few lessons to take away from this research. First, if you want to make decisions that benefit your future self, it’s more effective to imagine the future than to imagine the past. Second, there is certainly no harm in recalling the positive past; it still has many other benefits, and it never made people more impulsive.

Finally – and this is mostly for the scientists out there reading – don’t be afraid to revise your theories. It is said that science is “self-correcting” and that, over time, it becomes clear which findings are real and which are just flukes. But science will not self-correct if scientists are either afraid or unable to publish null findings.

When I think about doing all those studies, I feel gratitude. I am grateful to my original coauthors – Meg Speer, Mauricio Delgado, and Elizabeth Phelps – for taking a chance on this idea and giving me a lot of guidance. I am also grateful to my postdoc advisor Joe Kable for continuing this work with me and co-authoring the meta-analysis. That feeling of gratitude probably won’t make me a more patient person, but I am totally okay with that.