How thinking about the future can cause us to forget the past

We routinely envision future events, whether that be fantasising about next month's beach retreat, or planning whether to hit the gym this afternoon before or after picking up the dry cleaning. New research supports the idea that we are able to conjure up these "future" images by drawing on memories of past events. What's more, the experiments from University of Santa Cruz show that when future events take centre stage in our mind, it becomes temporarily harder to recall real, related memories.

Researchers Annie Ditta and Benjamin Storm gave 36 participants a topic, such as university accommodation, and asked them to come up with four different autobiographical memories related to that particular topic, in each case remembering for 15 seconds before summing it up with a simple title. Participants were also asked to generate future events related to six of the twelve topics. For university accommodation, one might imagine going back to an old residence for a party, or even dropping your future university-age children at their new place.

We know that memories can interfere with each other through an effect called retrieval-induced forgetting, where retrieving a memory to make it stronger has the side-effect of making related memories harder to access so as not to interfere with the currently relevant one. The question here is: does an imagined future event do the same thing – making it harder to remember the real, autobiographical memories related to that topic?

The data showed that yes, later on, participants found it harder to re-recall the autobiographical memories they'd described in the first session when those memories were related to a topic which had also been used to imagine the future.

Once the recall tests were over, participants were provided with all 48 of the titles they'd given to their memories (four items by 12 topics), and asked to bring each memory into mind and rate its detail, emotional intensity, and whether the perspective was first- or third-person. The future imagining had no effect on any of these things, suggesting that the memories may have been put out of mind, but their intrinsic content wasn't substantially altered.

Further experiments showed that this forgetting effect stands for both positive and negative personal memories, and that it generalises to non-autobiographical memories: recall of fictional events that participants learned about on the day were also suppressed by imagining topic-related future events.

The fact that something akin to retrieval-induced forgetting appears to be going on here supports the idea, developed from a range of past findings (e.g. people with memory problems often struggle to imagine the future), that future imagining actively draws from our existing memories. It's like an inventive team of scenographers setting up a Star Wars scene using the sets from Laurence of Arabia, the costumes from Yojimbo and the monster suit from The Blob. The authors speculate that this could matter in real life because our frequent imaginings about future possibilities may selectively strengthen the parts of our autobiographical memory network that directly line up with our hopes – or our fears – and leave related details in the dark.

Further reading

Ditta, A. S., & Storm, B. C. (2015). Thinking about the future can cause forgetting of the past. The Quarterly Journal of Experimental Psychology, (ahead-of-print), 1-12.