We’ve all had that experience of going purposefully from one room to another, only to get there and forget why we made the journey. Four years ago, researcher Gabriel Radvansky and his colleagues stripped this effect down, showing that the simple act of passing through a doorway induces forgetting. Now psychologists at Knox College, USA, have taken things further, demonstrating that merely imagining walking through a doorway is enough to trigger increased forgetfulness.

Zachary Lawrence and Daniel Peterson divided 51 students into two groups. One group spent a minute familiarising themselves with a large, furnished room. The other group wandered round the same room, but this one was divided in two by drapes, with a doorway connecting the two separated areas.

Next the participants were shown an abstract swirly image, and asked to remember it as they closed their eyes and imagined walking from the podium to the piano in the room they’d just experienced. For the second group only, this imagined walk meant passing through the room’s doorway (but the walk was the same distance as the other group’s). After imagining the walk in the room, both groups had to pick out the image they’d been shown earlier from an array of ten alternatives. The group who’d imagined passing through a doorway performed worse at the task than the first group who didn’t have to go through a doorway.

This result fits with the Event Horizon Model, which explains the forgetting effect of doorways in terms of the fact that we divide our memories into distinct events, that doorways trigger such a division, and that more forgetting occurs across event boundaries than within the same event. The new study shows that this event division effect can occur in our imagination and doesn’t require literally seeing a doorway and passing through it.

The first experiment wasn’t without issues – for example, the doorway group spent more time imagining their walk than the other group. Lawrence and Peterson conducted a second experiment in which two more groups of students were first exposed to a basic virtual reality room on a computer screen. One group saw a room with a partition and doorway; the other group saw the same room with no partition or doorway. Both groups were asked to imagine making a walk through the scene they’d been shown. This time both groups took the same time to complete their imagined journeys. But again, the group who imagined passing through a doorway performed worse when attempting to remember an abstract image they’d been shown before the imagined walk (roughly 18 per cent worse, which is comparable to the effect found for actually walking through a doorway).

“That walking through a doorway elicits forgetting is surprising because it is such a subtle perceptual feature compared to the rich environment in which it sits,” the researchers said, “that simply imagining such a walk yields a similar result is even more surprising, particularly when compared with actually walking through doorways.”

This effect of an imagined spatial boundary on forgetting is consistent with a related line of research that’s shown forgetting increases after temporal or other boundaries are described in narrative text. It seems real-world influences on your memory also apply in imagined realms, whether they’re of your own creation or someone else’s.

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Lawrence, Z., & Peterson, D. (2014). Mentally walking through doorways causes forgetting: The location updating effect and imagination Memory, 1-9 DOI: 10.1080/09658211.2014.980429

—further reading—

How is autobiographical memory divided into chapters?

How walking through a doorway increases forgetting

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.