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Like information in a book, unfolding events are stored in human memory in successive chapters or episodes. One consequence is that information in the current episode is easier to recall than information in a previous episode. An obvious question then is how the mind divides experience up into these discrete episodes? A new study led by Gabriel Radvansky shows that the simple act of walking through a doorway creates a new memory episode, thereby making it more difficult to recall information pertaining to an experience in the room that’s just been left behind.
Dozens of participants used computer keys to navigate through a virtual reality environment presented on a TV screen. The virtual world contained 55 rooms, some large, some small. Small rooms contained one table; large rooms contained two: one at each end. When participants first encountered a table, there was an object on it that they picked up (once carried, objects could no longer be seen). At the next table, they deposited the object they were carrying at one end and picked up a new object at the other. And on the participants went. Frequent tests of memory came either on entering a new room through an open doorway, or after crossing halfway through a large room. An object was named on-screen and the participants had to recall if it was either the object they were currently carrying or the one they’d just set down.
The key finding is that memory performance was poorer after travelling through an open doorway, compared with covering the same distance within the same room. “Walking through doorways serves as an event boundary, thereby initiating the updating of one’s event model [i.e. the creation of a new episode in memory]” the researchers said.
But what if this result was only found because of the simplistic virtual reality environment? In a second study, Radvansky and his collaborators created a real-life network of rooms with tables and objects. Participants passed through this real environment picking up and depositing objects as they went, and again their memory was tested occasionally for what they were carrying (hidden from view in a box) or had most recently deposited. The effect of doorways was replicated. Participants were more likely to make memory errors after they’d passed through a doorway than after they’d travelled the same distance in a single room.
Another interpretation of the findings is that they have nothing to do with the boundary effect of a doorway, but more to do with the memory enhancing effect of context (the basic idea being that we find it easier to recall memories in the context that we first stored them). By this account, memory is superior when participants remain in the same room because that room is the same place that their memory for the objects was first encoded.
Radvansky and his team tested this possibility with a virtual reality study in which memory was probed after passing through a doorway into a second room, passing through two doorways into a third unfamiliar room, or through two doorways back to the original room - the one where they’d first encountered the relevant objects. Performance was no better when back in the original room compared with being tested in the second room, thus undermining the idea that this is all about context effects on memory. Performance was worst of all when in the third, unfamiliar room, supporting the account based on new memory episodes being created on entering each new area.
These findings show how a physical feature of the environment can trigger a new memory episode. They concur with a study published earlier this year which focused on episode markers in memories for stories. Presented with a passage of narrative text, participants later found it more difficult to remember which sentence followed a target sentence, if the two were separated by an implied temporal boundary, such as “a while later …”. It’s as if information within a temporal episode was somehow bound together, whereas a memory divide was placed between information spanning two episodes.
Radvansky, G., Krawietz, S., and Tamplin, A. (2011). Walking through doorways causes forgetting: Further explorations. The Quarterly Journal of Experimental Psychology, 64 (8), 1632-1645 DOI: 10.1080/17470218.2011.571267
(via Research Digest)