Written by Paula Brooks (PNI, G4)
Walking through your old high school might release a flood of memories that were locked away for years, perhaps even a decade (or more)! Walking through the cafeteria might remind you of the time you almost scared the timid new girl when you boldly walked up to her to invite her to join your friend group for lunch. Or maybe, going past the gym might bring back the memory of when you face planted in front of the entire class while attempting to do the high jump. (Full disclosure: Both of these things happened to me.)
It goes without saying that contexts—like an old high school cafeteria or gym—can trigger a flood of memories, including memories you thought were permanently gone. This phenomenon was coined more than 40 years ago as the “environmental reinstatement effect” and it is oftentimes explained by the following hypothesis: The more overlap there is between where a memory is formed and where it is retrieved, the easier it should be to successfully bring the memory to mind. Although this makes sense through the lens of the aforementioned anecdotal example, experimental evidence to support this hypothesis has been sparse. Why is that?
To be clear, context-dependent memory effects have indeed been demonstrated in controlled experiments. Famously, in 1975, psychologists D.R. Godden and Alan Baddeley conducted a study where they had people learn word lists either on land or while scuba diving. Then, they had people retrieve the word lists in an environment that was either the same or different from the one at learning. Godden and Baddeley’s manipulation showed a very strong environmental reinstatement effect: People remembered more words if learning and retrieval both occurred in the same environment, whether it was on land or underwater. However, as I alluded to above, this effect has been difficult to replicate in more traditional lab experiments where participants do tasks in front of a computer and contexts are differentiated using stimuli like different background colors on the screen. Does this mean that this phenomenon, which appears to have strong anecdotal evidence, is not robust? Not necessarily. Instead, the lack of experimental evidence for the environmental reinstatement effect might be caused by a gap between the contexts found in the real world versus in the lab.
A recent paper led by Dr. Yeon Soon Shin, who completed her doctoral degree in Neuroscience at Princeton University in summer 2020, and Rolando Masís-Obando, a 5th-year graduate student in Neuroscience, sought to tackle this very question. They hypothesized that having participants mentally represent and activate distinct areas of knowledge during learning and retrieval would help produce a robust environmental reinstatement effect. In other words, background colors on a screen might not elicit distinct enough contexts to see the environmental reinstatement effect. Instead, Shin and Masís-Obando, et al. used virtual reality to transport participants to two environments they assumed would activate already distinct areas of knowledge: the planet Mars and underwater. Although participants may not have any real-life experience in these environments (or at least that’s the case for the Mars environment!), they should still be able to activate distinct contexts when transported to these environments using VR because of prior general knowledge. For instance, going into the study participants should have known that Mars is the red planet in our solar system.
The cover story for their task was ingenious: Participants were pioneers scouting alternative places that people could inhabit in the future. Moreover, during their explorations, they encountered different words for items that they could either choose to keep because of their utility in that environment, or discard because they would not be as useful for thriving there. For instance, the word “vessel” might be deemed useful for carrying things on Mars, while the word “dress” might not be deemed useful. The purpose of this usefulness judgement was to encourage participants to process the words more meaningfully in the provided context, without making it explicit to participants that they will be tested later on.
Half of the participants learned the word lists in the planet Mars environment while the other half did so in the underwater one. After learning, participants either had no delay or a 24-hour delay before returning to the lab for a retrieval task. In this task, they were transported back to one of the two environments and had two minutes to verbally say as many words as they could remember. Half of the participants were sent back to the same environment they were in during learning, whereas the other half were sent to the other environment.
It is worth elaborating how the authors went to great lengths to make the two environments as distinct as possible. Not only did the environments look very different (look at the cover image for this article), but there were different background sounds associated with each of them. Furthermore, participants also had to physically interact with the environments in different ways. For example, in the planet Mars environment, participants had to engage with the environment by reaching up and scanning floating rocks using a portable handheld device to find words on the list. On the other hand, in the underwater environment, participants had to crouch down and open a treasure chest to reveal words. See the GIF below to see what this looked like.
After creating these distinct virtual environments, the authors were able to provide evidence for the environmental reinstatement effect. They showed that participants recalled significantly more items if the retrieval context was the same as the learning context. Unsurprisingly, fewer words were recalled after a 24-hour delay before retrieval, although it is important to note that the environmental reinstatement effect held for both time conditions. Interestingly, the environmental reinstatement effect was only seen for items that were deemed as being “useful” during learning, as compared to items that were categorized as being “not useful”. This might be because evaluating a word as being useful might lead to it being more strongly integrated with the specific context.
With this novel, high-tech paradigm, Shin and Masís-Obando, et al. were able to show that the seminal work by Godden and Baddeley can indeed be replicated in the laboratory (without the use of scuba divers!) if contexts are sufficiently rich and distinct, suggesting the validity of the environmental reinstatement effect. This study highlights the importance of bridging the gap between real world and lab-built contexts. These findings also suggest new avenues by which this effect can be more precisely studied in laboratory settings, such as making use of innovative new technology like immersive virtual reality.
So, if you ever want to take a walk down memory lane, you might want to consider going to the actual location of those memories. Even more, you might want to more meaningfully engage with your environment while you are forming a new memory to increase the chances that you will bring it to mind later!
When asked about what they were most excited about in regards to this line of research, Yeon Soon Shin and Rolando Masís-Obando replied: “It really is exciting to be doing research on the mind with VR. Without ever leaving the experimental room, we were able to transport participants to both an underwater and extraplanetary world! With VR, we can put participants in a good enough approximation of the real world, get naturalistic behaviors from the participants (who end up having fun!), and the best part, get really rich data.”
This article was published in Psychonomic Bulletin & Review in November 2020. Please follow this link to view the full version.