Saving information on a computer boosts human memory resources for new information

.. but only when the storage medium is trusted
December 11, 2014

(Credit: iStock)

The simple act of saving something, such as a file on a computer, may improve our memory for the information we encounter next, according to new research published in Psychological Science, a journal of the Association for Psychological Science. The research suggests that the act of saving helps to free up cognitive resources that can be used to remember new information.

“Our findings show that people are significantly better at learning and remembering new information when they save previous information,” says psychological scientist and study author Benjamin Storm of the University of California, Santa Cruz.

“The idea is pretty simple: Saving acts as a form of offloading.  By ensuring that certain information will be digitally accessible, we can re-allocate cognitive resources away from maintaining that information and focus instead on remembering new information.”

The plus side of forgetting

Storm and Sean Stone, a former UCSC undergraduate student, were interested in exploring the interaction between memory and technology. While previous research had indicated that saving information on a digital device, such as a computer or camera, hinders later memory for it, the researchers hypothesized that there might be a positive flipside to this saving-induced forgetting.

“We tend to think of forgetting as happening when memory fails, but research suggests that forgetting plays an essential role in supporting the adaptive functioning of memory and cognition,” explains Storm.

In the first study, the researchers had 20 college students use computers to open and study pairs of PDF files (File A and File B). Each PDF contained a list of 10 common nouns.

The students had 20 seconds to study File A before closing the file. They then studied File B for 20 seconds and were immediately tested on how many nouns they could remember from the file. Only after this were they tested on their memory for File A.

Importantly, in half of the trials, the students were told to save File A to a particular folder after studying it. In the other half, they were simply told to close the file.

Just as the researchers expected, students remembered more words from File B when they had saved File A than when they had simply closed it. A second study with a separate group of 48 undergrads confirmed these results.

But the second study also revealed that the saving-related memory effects depended on how reliable the students thought the saving process was. When the students were told that the saved version of File A might not stick, that its contents might not actually be accessible, they showed no saving-related memory benefits. That is, when they thought saving was unreliable, students’ memory for File B was the same regardless of whether they saved File A.

“As technology develops, computers and smart phones are making it easier and easier to save information, which seems to have important consequences for the ways in which our memory functions,” says Storm. “By treating computers and other digital devices as extensions of memory, people may be protecting themselves from the costs of forgetting while taking advantage of the benefits.”

The researchers believe that the memory benefits of saving previous information may even have broad implications for how we think more generally:

“Coming up with a new idea or solving a problem often requires that we think outside the box, so to speak, and forgetting previous information allows us to do that,” says Storm. “By helping us to reduce the accessibility of old information, saving may facilitate our ability to think of new ideas and solve difficult problems.”

The limits to human memory storage

Ailin Moser, daughter of 2014 Nobel Laureates May-Britt and Edvard Moser, drew this picture of a house to illustrate how the method of loci works. If you wanted to remember the countries of South America, for example, you might imagine a seal playing a brass instrument in one room in your house to remember Brazil, and chili peppers in another room to remember Chile. (Credit: Image:Ailin Moser)

Which brings up the important question: what exactly is the upper limit to human memory storage capacity and how do we avoid mixing up similar memories?

To explore this issue, at least for events and places, a team of researchers in Norway and colleagues from the Czech Republic and Italy, headed by Norwegian University of Science and Technology (NTNU) Professor and 2014 Nobel Laureate May-Britt Moser*, tested the ability of rats to remember a number of distinct but similar locations. Their findings are published in the December 8 edition of the Proceedings of the National Academy of Sciences.

The brain creates and stores memories in small networks of brain cells, with the memories of events and places stored in a structure called the hippocampus.

The researchers tested memory in seven laboratory rats by letting them run around in 11 distinct yet similar rooms over the course of two days. The freely running rats wandered around the rooms in pursuit of chocolate crumbs while researchers recorded brain activity in CA3 place cells in the hippocampus. As their name suggests, place cells are neurons that fire in a specific place.

The rooms were very much alike, but the rats still managed to create a separate, independent memory, or a map for every environment, the researchers found. The researchers also found that when the animal was introduced to one of the rooms a second time, the spatial map from the rat’s first exposure to the room was reactivated.

“We investigated whether these memories overlapped across some rooms, but all of the memories were completely independent,” said the paper’s first author, Charlotte Alme. “This indicates that the brain has an enormous capacity for storage. The ability to create a unique memory or map for every locale explains how we manage to distinguish between very similar memories and how the brain prevents us from mixing up events.”

‘The method of loci’

Alme says their findings also help explain why a specific memory trick called “the method of loci” works. This technique involves making a connection between things that you want to remember and places that you know quite well. By associating individual memories with different rooms in your house, for example, you can more easily recall what you need to remember by mentally walking through your house and visiting each room.

“Our paper shows that rats (and most likely humans) have a map for each individual place, which is why the method of loci works,” she said. “Each place (or room in your house) is represented by a unique map or memory, and because we have so many different maps we can remember many similar places without mixing them up.”

However, Alme told KurzweilAI, “we do not know the limit of our memory capacity. We have no estimate although others have tried, based on the number of neurons in the brain.” One difficulty in making such an estimate is that “a personal memory is not a blueprint but rather a  dynamic reconstruction of what happened when and where. Memories change with time.”

* Moser, the corresponding author of the paper, mentioned the research in her Nobel Lecture on December 7 in Stockholm and said that the findings were important for understanding episodic memory, or memories that are formed from autobiographical experiences. May-Britt and Edvard I. Moser discovered in 2005 that other nerve cells in a nearby part of the brain, the entorhinal cortex, were activated when the rat passed certain locations. Together, these locations form a hexagonal grid, each “grid cell” reacting in a unique spatial pattern. Collectively, these grid cells form a coordinate system that allows for spatial navigation.

Abstract of Saving-Enhanced Memory The Benefits of Saving on the Learning and Remembering of New Information

With the continued integration of technology into people’s lives, saving digital information has become an everyday facet of human behavior. In the present research, we examined the consequences of saving certain information on the ability to learn and remember other information. Results from three experiments showed that saving one file before studying a new file significantly improved memory for the contents of the new file. Notably, this effect was not observed when the saving process was deemed unreliable or when the contents of the to-be-saved file were not substantial enough to interfere with memory for the new file. These results suggest that saving provides a means to strategically off-load memory onto the environment in order to reduce the extent to which currently unneeded to-be-remembered information interferes with the learning and remembering of other information.

Abstract of Place cells in the hippocampus: leven maps for eleven rooms

The contribution of hippocampal circuits to high-capacity episodic memory is often attributed to the large number of orthogonal activity patterns that may be stored in these networks. Evidence for high-capacity storage in the hippocampus is missing, however. When animals are tested in pairs of environments, different combinations of place cells are recruited, consistent with the notion of independent representations. However, the extent to which representations remain independent across larger numbers of environments has not been determined. To investigate whether spatial firing patterns recur when animals are exposed to multiple environments, we tested rats in 11 recording boxes, each in a different room, allowing for 55 comparisons of place maps in each animal. In each environment, activity was recorded from neuronal ensembles in hippocampal area CA3, with an average of 30 active cells per animal. Representations were highly correlated between repeated tests in the same room but remained orthogonal across all combinations of different rooms, with minimal overlap in the active cell samples from each environment. A low proportion of cells had activity in many rooms but the firing locations of these cells were completely uncorrelated. Taken together, the results suggest that the number of independent spatial representations stored in hippocampal area CA3 is large, with minimal recurrence of spatial firing patterns across environments.