You bump into somebody on the street. You recognize her face, but have no idea who she is. Is she your significant other’s sister or your old TA? After a few minutes of small talk, she gives you a cue that provides the context of how you met, and your mind floods with rich, vivid memories.
U of T neuropsychology researcher, Melanie Cohn, knows this situation well: “You say, ‘Oh, hi’…then a minute into the conversation you realize that you were their TA and you gave them a really bad grade!” Cohn was the lead author of a study that gave scientific insight into this phenomenon and provided important evidence for an ongoing debate in the neuroscience world.
Hippocampus 101
The great neuroscience debate is centered on the part of the brain called the hippocampus. If you’ve seen Christopher Nolan’s psychological thriller, Memento, then you already know about the effects hippocampal damage can have on a person. Guy Pearce’s character in Memento is incapable of creating new long-term memories. He has to rely on written notes, Polaroids, and body tattoos to make sense of the world because his memory periodically refreshes, leaving him completely unaware of what just happened. Pearce’s character was based on a man known as Patient HM, who had two thirds of his hippocampus surgically removed in an attempt to treat his epilepsy. HM lost the ability to permanently remember any of his post-surgery life events.
Cognitive psychologists call the memory of life events “episodic memory,” and see it as a process separate from “semantic memory”— or the knowledge of facts, such as the capital of France. Episodic memory is different because it requires a sort of mental time-travel. We can all rewind to moments in our past and relive them. Semantic memory does not require us to remember the context in which we learned the information. We just know it.
Neuroscientists encounter trouble when they try to pinpoint the function of the hippocampus. According to Cohn, there are two camps: one camp views memory as just one process involved with the hippocampus that can be graded from ‘strong’ to ‘weak.’ The other camp thinks that the hippocampus supports only “recollection and associations” or episodic memory.
Researchers in the U of T Department of Psychology, in association with the Krembil Neuroscience Institute at the Toronto Western Hospital, provided strong evidence in support of the latter camp.
How the study worked
The significance of Cohn’s study, which was published in December in the journal Proceedings of the National Academy of Sciences, is based on a simple idea: that the brain works the same with small episodes, such as recognizing a word, as it does with larger and more complex episodes, i.e. remembering a person.
Participants were asked to study a long list of 180 “novel word pairs” (pairs of words that don’t usually go together, such as “alligator chair”). For each pair, they were asked to think about how easy it would be to generate a sentence with the words, for example, “The alligator stole my chair.” Then they entered the MRI. They were given goggles and told to watch a computer monitor while the machine scanned their brain activity. The screen would display a word, and participants had to rate their confidence of having already studied the word on a scale from one to four, with a special fifth option, which meant not only did they study the word, but they had extra episodic memories associated with it (“I remember being in Melanie’s office and picturing a criminal alligator stealing a chair”). According to Cohn, the fun part came when a second word was displayed alongside the first word: “If they see the second word, then it might jolt their memory a little bit. They might be able to retrieve even more of the context.” Participants again had to make a decision about whether or not they had studied the word.
The Astonishing Results
For half of the displayed items, the presentation of the second word (the context) jolted participants’ memories, and they chose the fifth option. The critical finding of the study was that only the recognition of these words was associated with significantly greater hippocampal activity. Rated memory strength, on the scale from one to four, had no effect on the activity of the hippocampus.
Why it matters
If you, the reader, want to better remember this article, stop and take a look at your surrounding environment. Now think about your internal environment—what are you feeling right now? According to Cohn, you’ll be able to remember the information in this article better if you bring the context, using elements called “retrieval cues,” back into your consciousness. “Trying to cue oneself is a good strategy to try to remember any information,” says Cohn. What’s another scientifically proven way to encode this into your long-term memory? Try to really understand the material, and think about how it connects to things in your life—things that already exist in your long-term memory.
So the next time you run into somebody that you almost recognize, ask, “How do we know each other again?” or “Where did we meet?” This way, you indicate that you do recognize her, and are making an effort to remember her name. It won’t be a complete social faux pas, and she will probably forgive you. Also, according to Cohn and associates, you are much more likely to remember if you engage your hippocampus by considering the context of the time that you encoded this person into your long-term memory.
