Memory Inhibition: Some Functions of Forgetting
People have always been intrigued by the topic of memory, and much research has been conducted in order to better understand the brain’s role in storing and recalling information. In fact, one of my very first science fair projects involved testing the short-term memories of my classmates. Our ability to remember certainly plays an extremely important role in our lives, affecting the decisions we make, and how we function in the world around us. However, I think that an equally important process, and one that is often overlooked, is that of forgetting.
We have all experienced various types of forgetfulness in our daily lives. These episodes are most often minor (such as forgetting where we have left our keys or forgetting to study for a test) or temporary (sometimes, when I am reading, a simple, everyday word will appear unfamiliar to me, but then I will recall its meaning a few seconds later). However, we are also aware of conditions such as amnesia (a loss of memory usually caused by a physical event such as a blow to the head or a stroke (7)) that can greatly impact a person’s ability to function. Furthermore, memory inhibition can have significant effects on processes that may not be immediately associated with forgetting, such as the experience of psychological disorders, or the acquisition of new languages (1,4). I first started thinking about my brain’s ability to forget certain information when I began studying my third language.
I am currently taking elementary Spanish at Bryn Mawr. Many of the students in my Spanish class (including myself) had no prior experience with the language, but had studied French extensively. From the first day of class, we found that we all had some level of difficulty learning words and phrases in Spanish, because we tended to want to say everything in French. As time went on, however, a new problem developed: I found that, as my Spanish improved, my ability to recall French words declined. And sometimes, I could not think of either the Spanish or the French equivalent of an English word. I found this entire situation to be fascinating (as well as confusing) and I started to wonder: how exactly might memory inhibition, or forgetting, be involved in the study of languages?
One study by Benjamin Levy and Michael Anderson suggests that people who are learning a new language may actively suppress knowledge of their native language. In this study, college-age native English speakers who were learning Spanish were shown objects. They were asked to repeat the Spanish names of these objects and then, after some time, to say their English names. Those students who spent more time repeating the Spanish words had greater difficulty recalling the English equivalents (1). This phenomenon of forgetting one’s native language can occur to varying degrees, depending on the situation, and is perhaps most easily observed in children who move to a different country at a young age and gradually replace their native tongue with the language of their new home; the process is referred to as “first language attrition.” (2).
What is the neurological basis for language attrition? Many people have heard that a person’s ability to learn a new language is greatly reduced at some point around age 13. A study by Dr. Paul Thompson at UCLA has provided support for the hypothesis that adults and children learn languages differently; in his study, MRI technology was used to view the brains of children and adults during language acquisition. The images showed that adults and children were using different areas of the brain to learn language. Children used the “deep motor area” of the brain, which is associated with more automatic, unconscious behavior, suggesting that language skills acquired as a child are more natural and automatic. Adults, however, stored new language information in other, more active regions of the brain. It has been suggested that when adults read or speak a new language, they do so by performing a conscious word-for-word translation from their native language (3). The need for this active translation, combined with the possible inhibition of previous linguistic knowledge, could explain why college-age students have such difficulty during the initial stages of learning a second, or third, language.
There are also some interesting psychological aspects to memory inhibition. It is obvious that the brain “chooses” to commit only some pieces of information to memory, or at least to make some memories more readily available than others. If this was not the case, we would remember every single thing that happened to us every day. Numerous experiments have demonstrated the human brain’s ability to remember pieces of information processed under varying conditions. However, can a person consciously make himself or herself forget something? When might such an ability be useful?
One fairly recent study at the University of Pennsylvania looked at directed forgetting in patients suffering from obsessive-compulsive disorder v. people with no apparent mental disorder. The goal of the study was to either disprove or provide further support for previous findings which indicated that OCD patients had more difficulty forgetting negative information. In this study, participants watched words appear one by one on a computer screen, accompanied by directions to either remember or forget the word. Words belonged to different categories, based on connotation (positive v. negative) and relevance to OCD (relevant/nonrelevant). Afterwards, the participants wrote down all of the words that they were able to remember. Although not all measured results were significant, OCD patients did seem to have increased difficulty in forgetting negative, personally relevant words when compared to the other test subjects (4). As someone with both a personal and family history of OCD, I find these results to be particularly interesting.
A separate study at Stanford University used fMRI technology to observe human brain activity during directed remembering and forgetting activities, and found that different areas of the brain were recruited during these two distinct processes. In the study, participants memorized pairs of words. Then, they were shown one word from each pair and instructed to try to either remember or forget the second word. Finally, a test was administered to see which word pairs each participant had actually memorized. The fMRI images showed that, as people consciously tried to forget words, the left and right frontal cortexes were more active, while the hippocampus showed decreased activity. The hippocampus was typically more active during the process of remembering. Although I was a bit skeptical as to whether or not this experimental design could work (I suspected that if participants focused on forgetting a word, their concentration would actually backfire and cause them to remember it) the final test showed that participants did indeed have the most difficulty remembering words that they had tried to forget (5).
So, the brain has the ability to consciously prevent certain pieces of information from being remembered. But, does this inhibition function by preventing information from being added to short term/long term memory altogether, or just by blocking our access to it? Is it possible for “blocked” memories to be “unblocked”? These questions become particularly relevant when we consider the highly controversial topic of “repressed” memories. Some people claim to have blocked memories of traumatic events (usually from childhood), which they were subsequently able to “retrieve”, often through some kind of therapy. Can such memories really be reliable? Since recalled information has been used as evidence in court (ex: in cases of alleged child abuse (6)), it is very important that more research be done to determine whether or not retrieved memories are accurate.
In conclusion, there is much that can be gained from studying the process of memory inhibition. Forgetting is proving to be yet another useful function of the nervous system, and one that can impact how we think, learn, and function as individuals, as well as how we interact as a society. My research into the topic of forgetting has generated far more questions than it has answered. Furthermore, I doubt that anything I have learned will help me to keep my languages straight. However, my exploration has helped me to develop a “less wrong” view of the brain’s role in memory processes, and I feel like that is at least a good start.
1) http://www.sciencedaily.com/releases/2007/01/070118094015.htm, “A New Language Barrier: Why Learning A New Language May Make You Forget Your Old One,” ScienceDaily, January 18, 2007
2) http://www.cal.org/resources/digest/involuntary.html, “Involuntary Language Loss Among Immigrants: Asian-American Linguistic Autobiographies”, Leanne Hinton, University of California, Berkeley, December 1999
3) http://www.acfnewsource.org/science/learning_language.html, “Neuroscientists have discovered why children excel at learning languages”
4) http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V5W-45WFS4G-4&_user=400777&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000018819&_version=1&_urlVersion=0&_userid=400777&md5=de0aa4ce1147f6a2afef647802247a3d, “Directed forgetting in obsessive-compulsive disorder: replication and extension,” David F. Tolin, Constance Hamlin, and Edna B. Foa, Behaviour and Research Therapy, July 2002
5) http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2004/01/09/MNG6C46SQ01.DTL, “Brain is built to forget, research says MRIs in Stanford study show active suppression of memories,” Science, Keay Davidson, January 9, 2004