Smell Ya Later: Odors, Sleep, and Memory
As anyone who has had a bad experience with tequila can tell you, smells conjure up memories better than any other sensation. Whether it is a late night of drinking, Mom’s cooking, Mom’s drinking, or the perfume of an ex-girlfriend, smells have a way of interjecting their way into a person’s life. This idea has made science headlines recently, as researchers have shown that scent cues have a beneficial effect on the memorization of certain kinds of facts. In a recent paper in the journal Science, a group of Germanresearchers demonstrated that the presence of a scent during both the learning process and during a particular stage of the sleep cycle had a major effect on the recall ability of the subjects the next day.
Over the past couple of years, researchers have shown a link between sleep and the ability to process newly acquired memories for long-term storage. Previous studies have shown that the hippocampus, the portion of the brain relegated to the memorization of daily activity, interacts with the cortex, the thinking and planning part of the brain, during slow wave sleep; a period of deep, dreamless sleep that occurs soon after the head hits the pillow and occasionally throughout the night. In the Science article, Rasch et al. studied the ability of subjects to remember the location of identical cards in a game of “Concentration”. They found that subjects were better able to retain the information about card location the next morning if rose scents were dispersed into the room during the memorization process and also during slow wave sleep. This advantage was seen only if the scent occurred during this particular sleep period, not if it occurred during REM sleep or while the subject was still awake.
In addition, they showed that scent cues were only able to help in declarative memory – roughly, the storing of fact and experiences. The ability of subjects to remember a series of finger taps, which requires a form of procedural memory not associated with the hippocampus, was not affected by scent cues during memorization or deep sleep. Importantly, applying a burst of scent – rather than having it be present continuously in the background – was imperative for the process to work. Anyone who has ridden a subway knows that the smell of urine is no longer noticeable after a few minutes due to a process of adaptation, and the authors reasoned that this same process eliminated the effect of lingering scents in their experiment. This should stop everyone from burning incense while they are pulling all-nighters. Believe me, it will do nothing but annoy your roommates and neighbors.
What this all means to those of us who memorize facts for a living is up to interpretation. Is it likely that students can use this technique to cram for a test the next day? Probably not, unless this same student has a method for determining what stage of the sleep cycle they’re in, and the ability to inject strong scents during both the learning process and during deep sleep. Nevertheless, the paper received a fair amount of press ranging from the New York Times to the Iranian Press TV for its potential practical application. The latter news source reported that pharmaceutical companies are researching drugs to help increase the length of deep sleep periods at the expense of REM sleep. While this is superficially a good idea, the importance of other stages of sleep is yet to be completely understood; they likely have other beneficial effects on performance.
Many of the articles in the popular press missed out on the most interesting aspect of this experiment: beyond the effects of smell on memory, this study supports existing evidence for the basic phenomenon of memory consolidation during deep sleep. If you want the most obvious and easily applied trick to studying, just make sure you get a good nights rest.
One question that showed up in some of the articles in the popular press (although not in the original publication) was whether different odors might be more or less effective at stimulating memory. Apparently there is some preliminary research suggesting that acrid smells may be more effective than the rose scents. While it’s anyone’s bet whether rose scented candles may start making an appearance in college libraries, a more effective prop might be an old gym sock. In the future, you might see pre-med students cramming for Orgo by systemically heaving their face in a bag of dirty gym socks stolen from the varsity locker room. The real go-getter students could even start bringing rancid meat in airtight containers. I hope for the sake of library workers everywhere, this technique remains in the lab setting. Could the next million-dollar idea be selling acrid smelling nasal sprays to college students complete with a scent-bursting device? All you need to do is reduce down the juice of a foul smelling vegetable and add some saline solution for the nasal spray. The scent-bursting device could be a high-powered air freshener with a timer or even a smoke machine. Hell, I could start producing this stuff in time for mid-terms! What am I doing in graduate school, anyway?
References
Carey B. 2007. Study uncovers memory aid: a scent during sleep. New York Times, March 9, 2007.
Familiar scent during sleep aids memory. Press TV March 11, 2007.
Study: Scents can help our remembrance of things past. USA Today, March 9, 2007.
SIN (Science in the News)
Too often, the media’s reporting on scientific findings and issues becomes a professional game of Telephone, with each re-telling adding an extra layer of misunderstanding, miscommunication, erroneous information, and dumbed down simplification. Each week, we will take a recent news story and attempt to excavate the original truth behind the hype, correcting the errors of the media’s coverage, commenting upon reoccurring issues with the science-to-public pipeline, and analyzing the motives and machinery behind these distortions.