By: Helen Beilinson
As we all know, a good night’s sleep is necessary to maintain normal function and to prepare our bodies for the demands of day-to-day life. Without proper sleep, we are more likely to feel groggy or depressed, be more susceptible to becoming sick, and are more likely to develop chronic diseases, such as obesity. Outside of these more disease-preventing functions of sleep, it has also been shown that sleeping promotes learning and recollection of events. In particular, sleep plays an important role in our ability to consolidate our memories. Neuronal traces of memories are reactivated during sleep in order to strengthen these memories and provide them with long-term stability. It’s kind of like our brains replay while we sleep what we saw, smelled, heard, etc. while we were awake in order to instill it in our memory.
Rapid eye movement (REM) sleep is the most beneficial phase of sleep for memory consolidation; it’s also the phase where you experience the most dreams. During REM sleep, exposure to odors associated with a particular experience can enhance the reactivation and consolidation of specific memories. For example, if you were studying wearing a particular perfume, smelling that perfume during REM sleep reminds your brain of what you were studying that day, as the smell and the facts are associated. After waking up, trying to remember those particular facts becomes easier, particularly if you smell the particular perfume. Scientists have recently shown that a similar phenomenon exists for sounds. One can imagine that by using either olfactory or auditory triggers while we sleep, we can learn new things, or, as a recent paper in the journal Science explored, relearn things in a different way.
Gender biases, particularly the association of women with art and men with science, are a form of memory, as are racial biases that associate people of color with negative words over positive ones. The authors of the aforementioned paper asked whether one’s intrinsic gender and racial biases could be altered using auditory cues during REM sleep. The researchers in this study investigated whether such gender or racial biases could be during sleep.
To do this, pictures of men and women of different racial groups were shown next to either science or art words, as seen in the figure below (from Science). Participants were asked to choose counterbias pairs- men with art terms and women with science terms. When these pairs were seen, participants pressed a button. A correct counterbias association would cause the program to produce a sound. Thus, when they saw a picture of a woman with a science word and reacted in a timely manner, a sound was made. When they saw a picture of a woman with an art word, no sound was made.
After this initial “training”, participants were invited to take a 90-minute nap. Once participants entered REM sleep (which you can distinguish as your eyes make rapid movements during this phase), the authors played the sound that was associated with counterbias pairs to half of the participants. Participants took bias exams both after they woke from their naps and a week after, to see whether they gained or lost social biases. In both cases, participants were more likely to correctly associate counterbias pairs, such that they were more likely to match women with science-related words or those of color with positive words. They only observed this significant change in those participants that were exposed to the sound while sleeping. Those that weren’t exposed didn’t show any changes in their biases.
So what does this all mean? First, it’s pretty cool that sound alone can change how a person thinks. This, of course, has Brave New World caution tape all over it. Manipulation of human thinking is an ethical issue that needs to be taken into account, in research and otherwise. This study also raises the question of whether or not their experiments are truly a test of social bias, or just adept picture/word matching. Many questions remain, but the study does open a lot of new doors. For example, auditory therapy could potentially be used in the treatment of posttraumatic stress disorder (PTSD). The benefits of such therapies could outweigh its costs, but ethical considerations must always be taken into account.