Archive for December, 2009

Sleep Learning and Memory: A new approach?

Image by Sleep 1102 via Flickr

I have a long-term fascination with accelerated learning, including sleep learning and its variants – such as subliminal learning.  Researchers have claimed varying degrees of success with these learning approaches over the years, particularly in accelerated language learning, so when I came across a study that takes a fairly radical approach to sleep learning as an aid to memory I was immediately hooked.

Northwestern University researcher John Rudoy and colleagues recently published an article in Science (Vol. 326: 20 November, 2009) titled “Strengthening Individual Memories by Reactivating them During Sleep” that looks at the use of simple auditory stimulation to improve subjects’ recall of the spatial location of objects on a screen.  What is interesting about this approach is that it uses such a simple conditioned response technique to achieve a demonstrably effective outcome.  Previous attempts to use audio input during sleep to promote recall and learning have generally used an un-structured approach to the presentation of material.  Learning a second language, for example, was said to become easier if subjects played back low-volume tapes of the target language while asleep.  There is scant evidence that this approach is useful in accelerating language learning, or any type of learning, for that matter.  Jennifer Ackerman’s 2007 book “Sex, Sleep, Eat, Drink, Dream: A Day in the Life of Your Body” has the following to say about sleep learning. “… most scientists agree that learning during sleep – that is, actively acquiring new knowledge – is probably impossible. Certainly, attempts to teach slumbering adult subjects vocabulary or foreign languages or lists of items has failed miserably.”

Note that the study mentioned above doesn’t make any claims regarding learning as such.  Its focus is on promoting memory in the form of recalling the correct spatial position of objects, which is hardly a complex learning task.  Basically, the study showed subjects a series of graphic objects and placed them on a grid in specific locations. The placement was accompanied by a discrete sound that had some logical connection to the object.  A picture of dynamite, for example, was accompanied by a muffled explosion, a clock image had a ticking sound, etc. The 12 experimental subjects were presented with 50 object-sound pairs and asked to memorise the object locations. After some practice, they were then required to place objects appearing in random order in the centre of the screen into their correct locations on a grid.  Sound cues were not used during this time.  This constituted a pre-test for the experiment.

In the experimental phase the participants were wired up to EEG machines and asked to take a “nap” in a darkened room.  Once the EEGs determined that they were in deep sleep, 25 randomized sounds from the learning phase (equivalent to the most accurate object placements during the pre-test) were played at 5 second intervals. The “nap” phase lasted for at least an hour and participants were allowed to wake up naturally. Ten minutes later they were tested again using the same 50-object placement approach used in the pre-test.

The results were, predictably, quite significant.  The placement accuracy of the 25 objects whose sounds were used in the “nap” phase was  higher than the other 25 un-cued objects, to a statistically significant degree.  The researchers conclude that ” … reminders during sleep can be used to target the reactivation and strengthening of individual memories”.

Here’s a New York Times Science column by Pam Belluck which includes some dissenting views from other scientists researching sleep.

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