Generally speaking, you cannot learn from sounds of new
information while you sleep, though this was a fad several decades ago. But in
an earlier post, I discussed a new line of research where sleep learning can occur. The key is to play sound cues
that were associated with learning that occurred during the previous
wakefulness period. The explanation I posted was that cue-dependent sleep
learning can work because a normal function of sleep is to strengthen memories
of new information and that presenting relevant cues during sleep increases the
retrieval of these memories and makes them accessible for rehearsal and
strengthening.
The latest experiment by a
different group shows that this cuing during sleep can modify bad attitudes and
habits. The test involved counter stereotype-training of certain biased attitudes
during wakefulness, and investigators reactivated that counter-training during
sleep by playing a sound cue that had been associated with the wakefulness
training.
In the experiment, before a
90-minute nap 40 white males and females were trained to counter their existing
gender and racial biases by counter-training. A formal surveyed allowed
quantification of each person's level of gender or racial bias before and after
counter-training. For example, one bias was that females are not good at math. Subjects
were conditioned to have a more favorable attitude about women and math with
counter-training that repeatedly associated female faces with science-related
words. Similarly, racial bias toward blacks was countered by associating black
faces with highly positive words. In each training situation, whenever the
subject saw a pairing that was incompatible with their existing bias they
pressed a "correct" button, which yielded a confirmatory sound tone that
was unique for each bias condition. Subjects were immediately tested for their
learning by showing a face (female or black) and the counter-training cue,
whereupon they were to drag the appropriate bias-free face on to a screen with
the positive word. For example, if the first test screen was that of a woman,
accompanied by the sound cue, the subject dragged a woman's face onto a second
screen that said "good at math." Results revealed that this
conditioning worked: both kinds of bias were reduced immediately after
counter-conditioning.
Then during the nap, as soon as
EEG signs indicated the presence of deep sleep, the appropriate sound cue was
played repeatedly to reactivate the prior learning. When subjects re-took the
bias survey a week later, the social bias was reduced in the sound-cued group,
but not in the control group that was trained without sound cues.
Experimenters noted that the
long-term improvement of bias was associated with rapid-eye-movement (REM)
(dream) sleep which often followed the deep sleep during early stages of the
nap. That is, the beneficial effect was proportional to the amount of nap time
spent in both slow-wave sleep and REM sleep, not either alone. It may be that
memories are reactivated by cuing during deep (slow-wave) sleep, but that the
actual cell-level storage of memory is provided by REM sleep.
Implications of this approach to
enhancing learning and memory show a great deal of promise. Can it be used for
enhancing learning in school? Can it be used in rehabilitation of addicts or
criminals? But there is a dark side. Now might be a good time to re-read
Huxley's Brave New World wherein he
actually described conditioning values in young children while they slept. Sleep is a state where people are
mentally vulnerable and without conscious control over their thoughts.
Malevolent people could impose this kind of conditioning and memory enhancement
on others for nefarious purposes. These
techniques may have valid social engineering applications, but they must be
guided by ethical considerations.
Dr.
Klemm is author of Memory Power 101
(Skyhorse), Better Grades, Less Effort
(Benecton), and Mental Biology
(Prometheus).
Sources:
Klemm, W. R. (2013). New discoveries on optimizing femory formation. http://thankyoubrain.blogspot.com/2013/05/new-discoveries-on-optimizing-memory.html
Hu, Xiaoqing et al. (2015. Unlearning implicit social biases
during sleep. Science. 348(6238), 1013-1015.
