The Effects of Sleep on Category Structure Knowledge
What is the role of sleep in preserving our memories of recently learned categories? Sleep is believed to facilitate memory consolidation, or the gradual process of changes in memory storage after initial encoding that are vital to preserving the memory. Research suggests that sleep is vital for abstraction and creative thinking, though time delays are also hypothesized to facilitate this process of generalization. How does one night of sleep impact our memory beyond what we would expect within the same timespan? Using a two-session design, this thesis addresses the effect of one night of sleep versus the same amount of time (12 hours) awake on memory performance on a feature association task.
We recruited 80 workers on Amazon Mechanical Turk to complete two sessions of a statistical learning task involving features of a new species of beetle. Counter to my hypothesis, sleep was not a statistically significant factor in overall accuracy scores for session two on either of the two category structures tested (ring structure with low modularity, and more clustered mod structure with high modularity). Thus, sleep did not preserve knowledge of category structures in a way that was significantly different from the same amount of time spent awake. However, in the ring sleep condition, knowledge of core structure was preserved, while memory performance decreased for peripheral features. This suggests that sleep may prioritize better encoded information (core knowledge) over modular structure when the category structure itself is harder to learn.
Comments
Hi Jayme, Sleep is so…
Hi Jayme,
Sleep is so important (and so under-rated!) that I'm always delighted to see data demonstrating that sleep helps consolidate learning. Nice job! I understand why you manipulated the two conditions the way you did (easy to do using MTurk), but I'm a little worried that time of day of learning and testing is confounded with sleep. It's possible that people simply learn better (at least core features) when they learn in the evening than when they learn in the morning. Another possible explanation is that when you learn something first thing in the morning, there is a lot more opportunity for interference over the rest of the day. It's REALLY hard to disentangle sleep from interference, because what control can you use to minimize interference that isn't being asleep? Doing nothing for a number of hours? That would be weird, and you'd never get people to do it. So the methodology of this sort of research is tricky. If you were to continue this line of inquiry, (imagine unlimited resources and being able to pay people to come in to the lab for hours at a time) what might you do to try to disentangle time of day and interference effects from the consolidating benefits of sleep?
Looking forward to seeing your response!
Cheers,
Dr. Hunt
Hi Jayme, Lots of questions!…
Hi Jayme,
Lots of questions! Did you ask people how much sleep they got? Was it similar across conditions? Maybe it isn't sleep as much as previous focused attention or something like that. Why would sleep prioritize core structural knowledge over peripheral knowledge in challenging tasks? Do you have thoughts about that? And why are the more highly clustered stimuli easier to learn? Do we remember them better too?
Thanks - interesting and those beetles are great stimui!
Best
Barb Mellers
Hi Jayme, You concluded that…
Hi Jayme,
You concluded that "category structures with clustering of features are more readily learned than structures that lack clustering, but Sleep may prioritize learning of core structural knowledge over peripheral features in more challenging structures to learn.". I'm curious as to your thoughts about why this happens. Why would feature clusters be more readily learned, and why would sleep preferentially consolidate basic knowledge over peripheral features? It is worth thinking about those questions both from a mechanistic standpoint and from a teleological (i.e. 'why would it be good to do that?') standpoint...
Also, I think Dr. Hunt posed some very good questions are worth wrestling with. Thinking these things through super carefully, in all their glorious messiness, is how super crisp questions and deep understanding emerge. Well done!
Johannes Burge