It’s not clear to me, how can the authors be sure that babies actually learn in their sleep, as opposed to just performing better because they’re not tired?
As a Reinforcement Learning enthusiast, I can't help but see humans learning as they sleep as a "batch". In RL you often delay updating the agent and only update it periodically, just like brains seem to do with sleep.
makes a of of sense too when you spend a of of time learning new things. I've. put time into video games or learning a new programming language and found myself initially struggling. Yet the next day, things I struggled with just make sense without much effort. I've gotten to a point where I view the time reading the material as a passive endeavor, I practice enough to feel like I'm not too stressed out but getting a bit of challenge. The real test comes the next day after sleeping on it.
I think if an advanced adversarial ET ever came into contact with humans they would view this whole "sleep" thing as a huge weakness. Having a period of rest for maintenance, repair, and integration is understandable for an organism -- but why spend a full 3rd of available time on it?
Presumably because it requires a ton of energy, so shutting every other system down is the most effective way? (well, at least when our next energy fix wasn’t so easy to acquire)
I think the reason we sleep so long has a bit to do with our lack of predation. It might be more of an evolutionary accident than a necessity.
Cats are another Apex predator who sleep a lot, but the fact that they do it in naps is probably an evolutionary remnant of when they were not so apex. Primates have been apex for longer (?) and have longer been adapted to sleeping in trees away from predators.
I think you're on to something about energy. I suppose the longer an organism has the luxury of being able to spend in an energy-conservation mode, the more it will do so when evolved in an energy-intensive world. And maintenance/repair/consolidate modes will prefer to converge with these modes as that is a time when it is most safe to perform. So a long time spent sleeping is perhaps emergent in all apex predators who have energy-expensive biologies.
But the substrate / environment of life matters too. Aquatic creatures have shorter sleep cycles because the dangerous environment requires being alert at all times. Apex predators resort to strategies like sharks, who switch half their brain asleep while the other is awake, or whales, who sleep for only up to 30 minutes to maintain breath.
I think a silicone AI or other advanced life-form may evolve to spend similar amounts of time in maintenance mode depending on the energy economy of their environment, but they would do it at shorter timescales that would make competing with it impossible. And the level at which they could function in "sleep" mode would probably rival our awake mode by orders of magnitude.
> I think the reason we sleep so long has a bit to do with our lack of predation. It might be more of an evolutionary accident than a necessity.
I don't think that's backed up by evidence. Elephants, which have very few predators and are really only preyed on when sick, old, or young, sleep only a few hours a day. It's strange because they're highly intelligent and have big, complex brains. Even cats, who sleep a lot everyday, have more predators in the wild, even the big cats. Cats don't sleep long because of lack of predation. They sleep long because they expend huge amounts of energy while awake (i.e., hunting). They require large amounts of energy stored for rabid bursts of expenditure. Sloths sleep a ton, mainly because they're low energy animals.
There are plenty of animals on that list that contradict the conjecture that sleep duration is correlated with predation.
> Aquatic creatures have shorter sleep cycles because the dangerous environment requires being alert at all times. Apex predators resort to strategies like sharks, who switch half their brain asleep while the other is awake, or whales, who sleep for only up to 30 minutes to maintain breath.
That again isn't correct. Dolphins have more predators than sperm whales, yet dolphins sleep much longer per day than sperm whales. Most larger whales don't sleep longer than 30 minutes because they need to be awake and more active to keep their body temperature up. It isn't due to needing to breath as most whales consciously breath just fine while sleeping with the side of the brain that stays awake. Sperm whales don't do this because they can hold their breath for long amounts of time (and sleep vertically, which is quite eery looking). Whales, which includes dolphins, mainly adopted the unihemispherical sleeping primarily because they are conscious breathers.
> I think you're on to something about energy.
I don't think that's much of a revelation. Sleep is all about energy and restoration.
Melatonin - its 4x more potent as an antioxidant than vitamin C and its used to release mesenchymal stem cells, but plastic in our bodies bind to stem cells and prevent them from working. Even plants have higher levels of melatonin if they are picked in the dark. Blue light increases serotonin synthesis, a Japanese study on school kids found those who walked to school had higher levels of serotonin than those who were driven to school, and after going through the food diary, found it was the direct exposure to daylight (bluelight) which increased the serotonin.
Serotonin also increases stem cell (platelets) numbers, SSRI anti depressants suppress stem cell (platelet) numbers.
Interesting study. I wonder if they can find any links with how well babies sleep to the impact it has in adults' sleeping behaviors...whether we carry things from the patterns learned early in life?
