Psychology: Sleep and Intelligence (Learning, Memory)

hello and welcome to the world of psychology this is my very first episode in English maybe you've already became aware of my accent I'm in fact from Germany I'm a German psychology student a German podcaster so this is my first episode in English but it's not my first podcast episode in fact I've produced quite a lot of episodes in German up to now but I realized that there are many people are interested in psychology and especially in psychological research and this is what the podcast is going to be about it's about the recent research in psychology so we are not going to talk about Pavlov's operant conditioning or Maslow's pyramid of needs we are going to look at studies that have been published in the last years or maybe this year so this is what I'm really a little bit nerdy about I really enjoy reading all this stuff and I enjoy sharing this stuff but enough bla bla for the moment I think during the episodes there will be plenty of time to get to know each other so let's get it started I'd like to begin with a quote from the famous inventor of the light bulb Thomas Edison somehow he is responsible for the fact that people today sleep much less than two hundred hundred or even seventy years ago for example in 1942 people slept about seven point six hours in 2001 people slept that this is the result of a survey of the Gallup Institute people slept only six point seven hours so people sleep almost one hour less then about 70 years ago and one reason one main reason for this development of course is the invention of the light bulb so let's take a look at the quote when I went through Switzerland in a motor car so that I could visit little towns and villages I noted the effect of artificial lights on the inhabitants where water power and electric lights had been developed everyone seemed normally intelligent where these appliances did not exist and the natives went to bed with the chickens staying there until daylight they were far less intelligent so obviously Edison had the opinion that people having no electric light were as dumped as the chicken they went to bed with well I suppose he meant that they went to bed at the same time and not you know this indeed is a hypothesis we have to take serious because maybe people having electric lights can stay awake longer and they can still their brains by having cognitive stimulating discussions or maybe they have time to read interest in books so maybe this is for real and in fact on first sight they even is some scientific evidence for this because at the same time when people began to sleep less and less people seemed to become more and more intelligent indeed people have become more and more intelligent in the last decades maybe you've heard of this effect is called the Flynn effect observed by the New Zealand scientist James Flynn and he observed that in the last decades people became better in solving intelligence tasks so there really is a correlation between sleeping less and people getting more and more smart but it's only a correlation and we have to be very careful with correlations because they don't tell us anything about the causal link we don't know if sleeping less is really the reason for people getting more intelligent in fact there are many reasons to believe that other factors are more important for example education people are much better educated than hundred years ago they go to school for a much longer time parents are more interested in a good education for their children and there are so much more information to learn for students today then maybe fifty or hundred years ago so this might be a reason another reason may be more healthy diets people get much better food than ten hundred or fifty years ago you can get almost every fruit and vegetable even in winter at minus 20 degrees so this might be another reason for the Flynn effect so even though there's a correlation between sleeping less and intelligence shorter sleep might have no influence on intelligence at all they even might have a negative influence which is being compensated by other factors like better education or healthier diets and in order to really investigate the influence of sleep and to find out whether Edison was right or wrong we need experiments because in comparison to correlations experiments are able to tell us about the causal links and there are two studies I want to report to you of course there are much more other studies but from a methodological point of view I think these studies are really nicely designed and the first study is from fund Dolan and colleagues it's been published in 2003 and in this study people were forced to sleep either eight hours well this is not that hard six hours this is for some people this is already heavy and for four hours this is quite heavy as they had to sleep these amounts of time for 14 days and if you take a look at the results it's obvious that Edison was wrong because if we sleep less and the less we sleep our cognitive ability is declined for example our working memory gets worse in the second study which was published by Lo and colleagues and I think the most famous sleep scientists here is dirk von dyke in this study people again were forced to sleep for only six hours and as I mentioned this is quite hard for some people a few people get along with this time but for most people this is clearly two hours to less so they again observed some decline in tensional tasks for example participants observed countdown on the screen like 8 7 6 5 and so on and when the countdown reached 0 they had to push a button so this is really very easy but the really interesting result about this study was in such tasks in easy tasks people became clearly much worse than in more complicated more heavy tasks like working memory tasks which was a visual and back task imagine you're sitting in front of the screen and you have shown a sequence of letters for example a b d a and in the condition 3 back you have to push the button when the letter you see is the same as 3 steps before so in the case of a p d a you have to push the button because a was the same letter as three steps before so you have to remember every letter as three steps later it could appear again so this is a more heavy working memory task and it seems like in these tasks the results of sleep deprivation are not that big so if you should have an exam the other day and you are and you've slept really bad you don't have to be that concerned about your abilities because in a complex situation like an oral exam for example your cognitive abilities will not be that much influenced but and this is very important for drivers in simple attention tasks like the task with the countdown and we can compare this to driving because when we are driving it's not a big cognitive challenge we just have to be awake and if we got to less sleep like we were sleeping only six hours when we are when we usually sleep about eight hours our ability to drive may be a little impaired so it's not surprising that at least in Germany about one fourth of all fatal car accidents are caused by the dangerous microsleep and in fact in Australia or the u.s. that the number is even higher because there are so many long and monotonal highways that cause us to be even more sleepy so if you got to less sleep you have to be very careful because when you fall asleep for only one second at the speed of 100 km/h you drive 28 meters and this is a quite dangerous distance to drive with closed eyes so if sleep loss impairs cognitive abilities this should really have consequences for education parents should set strict rules for their children when to stop watching TV when to stop playing video games I mean today's video games are programmed in a way which makes it really hard to stop playing and those games can really keep you awake all night long with the results of being very exhausted during the next day's lessons and in fact some sleep scientists think that some cases of ADHD are in fact cases of chronic sleep deprivation often caused by pupils playing video games till 2 o'clock or three o'clock a.m. another way of giving pupils the chance to get sufficient sleep might be delaying school start times there are not many studies that have observed the results of a later school start and there's still some controversy about it but there's one well-done study by Carol McKeon and West that has been published recently and in this study they observed the school achievements of the students of the US Air Force Academy this was a really great sample to observe the effects of different starting times because as there are too many students not all students can be put in one course so students are put in an earlier course or in a later course at random and when Carol McKeon and West analyzed the grades of the students they observed that those students who had to attend an earlier course did not only sleep less they also had worse grades and not only in this early morning course but also in courses that were later that day so it seemed like having to attend an early class means that you get less sleep and this seems to have consequences for your achievement in this early morning class and as you have a sleep deficit this seems to influence your performance in the following classes so there's indeed some evidence that students might profit from later school starts the sites the studies on sleep deprivation there is another very interesting line of research that shows the importance of sleep for successful learning and it's all about memory consolidation in fact there's more and more evidence that during sleep there seems to be a replay diet prefer to call it a remix because we don't exactly redream what we've experienced during the day but we combined the experience of the day or or of the last few days with older memories and this association process might be one reason why our dreams are sometimes really strange as I mentioned there are more and more studies that supports the idea of replay one of the former studies is the study from Robert Stickgold who had participants play Tetris for seven hours over a period of three days and in the nights he he woke them up again and again and asked what they had dreamt about if you want to know what you're dreaming at night you just have to ask somebody to wake you up the end the probability that you remember what you've dreamt is quite high so in this study about 75% of the participants reported to have dreamt about falling stones they were not always exactly dreaming about tea trees but they were dreaming of stones falling down which were quite similar to the game situation so this was one of the first very interesting studies a second study which was conducted by Yee and Wilson in the year 2007 became famous because in this study rats were put in a labyrinth and while walking their way they became rewarded if they chose a special way this is not very spectacular but while they were walking in the labyrinth they had electrodes put on their head and interestingly almost the same parts of the brain almost same neurons were firing when they were walking in the labyrinth and afterwards when they were sleeping so again this is evidence for the so-called replay hypothesis if there's a replay why is there replay or a remix well you just have to put one and one together one of the oldest laws in learning psychology is the law of repetition so the more often you do something the better you get and if the brain is replaying what it experienced the day before it should get better it should learn easier and in fact there are there are more and more studies that show that this is really the case for example in one study which was published by Tucker and colleagues in 2011 in the famous journal plus one for example in this study they had 152 participants Harvard undergraduates and what they were really interested in in this study was to examine whether there's a difference according to memory consolidation when you tell participants you'll get rewarded you'll get money if you have better learning results what did they have to learn well they just had to learn visual part associates which means they were presented pictures of faces black-and-white pictures and in combination with every picture they had to learn one object which was for example a protractor and they wanted to observe whether the sleep dependent memory consolidation the sleep dependent learning of these paired associate visual paired associates could be influenced by telling people well you will get rewarded so in a way it's like telling the brain hey I know you are processing information at night so what if I give you a little bit money are you going to the information even better well to make a long story short the brain couldn't be corrupted but what they found and has been found in many others studies right now was that the group that learned at 9 p.m. in the evening then went to bears so had a good sleep and probably there's been a replay and was tested at 9 a.m. was significantly better than the group that had learned at 9 a.m. and was tested again at 9 p.m. so this group didn't have asleep in between the learning phase and the test so this memory consolidation might not be influenced by reward but there obviously is a memory consolidation now you might be wondering how can I use it if sleep is important for learning when is the best time to learn is it better to learn at 3:00 p.m. or maybe it's better to learn at 9:00 p.m. before we go to bed so the last study we're going to talk about was exactly about this question the title of the study is the timing of learning before night sleep differentially effects declarative and procedural long term memory consolidation in adolescence it's been published by johannes Holtz and colleagues in July 2012 in this study 50 female participants aged sixteen to seventeen years were divided in two groups one group learned at 3:00 p.m. and the other group learned at 9:00 p.m. the participants of both groups had to learn two tasks one was about work pass what like for example the word pair river and boat so this was a little bit like learning vocabulary and when they were tested again and they were just shown the word River and they had to put in boat so this was not very complicated the other task was a motor task which was in fact just a photo task for your fingers they had to put in a sequence of numbers as fast as possible for example they had to tip in the numbers 4 2 3 1 4 and this as fast and as correct as possible the results for this finger tapping task were like they had expected the group that had learned in the evening at 9 p.m. and was retested at 9:00 a.m. after a night of sleep they performed significantly better and they even performed significantly better seven days later the results for the word pair test were more surprising because the group that had learned at 3 p.m. and was retested the same day at 9 p.m. achieved better results so maybe but we have to be very careful here even the scientists are very careful with their conclusion because the results for the word pair test were not that statistically robust but maybe it's better to learn vocabulary in the afternoon and there is some evidence that learning motor tasks I mean this finger tapping can be compared to the finger movements you need when you play violin or if you play piano so learning these motor tasks may be better right before you go to sleep this has been the first episode I hope you enjoyed it