Book review: The 24-hour mind

As a kid I thought that sleep was largely a waste of time. There was so much more we could do if we didn’t have to just lie down like a log for 8 hours or so a night. However, dreams opened up another portal and it felt that dreams redeemed sleep time. I came across The 24-Hour Mind by Rosalind Cartwright on brainpickings and the review looked interesting enough to get the book. I had read Freud’s Interpretation of Dreams a while back and found that somewhat lacking in rigor. This book is far more scientific and for the most part does not try to find meaning in individual dreams, like dreaming of a cat meaning something about your femininity. The book stays clear of the folklore surrounding dreams and that is refreshing.

The major flaw that I see in this book is that most studies are performed on small samples and the effect sizes are not particularly large. In something as complex as human sleep and given that some of the studies described span months to a year, that means that many of the conclusions drawn will likely fade as sample sizes grow larger. A notable absence in the book is the lack of anything to do with lucid dreaming. Also, almost all studies referenced are on people living in the urban West. While sleep is universal, different cultures have different relationships to sleep and it may have been interesting to learn if cultures that have a midday siesta as a part of their routine have differences in sleeping and dream patterns. Or variations between people who live in sunny/equatorial climates and those living in the gloomier climates or in winter in the north.

The book starts off with the early days of sleep research in the 1930s with the investigations by Freud and Jung in abnormal patients and then going on to the more scientific measurements of brainwaves and different sleep states in the 50s. We learn about the different stages of sleep and how sleep disorders played a role in revitalizing dream research. She writes about the differences in various stages of sleep like REM, NREM, and SWS which will show up throughout the book and so are good to remember. The second chapter is on collecting dreams. The best part I liked about it is how she allowed children to draw to express their dreams and I think that that may be effective for adults too. The medium affects the message and we know that something like choice of language changes how people think so it is quite conceivable that verbally describing something or drawing it out would provide differing content. Using just text to write or talk about a dream may mean that we undervalue parts that may be difficult to put into words. Also, not everyone is adept at describing what they are feeling and drawings may bring out certain emotions better.

She talks about her lab’s method of collecting dreams by waking people in the middle of REM sleep and asking what was going on their minds. While I found the method kind of barbaric, I couldn’t think of any better methods myself. Here she goes into the role of emotions in dreams and the difficulties with capturing that. We learn that dreams are longer and more complex toward the end of the sleep and also that REM sleep is intimately connected to learning and new memory formation. This is also corroborated by studies in mice.

“Through the night, from REM to REM, new information is integrated, drawing together more and more remote associations. The dream story line gets stretched into increasingly illogical and bizarre connections.”

Next, the book looks at the connections between sleep deprivation and metabolic and psychological disorders. There are some interesting connections between lack of dreaming during REM sleep in major depression and the effect of antidepressants on REM sleep. In this chapter is one of the more interesting studies described in the book. It focuses on divorce and dreaming and depression. Rosalind looks at some 61 different subjects (low numbers but let’s let that slide) going through divorce. While some of these subjects are depressed, others are not. Following them over a year, she breaks them into 3 groups. First group is those that are not depressed, the second group was depressed in the beginning but not depressed a year later, and the third is depressed both a year later and at the beginning. I think with large enough numbers there should’ve been a fourth group of those who were not depressed in the beginning but depressed a year later but it is missing. Looking at the emotional content of the dreams of these three groups, a conclusion is drawn that those who got over the depression tended to have more positive dreams in the last half of their sleep, while those who did not had more negative dreams. My major issue with the study was that the effect size is low here and I expect it to vanish in a larger study. The low sample size is understandable because getting enough volunteers would be hard and funding would not be easy to come by but on the other hand, it throws many of the conclusions into question. Despite this, the chapter is in interesting and gives the reader something to ponder over and see what one can get from one’s own dreams.

Then we get into sleep related disorders like sleepwalking and other parasomnias. While this topic was particularly fascinating for me, as I used to be a sleepwalker this and the following chapters were among the weakest parts of the book. Firstly, while she acknowledges that sleep walking is quite common in childhood, she focuses on a couple of sleep-related murder cases to a large extent. She takes a personal interest in the Scott Falater case and her credibility suffers as it appears she is too attached to the outcome. There is a bunch of his dreams as an Appendix in the book and I couldn’t figure out what that has to do with the 24-hour mind. Over a span of almost a decade a handful of selected dreams don’t indicate anything one way or the other. There is a lot of speculation on what his mental state was and what happens during the murder and it is a distraction from what the book is about. There is relatively little data and mostly anecdotes and weak ones at that. There is some good parts on what may induce people to sleepwalk and the effect of pharmaceuticals like Ambien on sleepwalking.

The 8th chapter talks about nightmares and other dream related disorders. She looks at people with PTSD and how their sleep patters differ from normal. It is an interesting read. The 9th chapter on Dreaming and the Unconscious talks about the effect of sleep and dreaming on things like problem-solving and creativity. There are references to Freud’s theories of dreaming and how the dreaming may play a role in filtering what is to be remembered or not among the events that happened during the day.

The books ends, appropriately enough, by tying everything together. She asserts that dreams play a role in emotional regulation and updating the self. Given the topic, it is a bit less data driven than the other chapters but it makes some good points. One should read the book if you are interested in sleep in general. Given how much effect sleep (or its lack) have on on waking hours, it is a good read to see what happens when one is persistently sleep deprived and what to watch out for in terms of physical or emotional health.