Where the Science Comes From

This book asks you not to believe it. That goes for the bits that sound like facts too, so here is where they come from and what they actually say.

Most of these are findings about how people in general tend to work, not laws. They hold on average and across lots of people, which is a different thing from holding for you on a Tuesday. The only way to know about you is to try it.

Revising

• Short sessions across a week beat one long cram. This is the spacing effect, and it is one of the most reliably reproduced findings in the study of memory. Look up Cepeda, Pashler and colleagues' 2006 review in Psychological Bulletin.
• Close the book and write what you remember. The testing effect: being asked to retrieve something does more for remembering it than reading it again. Roediger and Karpicke, 2006.
• One tab at a time. Switch costs — moving between tasks has a price in time and accuracy. Rubinstein, Meyer and Evans, 2001. The American Psychological Association has a plain-English summary.
• Fear eats the room you need for learning. Attentional control theory: anxiety pulls attention onto the threat and away from the task. Eysenck, Derakshan, Santos and Calvo, 2007.

Sleep and the body

• Sleep is where today gets filed. Memory consolidation during sleep. Diekelmann and Born's 2010 review in Nature Reviews Neuroscience is the standard starting point.
• Eight to ten hours. That is the published recommendation for 13- to 18-year-olds from the American Academy of Sleep Medicine. The NHS says much the same.

Feelings

• Naming a feeling takes some of the heat out of it. Affect labelling. Lieberman and colleagues, 2007, "Putting feelings into words".
• The long out-breath settles the alarm system. Slow breathing with a longer out-breath shifts the balance of the autonomic nervous system. Zaccaro and colleagues published a systematic review of this in 2018.
• Procrastination is avoidance, not laziness. Sirois and Pychyl, 2013, argue it is mostly about managing how you feel right now rather than managing time.
• Writing unfinished things down helps you stop holding them. This one is the shakiest in the book. It is usually credited to Zeigarnik in 1927, and later attempts to reproduce it have been mixed, which is why the chapter asks you to test it rather than telling you it is true.

The physics

The expansion of the universe and the background radiation left over from the early universe are both standard physics — the radiation was found by Penzias and Wilson in 1965. That a low, heavy object is harder to tip than a tall one is just where its centre of mass sits.

None of it is a claim about how your mind is built. It is a set of pictures, and the note at the front of this book says what to do with pictures.