The ACE (Adverse Childhood Experiences) study looked at effects of childhood trauma in 17,000 adults:

• 2/3 of participants reported at least one adverse childhood experience
• 1 in 5 were sexually abused; 1 in 4 beaten or witnessed domestic violence
• More ACEs led to more mental health issues, addiction, health problems and early death. The ACE study showed that childhood trauma is far more common and damaging than previously recognized

Section: 3, Chapter: 8

Author: Bessel van der Kolk

Research on split-brain patients, whose cerebral hemispheres have been surgically disconnected, reveals some startling things about consciousness:

• The two hemispheres display a remarkable degree of functional specialization and independence when separated
• The hemispheres can have separate senses of self, different desires, and even fight against each other for control
• Consciousness itself is divisible by splitting the brain

Subjectively, there is only consciousness and its contents, but the unity of the mind depends on the normal functioning of the corpus callosum connecting the two hemispheres.

Section: 1, Chapter: 2

Author: Sam Harris

In a famous study, male subjects met an attractive female interviewer on either a scary suspension bridge or a stable bridge. The men on the scary bridge were more likely to mistake their physiological arousal (racing heart, sweaty palms, etc) as attraction to the interviewer and call her later for a date. Their conscious minds didn't realize their arousal stemmed from the bridge, not the woman.

Another study found subjects rated erotic pictures as more appealing after vigorous exercise, again mistaking the source of their physiological arousal. Emotions, and the decisions they fuel, arise from many unconscious influences beyond the obvious.

Section: 2, Chapter: 9

Author: Leonard Mlodinow

The Good Judgment Project (GJP), led by Philip Tetlock and Barbara Mellers, recruited thousands of volunteer forecasters to predict global events as part of a tournament sponsored by the research agency IARPA. Questions covered politics, economics, national security and other topics relevant to intelligence analysts.

The GJP used multiple methods to boost forecast accuracy, including training, teaming, and statistical aggregation. But its most striking finding was that a small group of forecasters, the "superforecasters", consistently outperformed others by huge margins.

Across the first 2 years of the tournament, superforecasters beat the "wisdom of the crowd" (the average forecast of all participants) by 60% - a stunning margin. They even outperformed professional intelligence analysts with access to classified data. This suggests that generating excellent prediction accuracy doesn't require subject matter expertise or insider information - just the right cognitive skills and habits.

Section: 1, Chapter: 4

Author: Philip Tetlock

In a study, commuters on Chicago trains were assigned to either talk to a stranger, sit in solitude, or do whatever they normally do. While subjects expected to be least happy talking to strangers, the opposite was true - those who engaged with strangers were most satisfied with their commute. The study suggests that people welcome the opportunity to talk about themselves and have someone take an interest in their lives, even if it's a stranger. But social norms discourage us from these interactions.

Section: 1, Chapter: 3

Author: Kate Murphy

Stanley Milgram's famous experiment showed that most people are connected by about 6 links in a chain. A few key points:

• A very small number of people are connected to everyone else in just a few steps, while the rest of us are linked to the world through those special few.
• In a social epidemic, Connectors spread ideas to a wide range of people, Mavens provide the message itself, and Persuaders convince people to act on that message.
• Paul Revere was a Connector, spreading the word "The British are coming!" His social connections enabled him to tip public opinion and mobilize resistance.

"Six degrees of separation doesn't mean that everyone is linked to everyone else in just six steps. It means that a very small number of people are linked to everyone else in a few steps, and the rest of us are linked to the world through those special few."

Section: 1, Chapter: 2

Author: Malcolm Gladwell

In a famous study, researchers were able to induce false memories in 50% of subjects that as children they had once been lost in a shopping mall, by having relatives recount the fictitious event to them. The "memories" subjects generated felt vivid and real to them. In other studies, subjects came to falsely remember events like being hospitalized overnight, or spilling a punch bowl at a wedding. This shows how readily false memories can be created through suggestion, while feeling indistinguishable from real memories.

Section: 1, Chapter: 3

Author: Leonard Mlodinow

Two landmark prospective studies, by Sroufe and colleagues and by Putnam and Trickett, definitively showed:

• The quality of early caregiving relationships, not temperament or IQ, was the most powerful predictor of mental health outcomes
• Abuse and neglect led to a host of cognitive, emotional, behavioral and health problems that often persisted into adulthood
• Supportive, consistent early caregiving relationships provided a buffer against adversity and promoted resilience

Section: 2, Chapter: 10

Author: Bessel van der Kolk

Stanley Milgram's famous experiments at Yale tested obedience to authority to an unsettling degree:

• "Teachers" were instructed to give increasingly severe electric shocks to a "learner"
• The shocks weren't real, but the teachers thought they were
• Over 60% of subjects fully obeyed the experimenter and continued to the highest voltage, even with the learner screaming in agony
• Subjects were everyday people deeply distressed by their actions, but they still obeyed
• Shows the immense power of authority - and the human capacity for cruelty under its direction

Section: 1, Chapter: 6

Author: Robert Cialdini

The Ultimatum Game is a famous experiment in behavioral economics that tests people's perceptions of fairness.

Player A is given a sum of money (the "pie") and told they must offer some share of it to Player B

• If Player B accepts the offer, both players get the agreed amounts
• If Player B rejects, neither player gets anything

Even though Player B should rationally accept any positive offer, since something is better than nothing, in practice offers perceived as unfairly low (usually below 20% of the total) are often rejected.

With skin in the game, people are even more willing to sacrifice to enforce fairness. The Ultimatum Game reveals a deep human aversion to getting shortchanged.

Section: 4, Chapter: 15

Author: Richard Thaler

MIT's Human Dynamics Lab, led by Professor Alex Pentland, used sociometric badges to measure the behavioral signals exchanged in successful groups. They found that high-performing groups consistently displayed a set of subtle cues that generate feelings of belonging and safety:

• Close physical proximity (often in circles)
• Profuse amounts of eye contact
• Lots of short, energetic exchanges (no long speeches)
• High levels of mixing; everyone talks to everyone
• Few interruptions
• Intensive, active listening
• Humor, laughter

Pentland found that belonging cues were the single greatest predictor of group performance, more important than all the individual skills and intelligence of the group's members. These cues trigger the release of oxytocin and activate neural pathways of trust and cooperation, enabling the group to sync their behaviors and act as one.

Section: 1, Chapter: 1

Author: Daniel Coyle

Experiments by psychologist Thomas Zentall show that pigeons will consistently choose a "gambling" game that provides less food overall, mimicking the human slots players Si Redd observed.

When pigeons can choose between:

1. A "sure thing" game providing a medium food reward 50% of the time, or
2. A "gambling" game with a larger food reward only 20% of the time

An overwhelming 96.9% of pigeons prefer the "gambling" game, even though it provides less food! The larger unpredictable reward taps into an instinctual attraction to variable payouts. This behavior is seen across many animals.

Section: 1, Chapter: 2

Author: Michael Easter

In animal studies, total sleep deprivation kills rats and flies faster than total food deprivation. Key findings include:

• Rats died after 15 days of total sleep deprivation, on average
• This was about the same time it took for rats to die from total food deprivation
• Rats lost their lives almost as quickly from selective REM sleep deprivation as from total sleep deprivation
• Prior to death, the rats developed skin lesions, weight loss, hypothermia and sepsis (bloodstream infection)

These animal experiments prove that sleep is a life-sustaining biological necessity, not just a "nice to have." Sleep is arguably more essential for survival than food in the short-term. Sleep deprivation essentially causes the body to "self-destruct" through multiple organ failure if pushed to the extreme.

Section: 4, Chapter: 12

Author: Matthew Walker

Lesson 1: Do not obey in advance: Don't voluntarily conform to a new authoritarian system before it fully takes hold.

The famous Milgram experiment at Yale in 1961 showed how quickly people will follow the commands of an authority figure, even if it means harming others. Subjects were told to administer shocks to unseen participants, and most continued to do so even when the person seemed to be in agony or dying, simply because the experimenter told them to continue. This reveals how people adapt to new authority, a key ingredient in the transition to tyranny.

Section: 1, Chapter: 1

Author: Timothy Snyder