Deep Dive: Thinking, Fast and Slow

This is one of my favorite books and a book I recommend to almost anyone. It covers what I find to be a set of important 'behaviors' we all experience in different ways. To me, it made two very compelling arguments; first, the way we think we 'think' is probably not very close to the way we actually think; secondly, what we think about and how we make decisions is impacted by myriad 'small' things around us. Apart from what I find to be compelling arguments, the book is full of experiments, studies, anecdotes, and information which range from midly interesting to totally fascinating.

In the years since I first read this book (and, later on in this post the book 'Pre-suasion') I have wanted to put together a brief 'cheatsheet' of the key takeaways of the many studies and try to bring the insights more practically into my life. This post is an attempt at extracting some of the key ideas and I intend to update periodically with (a) other books which I find have similar impact and which focus on similar topics and (b) any behaviors or notable experiences I have trying to incorporate some of these insights into my life.

If this sounds even mildly intersting to you, I hope you'll at least skim some of the experiments and takeaways as I'm sure anyone can find at least one which surprises them!

Part 1: The Two Systems

Chapter 1: The Characters of the Story

The Experiment: The Müller-Lyer Illusion

  • Citation: Müller-Lyer, F. C. (1889). Optische Urteilstäuschungen
  • The Setup: Subjects are shown two lines of identical length. One has fins pointing inward (creating an arrow shape), the other has fins pointing outward.
  • The Result: Even after measuring the lines and knowing (System 2) they are equal, the subject's eyes (System 1) still see one line as longer than the other.
  • The Mechanism: Cognitive Illusion. System 1 operates automatically and cannot be "turned off" simply by knowing the truth. System 2 must actively correct System 1's error, which requires effort.

Chapter 2: Attention and Effort

The Experiment: The "Add-1" and "Add-3" Pupil Studies

  • Citation: Kahneman, D., & Beatty, J. (1966). Pupil diameter and load on memory
  • The Setup: Subjects hear a string of 4 digits (e.g., 5-2-9-4) and must repeat them back while adding 1 (or 3) to each digit (e.g., 6-3-0-5) to the beat of a metronome.
  • The Result: As task difficulty increased, subjects' pupils dilated significantly (up to 50%). When the task became impossible (overload), pupils stopped dilating and subjects effectively went blind to other stimuli.
  • The Mechanism: Mental Economy. System 2 has limited bandwidth. Physiological markers (pupils) prove that thinking is a biological cost. When System 2 is maxed out, we become "blind" to the outside world to protect the primary task.

Chapter 3: The Lazy Controller

The Experiment: Radishes vs. Chocolate Cookies

  • Citation: Baumeister, R., et al. (1998). Ego depletion: Is the active self a limited resource?
  • The Setup: Hungry participants enter a room smelling of cookies. Group A is allowed to eat cookies. Group B is forced to eat only radishes. Both groups are then given an impossible geometry puzzle to solve.
  • The Result: The "Radish" group gave up on the puzzle in 8 minutes. The "Cookie" group lasted roughly 19 minutes (same as a control group).
  • The Mechanism: Ego Depletion. Self-control is a finite resource (consumes glucose). Resisting the cookies "spent" the mental energy required to solve the puzzle. System 2 gets tired.

Chapter 4: The Associative Machine

The Experiment: The Florida Effect

  • Citation: Bargh, J., Chen, M., & Burrows, L. (1996). Automaticity of social behavior
  • The Setup: Young students unscrambled sentences. Group A had neutral words. Group B had words associated with the elderly (Florida, bald, gray, wrinkle).
  • The Result: When leaving the experiment, Group B walked significantly slower down the hallway than Group A, without realizing why.
  • The Mechanism: Ideomotor Effect. Priming a concept (Old Age) triggers a physical behavior (Walking Slow) via associative coherence. The brain seeks to align the body with the current mental state.

Chapter 5: Cognitive Ease

The Experiment: The CRT in Blurry Font

  • Citation: Alter, A., Oppenheimer, D., et al. (2007). Overcoming intuition
  • The Setup: Subjects took the Cognitive Reflection Test (logic puzzles). Half saw it in a clear font; half saw it in a faint, hard-to-read gray font.
  • The Result: 90% of the "Clear Font" group made intuitive mistakes. Only 35% of the "Blurry Font" group made mistakes.
  • The Mechanism: Cognitive Disfluency. When things are difficult to read, "Cognitive Ease" is broken. This alarm signal wakes up System 2 to pay attention, resulting in higher accuracy.

Part 2: Heuristics and Biases

Chapter 10: The Law of Small Numbers

The Experiment: Kidney Cancer Rates

  • Citation: Wainer, H. (2007). The Most Dangerous Equation
  • The Setup: A study shows that counties with the lowest rates of kidney cancer are rural and Republican. A separate study shows counties with the highest rates are also rural and Republican.
  • The Result: People invent causal stories for both (e.g., "Clean air prevents cancer" vs. "Pesticides cause cancer").
  • The Mechanism: Sample Size Neglect. Rural counties have small populations. Small samples yield extreme results (high or low) purely by chance (noise). There is no causal story, only statistical artifact.

Chapter 11: Anchors

The Experiment: The Wheel of Fortune

  • Citation: Tversky, A., & Kahneman, D. (1974). Judgment under Uncertainty: Heuristics and Biases
  • The Setup: A rigged wheel stops at 10 or 65. Subjects are asked: "Is the percentage of African nations in the UN higher or lower than this number?" Then: "What is your guess?"
  • The Result: Those who saw 10 guessed ~25%. Those who saw 65 guessed ~45%.
  • The Mechanism: Anchoring Effect. The initial number (even if known to be random) acts as a starting point. System 2 adjusts away from the anchor but stops too early (laziness), biasing the final estimate toward the random number.

Chapter 13: Availability, Emotion, and Risk

The Experiment: Estimates of Causes of Death

  • Citation: Slovic, P., Fischhoff, B., & Lichtenstein, S. (1982). Facts and Fears
  • The Setup: Subjects estimated the frequency of death from various causes (e.g., Tornadoes vs. Asthma; Accidents vs. Strokes).
  • The Result: Accidents were judged to cause 80% as many deaths as strokes (Reality: Strokes cause ~2x more). Tornadoes were judged as more frequent than asthma (Reality: Asthma causes 20x more).
  • The Mechanism: Availability Heuristic. We judge frequency by how easily examples come to mind. Dramatic, media-covered events (tornadoes, crashes) are highly "available" in memory, distorting our risk perception.

Chapter 15: Linda: Less is More

The Experiment: The Linda Problem

  • Citation: Tversky, A., & Kahneman, D. (1983). Extensional versus intuitive reasoning
  • The Setup: Linda is described as a social activist. Subjects choose which is more probable: (A) Linda is a bank teller. (B) Linda is a bank teller and active in the feminist movement.
  • The Result: 85% of undergraduates (and even medical students) chose B.
  • The Mechanism: Conjunction Fallacy. Logically, a subset (Teller + Feminist) cannot be more probable than the whole set (Teller). However, B is more representative of Linda's description. System 1 favors "Coherence" (a good story) over "Probability" (logic).

Part 4: Choices (Prospect Theory)

Chapter 26: Prospect Theory

The Experiment: Loss Aversion Coefficient

  • Citation: Tversky, A., & Kahneman, D. (1992). Advances in prospect theory
  • The Setup: You are offered a coin toss. Tails: You lose $100. Heads: You win $X. What must X be for you to accept the bet?
  • The Result: The average person requires X to be roughly $200.
  • The Mechanism: Loss Aversion. The psychological intensity of losing $100 is twice as powerful as the pleasure of gaining $100. The "value function" is steeper for losses than gains.

Chapter 27: The Endowment Effect

The Experiment: The Mug Study

Chapter 34: Frames and Reality

The Experiment: The Asian Disease Problem

  • Citation: Tversky, A., & Kahneman, D. (1981). The framing of decisions
  • The Setup: A disease threatens 600 people.
    • Positive Frame: (A) Save 200 lives. (B) 33% chance to save 600.
    • Negative Frame: (C) 400 will die. (D) 33% chance no one dies.
  • The Result: In Positive Frame, 72% choose A (Risk Averse). In Negative Frame, 78% choose D (Risk Seeking).
  • The Mechanism: Framing Effect. The logical outcomes are identical. However, when the outcome is "Saving Lives" (Gain), we prefer certainty. When the outcome is "People Dying" (Loss), we gamble to avoid the loss.

Part 5: Two Selves

Chapter 35: Two Selves

The Experiment: The Cold Pressor (Colonoscopy Analog)

  • Citation: Kahneman, D., et al. (1993). When more pain is preferred to less
  • The Setup:
    • Trial A: Hand in 14°C water for 60 seconds.
    • Trial B: Hand in 14°C water for 60 seconds, followed by 30 seconds at 15°C (slightly warmer, but still painful).
  • The Result: When asked which trial they would repeat, nearly 70% chose Trial B.
  • The Mechanism: Peak-End Rule / Duration Neglect. The "Remembering Self" does not sum up total pain. It averages the Peak pain and the End pain. Trial B had a better "End," so it is remembered as less painful, despite being longer.

Deep Dive: Pre-Suasion

A similarly good book

Part 1: The Frontloading of Attention

Chapter 2: Privileged Moments

The Experiment: "Are You a Helpful Person?"

  • Citation: Bolkan, S., & Andersen, P. (2009). The impact of self-prophecy on compliance
  • The Setup: Researchers stopped strangers.
    • Control: "Will you complete this survey?"
    • Pre-Suasion: "Do you consider yourself a helpful person?" (Wait for "Yes") -> "Will you complete this survey?"
  • The Result: Compliance jumped from 29% (Control) to 77.3% (Pre-Suasion).
  • The Mechanism: Commitment and Consistency. By answering "Yes" to the first question, the subject internally identifies as "Helpful." When the request follows, they must comply to remain consistent with that new identity.

Chapter 3: The Importance of Attention

The Experiment: Sofas: Clouds vs. Pennies

  • Citation: Mandel, N., & Johnson, E. J. (2002). When web pages influence choice
  • The Setup: An online furniture store A/B tested two background images for their landing page: (A) Fluffy Clouds, (B) Pennies.
  • The Result:
    • Clouds: Customers spent more time looking at "Comfort" ratings and bought softer, more expensive furniture.
    • Pennies: Customers spent more time looking at "Price" and bought cheaper furniture.
  • The Mechanism: Directed Attention. The background image primed a specific goal (Clouds = Comfort; Coins = Economy). This biased the "search" phase of decision-making before the customer even read a product description.

Chapter 4: What’s Focal Is Causal

The Experiment: The Interrogation Camera Angle

  • Citation: Lassiter, G. D., et al. (2001). Videotaped confessions: Is guilt in the eye of the camera?
  • The Setup: Mock jurors watched a video of a police interrogation.
    • Angle A: Focused on the Suspect.
    • Angle B: Focused on the Detective.
  • The Result: Those who watched Angle A (Suspect) rated the confession as voluntary and the suspect as guilty. Those who watched Angle B (Detective) rated the confession as coerced.
  • The Mechanism: Visual Salience. We intuitively assign causal power to whatever we are looking at. If the suspect is the visual focus, we perceive them as the "driver" of the action.

Chapter 5: Commanders of Attention (Attractors)

The Experiment: Valentine St. vs. Martin St.

  • Citation: Guéguen, N. (2012). Mating cues and helping behavior
  • The Setup: A young woman asked men for help (to retrieve a stolen cell phone) in two different locations:
    • Location A: In front of a florist (or asking for Valentine St).
    • Location B: In front of a bakery (or asking for Martin St).
  • The Result: Men were significantly more willing to help in the Florist/Valentine condition.
  • The Mechanism: Sexual/Romance Priming. The environmental cues (Flowers/Valentine) activated the "Courtship" sub-routine in the male brain, which includes "be helpful and heroic" as a strategy.

Chapter 7: The Primacy of Associations

The Experiment: German vs. French Wine

  • Citation: North, A. C., Hargreaves, D. J., & McKendrick, J. (1997). The influence of in-store music on wine selections
  • The Setup: A supermarket played either accordion music (French) or Oompah music (German) near the wine section.
  • The Result:
    • French Music: French wine outsold German 5-to-1.
    • German Music: German wine outsold French 2-to-1.
    • Note: 86% of shoppers denied the music affected them.
  • The Mechanism: Associative Coherence. The music pre-suaded the brain by activating a network of associations (France = Sophistication/Wine). This made French wine feel like the "right" choice for the moment, bypassing conscious logic.

Chapter 9: The Mechanics of Pre-Suasion

The Experiment: The Warm Coffee Study

  • Citation: Williams, L. E., & Bargh, J. A. (2008). Experiencing physical warmth promotes interpersonal warmth
  • The Setup: An experimenter handed a subject a cup of coffee to hold briefly in the elevator (ostensibly to tie their shoe).
    • Condition A: Hot Coffee.
    • Condition B: Iced Coffee.
    • Later, the subject read a description of a stranger.
  • The Result: Hot Coffee holders rated the stranger as having a "warmer" personality (generous, caring). Iced Coffee holders rated them as colder/more distant.
  • The Mechanism: Embodied Cognition. The brain uses physical metaphors to understand abstract concepts. Physical warmth activates the neural pathways for social warmth.

Part 3: Unity (The 7th Principle)

Chapter 11: Unity (Being Together)

The Experiment: The Parents' Survey

  • Citation: Cialdini, R. (2016). Pre-Suasion (Original classroom data).
  • The Setup: Students were assigned to get a survey filled out by their parents (a high-effort task with typically low compliance). Cialdini offered 1 extra credit point (negligible value) if they succeeded.
  • The Result: Compliance rose to 97%.
  • The Mechanism: Kinship Unity. The incentive was irrelevant. The compliance came because the task invoked "Helping the Family." We help those who share our genes (or shared identity) vastly more than strangers.

Chapter 12: Unity (Acting Together)

The Experiment: Synchronized Tapping

  • Citation: Wiltermuth, S. S., & Heath, C. (2009). Synchrony and cooperation
  • The Setup: Subjects listened to music and tapped cups.
    • Group A: Tapped in sync with the experimenter.
    • Group B: Tapped out of sync.
  • The Result: Later, Group A was 3x more likely to help the experimenter with a burdensome task.
  • The Mechanism: Synchrony. Acting together physically (marching, dancing, chanting) blurs the self-other boundary. The brain perceives "We are one," leading to self-sacrificial behavior.

Chapter 12: Co-Creation

The Experiment: Advice vs. Opinions

  • Citation: Liljenquist, K. A. (2010). Resolving the impression management dilemma (Dissertation/Work cited by Cialdini).
  • The Setup: Pitching a business plan to a superior.
    • Approach A: "Can I get your opinion?"
    • Approach B: "Can I get your advice?"
  • The Result: Approach B resulted in significantly higher buy-in and support for the plan.
  • The Mechanism: Co-Creation Unity. Asking for an opinion puts the person in the role of a judge (separation). Asking for advice puts them in the role of a partner (unity). People support what they helped create.