Impulse: Why We Do What We Do Without Knowing Why We Do It
Author: David Lewis


‘We all like to regard ourselves as rational human beings…’ but ‘…our actions are mindless far more often than they are mindful…’ (page xv). This book attributes our mindlessness to impulse, the automatic emotions that influence most our actions. The author says this is the reason we ‘…blurt out indiscretions, rush to judgements, make snap decisions, jump to conclusions, take leaps of faith, and trust gut feelings far more than rational analysis’ (page xv). The book’s strong premise is that our actions are ‘…the product, not of logic and reason, but of habits driven by emotions‘ (page xv).

By Schläsinger - derivative of File:P culture.svg and File:P blank.svg, CC BY-SA 3.0,
By Schläsinger – derivative of File:P culture.svg and File:P blank.svg, CC BY-SA 3.0,

Impulsivity is the product of our intuitive, or what the author labels System I, thinking. This works outside our control, unlike System R thinking which is rational (page 13). These are the same as the System 1 and System 2 thinking styles made popular by the psychologist Daniel Kahneman in his book, Thinking, Fast and Slow. The author argues that System I is our default thinking mode, accounting for most of our cognitive activity. This takes place ‘backstage‘, outside conscious control. The book author states that System R, the conscious reflective thinking mode, is brought in only to give ‘justifying explanations’ for subconsciously predetermined actions. The uncomfortable conclusion is that most of our actions bypass deliberate and reasoned analysis (pages 14 and 26).

gorilla-thinking. patriziasoliani on Flikr.
gorilla-thinking. patriziasoliani on Flikr.

To explore why we are impulsive, and why are some people more impulsive than others, the author traces the development of impulsivity from infancy through childhood. He discusses the factors that determine our impulsivity such as prenatal androgen levels, parenting styles, and socioeconomic status (page 47). The reader is taken through the biological underpinnings of impulsivity ranging from pheromones to dopamine; from personality to physical attributes (pages 67, 112-131). We also learn of the environmental influences on impulsivity such as perfumes, warmth, culture, and the subliminal effects of images and sounds (pages 67-84). The author illustrated his discussions with several interesting observations such as the link between risk-taking and the lengths of the 2nd and 4th fingers, the 2D:4D finger ratio (pages 89-90).

By Coolgirly88 at English Wikipedia - Transferred from en.wikipedia to Commons., Public Domain,
By Coolgirly88 at English Wikipedia – Transferred from en.wikipedia to Commons., Public Domain,

The book views most impulse-driven acts as detrimental, asserting that ‘…impulses lie at the root of most personal and social problems…’ (page xv). This is because many impulses are visceral drives that underlie unhealthy behaviours such as risk-taking (page 185), and they help to sustain medical disorders such as obesity and addiction (page 185). The book argues that impulsivity, by encouraging functional fixedness, limits creativity and obstructs problem-solving (page 21). The author admits that some impulsive actions are ‘functional’ and productive, such as when we learn from others. Nevertheless, his dominant view is that impulsive behaviour has a negative effect on individuals and society.

Flying Free. Mr. Nixter on Flikr.
Flying Free. Mr. Nixter on Flikr.

The book covers a diverse range of subjects such as the fascinating effect of other people’s behaviour on our actions. The author shows the compelling power of this influence, irresistibly pulling us to behave in the same way as others (pages 171-173). This mimicry heuristic is arises from the brain’s mirror neurone system which simulates the actions, intentions, and emotions of others, and is behind destructive mass behaviours such as copycat violence and suicide epidemics (page 156). A similarly interesting discussion is about the significance of the bereitschaftspotential. This is a spike on brain wave recordings that precedes conscious awareness of our intent to act. It was first demonstrated by Benjamin Libet, and the author uses this to support his argument that willpower and self-control are grand illusions (pages 180-201).

Jan Mandyn - The Temptation of Saint Anthony. Gandlaf's gallery on Flikr.
Jan Mandyn – The Temptation of Saint Anthony. Gandlaf’s gallery on Flikr.

The author relates many interesting anecdotes to support his views. An example is the account of Phineas Gage, the railway worker who developed an impulsive personality after surviving an accidental injury to his frontal cortex (pages 27-31). The damage was presumably to his orbitofrontal and anterior cingulate, areas of the brain that regulate emotions and decision-making (page 35). Another anecdote is Walter Mischel‘s marshmallow experiment which demonstrated that children differ in their ability to exert self-control (page 181). This ability has since been shown to determine their success or failure later in adulthood.

By Andy Johnson - Original work by uploader, Domena publiczna,
By Andy Johnson – Original work by uploader, Domena publiczna,

This is an extensively researched book on a very influential human tendency. Knowing how much our actions rely on subconscious influences is enlightening, and helps to explain not only our actions, but those of the patients we care for. I thought the author has an overly negative view of the intuitive cognitive process. Many other works have shown that expert intuitive decision-making is a valuable cognitive tool, and this is stressed for example by Gary Klein in his book Sources of Power, and Gerd Gigerenzer in Gut Feelings. The urge to impulsive behaviour is however very influential, and this book has explored the subject in detail.

Overall assessment

I thoroughly enjoyed this well-written book. It addressed a fundamental issue central to all human activity. Healthcare is facing an epidemic of impulse-driven disorders, and this book helps to put the topic in context. I recommend it to all doctors.

Book details

Publisher, Place, Year: Random House Books, London, 2013
Number of Chapters: 12
Number of Pages: 310
Price: £8.99
Star rating: 4 stars

2 thoughts on “Impulse

  1. You should take a look at the cognitive bias index by John manoojian chart. I have it flipped into one of my own, but it will amaze you at how often our mind is biased when we believe we’re honest in, our own thoughts, decisions, and even opinions.


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