Everyone makes poor decisions from time to time. Not knowing why they made bad choices, or acted ‘out of character,’ can appear as though humans aren’t in control of their own bodies. Philosophers have argued that such rash decisions can be the result of too much passion, or lack of knowledge. Religion has considered it devil’s work. Science has termed that mysterious agent impulse. By recounting both real-life stories and lab test results, David Lewis offers a glimpse into the triggers that lead to those face-palming moments with Impulse: Why We Do What We Do Without Knowing We Do It.
The author moves deftly from actual events to lab results in order to make his points. Lewis’ opening salvo is a foursome of true stories demonstrating how impulses saved people’s lives, including a personal story of how a whim to visit the cinema helped him avoid a terror bombing overseas. Additional tales explain .how individuals were saved from disaster by listening to a vague ‘gut reaction’ to alter their courses of action.
The human brain’s mode of thinking is split between System R, for slow reflection, and System I, for quick and impulsive. The oft-retold story of Phineas Gage, whose work-related brain trauma brought about life and mood-altering events, leads the reader to an understanding of the areas of the brain that control appropriate versus impulsive behavior. Those same areas of the brain are under-developed in the still growing minds of teenagers, which may explain their susceptibility to impulsive behavior. Further biological explanation is given in the 2D:4D ratio, a method using the length of the pointer finger divided by the length of the ring finger, which predicts risk-taking aversion or acceptance.
Lewis details how 21 senses relay information to the brain, and are influenced by impulse. Beyond the traditional 5 senses, humans have detectors such as thermoception, for heat awareness, and proprioception, for body awareness. Particular attention is paid to the sense of smell, and how it can be manipulated by marketing to lead to impulse purchases, or by individuals trying to attract mates with perfumes and colognes. A later chapter focusing on sight makes interesting note of how cultural differences determine perception, and how gender and beauty are ‘predetermined’ in the brain by recognition of color and symmetry.
The second half of the book focuses on specific impulses. In discussing desire for love and sex, Lewis refers to experiments which show how adrenaline rushes in the company of others can cause people to wrongly attribute the thrill to a partner, or how male preferences for particular female body parts may reveal their personalities. He shows how the body’s primal survival impulse to use sugary, fatty foods as quick bursts of energy is spun by fast food marketers and dessert peddlers in a chapter focusing on eating. “The Buying Impulse” reveals how department stores wield sights and sounds to appeal to human senses. A chapter reviewing mirror neurons demonstrates the human impulse to mimic emotions and actions, and how that leads from everything to reciprocating a smile, to possible extremes like rioting and suicide.
Impulse builds up to a widely accepted scientific notion that ‘free will’ is an illusion, due to evidence that reactions in the brain happen before humans are even aware they are taking a course of action. While this could be seen as incendiary for religious and humanist groups, Lewis’ conclusion takes a philosophic rather than scientific approach. He contests that if science is going to refute free will, society must implement it as an ideal for maintaining order and direction in people’s lives. No doubt religious groups were happy he chose to end the book on that point.