How We Decide

Human beings often assume that the best decisions come from rational thought, careful analysis, and emotional restraint. For centuries, philosophers from Plato to Kant promoted the idea that emotions corrupt judgment. Modern neuroscience has dismantled this myth. In How We Decide, Jonah Lehrer reveals that emotions and rationality are not opposites—they are partners. The human mind relies on both to navigate complexity, evaluate consequences, and act efficiently. When one system dominates, choices become distorted.

Lehrer uses stories from science, aviation, sports, medicine, finance, and everyday life to illustrate how the brain makes decisions. These examples demonstrate that intuition is an advanced form of knowledge; mistakes help build expertise; and understanding our cognitive biases improves judgment. The book emphasizes that effective decision-making comes from combining instinct, experience, reason, and self-awareness.

The Role of Emotion in Choosing

The belief that emotion interferes with rational thinking collapses when we observe what happens when emotional systems malfunction. One of the most famous cases is that of Elliot, described by neurologist Antonio Damasio. After surgery to remove a tumor near his frontal lobes—regions tied to emotional processing—Elliot retained exceptional intelligence. He could complete logic puzzles and articulate complex ideas, but he could not choose between alternatives. He spent hours debating trivial choices, such as which pen to use or which appointment to schedule first. His life fell apart because he lacked the emotional signals that assign importance and value.

Another example comes from people who suffer damage to the ventromedial prefrontal cortex, often due to injury. These patients can identify risks logically when asked hypothetical questions but make catastrophic decisions in real life—gambling recklessly, entering destructive relationships, or making irresponsible financial choices. Their logic is intact; what’s broken is the emotional feedback that warns them to stop.

Even everyday choices demonstrate how emotion drives decision-making. When someone chooses a dessert at a restaurant, they do not calculate calorie counts and nutritional values—they feel drawn toward something. Without emotional input, every option would appear identical.

This research overturns the stereotype of emotion as chaotic impulse. Instead, emotional signals encode years of past experiences and outcome patterns. They function like compressed data files from previous learning episodes, guiding behavior rapidly and efficiently.

How the Brain Learns Through Prediction and Surprise

Dopamine neurons act as the brain’s internal prediction engine, constantly adjusting expectations based on results. Wolfram Schultz revealed this through experiments with monkeys learning to associate a tone with a drop of fruit juice. Initially, dopamine neurons fired when the monkeys tasted the juice. After repeated trials, the neurons began firing at the sound instead. When the juice exceeded expectations—more than expected—the neurons fired intensely. When no juice appeared, firing dropped below normal, signaling disappointment.

This prediction error mechanism explains how both humans and animals learn from experience.

Example:

• When you try a new restaurant and love it unexpectedly, your dopamine neurons intensify firing. Next time, you feel excitement when thinking about eating there.

• When traffic takes longer than expected, your brain updates expectations and you adjust departure times.

A dramatic real-life example involved Lieutenant Commander Michael Riley on a ...