The Optimism Bias

Why do you often assume things will work out fine—even when they might not? In The Optimism Bias, cognitive neuroscientist Tali Sharot reveals that this widespread tendency to expect the best is not just wishful thinking. It is a biologically ingrained feature of the human brain, one that shapes memory, emotion, and behavior. Sharot argues that people everywhere—from pilots to politicians—carry a powerful bias that colors their perception of reality through rose-tinted lenses.

Optimism Is Hardwired, Not Learned

Sharot begins with a striking observation: even when people face uncertain futures, they imagine scenes filled with achievement and joy. She discovered this effect almost by accident while studying memory formation after 9/11. Participants asked to picture routine future events—like getting a haircut—couldn’t resist transforming them into idealized, celebratory versions. This spontaneous positivity occurs whether someone is young or old, wealthy or poor. Indeed, studies show that optimism persists across cultures and ages, implying that it is a deeply rooted cognitive bias rather than a learned habit or cultural artifact.

Why It Matters: Evolution and Survival

Sharot contends that optimism evolved as an adaptive mechanism. The human capacity to imagine future scenarios—what psychologists call prospection—likely developed alongside an optimistic lens. Without it, our ancestors might never have ventured beyond safe territory or endured hardship in pursuit of long-term goals. This evolutionary link explains why optimism contributes not only to personal motivation but also to mental and physical health. It reduces stress, increases resilience, and may even lengthen lifespan. However, as Sharot warns, this same bias can blind us to risk, leading to flawed decisions in everything from marriage to military invasions.

Illusions of the Mind

Optimism is one of several cognitive illusions Sharot explores alongside perceptual examples—from visual tricks like the Checker Shadow illusion to navigational errors that caused real disasters, such as pilots suffering vertigo and believing they were flying level when fatally spinning downward. These distortions reveal a central theme: our brains construct reality, not merely record it. Just as eyes deceive us under certain conditions, our minds distort probabilities, rewards, and memories to favor hopeful interpretations. The optimism bias is thus not a form of naivety—it is an evolved way of seeing the world that guides action and sustains hope.

The Self-Fulfilling Prophecy

At its heart, Sharot’s message is paradoxical: irrational optimism can produce rational success. Believing a better future awaits inspires the behaviors that can make it real. Her examples—from basketball coach Pat Riley’s championship prediction to heart patients who lived longer because they expected recovery—illustrate how expectations reshape motivation and even biology. The human mind, she argues, is organized to try to transform predictions into reality. By anticipating good outcomes, we activate neurobiological circuits that align behavior with belief.

When Optimism Fails

The optimism bias is not universally beneficial. Sharot devotes part of her study to depression, pessimism, and genetic factors that disrupt the brain’s positive filter. When optimism circuits falter—particularly in the communication between the anterior cingulate cortex and the amygdala—people lose the ability to imagine pleasant futures. This neurological breakdown, she shows, underlies clinical depression. Similarly, excessive optimism, when unchecked, can lead to disasters like the financial crash of 2008 or Stalin’s refusal to believe his intelligence agents. The challenge is not to suppress optimism but to become aware of it, managing its power rather than denying it entirely.

The Mind’s Architecture of Hope

Throughout The Optimism Bias, Sharot walks the reader through neuroscience experiments showing that optimism is mediated by specific brain circuits, especially those involving dopamine and the frontal cortex. When people imagine the future, these regions light up as they filter information, embracing the positive and ignoring the negative. This creates a natural asymmetry in learning—one that helps maintain well-being at the expense of objectivity. Yet Sharot concludes on an encouraging note: understanding this bias lets us harness it consciously. Like pilots learning to rely on instruments rather than inner orientation, humans can balance constructive hope with informed realism.

Ultimately, Sharot’s book invites you to recognize optimism as both your greatest illusion and your greatest strength. By unpacking the neuroscience behind why the glass often looks half full, she shows that this bias—far from being foolish—is one of humanity’s most powerful engines for progress, creativity, and survival.

Sharot introduces the concept of cognitive illusions through striking analogies to visual perception. Just as a checkerboard can fool the eye into seeing contrasting shades that don’t exist, your brain also distorts abstract data—confidence, probability, and personal ability—to create comfort and coherence. These illusions arise from the brain’s evolutionary shortcuts: systems calibrated for simplifying chaos rather than recording perfect reality.

Visual and Spatial Illusions

Sharot opens Chapter 1 with the tragic crash of Flash Airlines Flight 604, in which the pilot fell prey to spatial disorientation. Believing his aircraft was level, he unwittingly guided it into a catastrophic spin. The brain’s navigational system evolved for terrestrial life, not high-speed flight, so sensory cues become misleading in darkness or turbulence. Pilots, like thinkers, must learn to trust data over intuition—a theme Sharot extends to optimism itself.

Cognitive Illusions in Everyday Life

Beyond the cockpit, similar misreadings govern our daily judgments. The “superiority illusion” convinces most people that they are above average at driving, leadership, and friendliness—a mathematical impossibility. We also suffer from the “bias blind spot,” believing others are susceptible to biases while we are rational observers. Justice Antonin Scalia illustrates this illusion when he insisted his friendship with Dick Cheney didn’t influence a Supreme Court ruling, blind to his own partiality. These biases help maintain self-esteem but distort perception of fairness.

Choice Blindness and Introspection Illusion

Sharot recounts fascinating experiments by Swedish researchers Petter Johansson and Lars Hall, who showed participants two photographs and asked which face they found more attractive. After switching the photos without notice, most participants failed to detect the swap and rationalized their ‘choice’ with fabricated reasons. This phenomenon, known as choice blindness, reveals how people invent self-narratives for decisions they didn’t make. Sharot calls this the introspection illusion—the mistaken belief that we can access our true motives when we’re mostly guessing.

The Role of Illusions in Adaptation

Why do our brains cling to these false views? Because illusions serve survival. Spatial biases once kept primitive humans upright; superiority biases keep modern humans ambitious. Sharot argues that illusions are not defects but design features—mental lenses that enhance confidence and spur progress. Like vertigo for pilots, optimism can lead to disaster if unchecked, but it also keeps humanity flying toward possibility.

In short, your sense of certainty is more fragile than it feels, yet this fragility keeps you sane and striving. By learning to recognize illusions without dismantling them, you can maintain balance between confidence and caution—a pilot relying on instruments rather than instincts.

Sharot’s next exploration answers an ancient question: how did the ability to imagine the future arise, and what does it have to do with optimism? Through delightful studies involving scrub-jays, voles, and taxi drivers, she traces the biological roots of prospection—the distinctly human skill of traveling mentally through time.

Birds That Plan for Tomorrow

In 2007, behavioral psychologist Nicky Clayton at Cambridge discovered that scrub-jays could anticipate future hunger and strategically cache food where it would be scarce. These birds even re-hid their meals when watched by others—evidence of foresight and social awareness. Such planning contradicts the old “Bischof-Köhler hypothesis,” which claimed nonhumans were mentally stuck in the present. Sharot uses Clayton’s clever experiments to show that the seeds of optimism may predate humanity itself: creatures capable of envisioning tomorrow are already primed for hope.

The Brain’s GPS: The Hippocampus

Cognitive time travel depends on the hippocampus—a structure essential for both memory and imagination. London taxi drivers who master “The Knowledge,” memorizing 25,000 city streets, show enlarged hippocampi that grow with experience, much like food-storing birds whose hippocampi expand during fall caching season. Sharot uses this parallel to argue that memory evolved partly to simulate the future, not just recall the past. Our brains reuse old experiences as ingredients for new possibilities, blending fragments of personal history into imagined outcomes.

Conscious Time Travel and Its Costs

Humans have a unique twist: our large frontal lobes allow self-awareness, letting us project ourselves far ahead—but also confront the inevitability of death. Sharot cites biologist Ajit Varki, who argues that this awareness could have caused species-wide despair if not paired with optimistic denial. Evolution selected for brains able to foresee mortality yet believe in immortality through legacy or renewal. Thus, consciousness and optimism are intertwined gifts: survival requires both realism and hope.

From the scrub-jay to the philosopher, Sharot concludes, the power to imagine the future demanded optimism as its emotional shield. Without a brain wired for hopeful anticipation, species capable of foresight might have perished under the weight of their awareness.

In one of the book’s most empowering arguments, Sharot demonstrates that optimism doesn’t merely color perception—it actively changes outcomes. Through the story of basketball coach Pat Riley’s audacious championship guarantee, she explains how belief turns into behavior and behavior into results.

Optimism in Action: Pat Riley’s Promise

After the 1987 NBA Finals, Riley publicly promised that his Los Angeles Lakers would win again. His guarantee created a psychological shockwave: players trained harder, fans believed fiercely, and the prophecy fulfilled itself. Sharot ties this to sociologist Robert Merton’s definition of a self-fulfilling prophecy—a false belief that becomes true because it changes behavior. Optimism, she shows, is causal, not decorative; it drives motion toward imagined goals.

Expectation Shapes Performance

In education, psychologist Robert Rosenthal’s “Pygmalion effect” revealed that teachers who expected higher performance from randomly selected students unwittingly boosted their IQ scores. Similarly, stereotypes, whether positive or negative, mold real outcomes. When Iowa teacher Jane Elliott divided her class by eye color, declaring one group superior, children’s measured intelligence shifted within hours, proving how deeply expectation alters cognition. Sharot enriches these examples with neuroscience: the frontal cortex lights up when we confront mismatches between expectation and result, helping us learn and adapt.

The Biology of Hope

Sharot cites neuroscientist Sara Bengtsson’s fMRI study showing that people primed with positive words like “clever” produced stronger frontal-lobe error signals during tasks—they cared more about mistakes and improved faster. Conversely, those primed with “stupid” showed no change, accepting failure passively. Optimism, then, sharpens learning by making the brain anticipate success and correct errors accordingly. This mechanism unfolds throughout life—from patients recovering faster after heart surgery to optimistic law students earning higher incomes (a correlation also noted by psychologist Martin Seligman).

Sharot’s conclusion: hope is biological. The brain’s reward circuits motivate persistence when the future feels promising, while pessimism shrinks effort and lifespan. Expectation, whether in classrooms or cardiac wards, becomes destiny because the brain behaves in accordance with its predictions.

Sharot distinguishes between optimism’s adaptive side and its dark edge. In times of crisis—from the Great Depression to the 2008 recession—optimism proved both a balm and a blindfold. Her portraits of Barack Obama’s uplifting speeches and Shirley Temple’s cheerful films show how collective hope can heal nations, yet also obscure looming danger.

Private Optimism vs. Public Despair

Humans, Sharot observes, typically trust their personal future more than their society’s. Even amid political chaos, most individuals imagine personal success and health. Surveys in Britain showed that while citizens believed the NHS was collapsing, 80% were satisfied with their own local hospitals. This paradox—optimistic self-perception but pessimistic national view—stems from perceived control. You assume you can influence your own health choices, but not government policy.

The Power of Relativity

Sharot explains that optimism thrives on comparison. Believing your personal situation is better than average boosts pride and comfort. Conversely, during global downturns, optimism scales up—when everyone suffers, communal hope returns because improvement requires collective recovery. That’s why Obama’s 2008 election ignited world optimism in the midst of economic collapse: desperation enhances receptivity to hope.

When Hope Turns Hazardous

Yet optimism can breed negligence. Stalin ignored warnings of Hitler’s plans; investors dismissed risk in housing markets. Unchecked optimism undermines risk management, turning belief into peril. Sharot calls this duality “red wine optimism”—a glass a day sustains health, but a bottle destroys it. The healthiest mind, she argues, balances faith with evidence, cultivating moderate optimism that motivates progress without distorting realism.

Sharot’s message: optimism is vital, but awareness of its bias prevents catastrophe. You should savor its benefits while occasionally checking the data.

Can you predict what will truly make you happy? Sharot challenges everyday assumptions about wealth, children, marriage, and health, showing that people consistently misjudge the ingredients of happiness. Underlying these misjudgments is the same cognitive bias that drives optimism—a brain that highlights positives and downplays negatives.

Misplaced Pursuits

According to global surveys, most people believe more money or better health will make them happier. Yet data shows that lottery winners return to baseline contentment within a year, and parents report lower daily happiness while raising children. Instead, simple acts—gardening, kindness, and community—predict greater well-being. Sharot references Nobel laureate Daniel Kahneman’s research, which measured moment-by-moment happiness and found chores and commutes often less aversive than childrearing stress!

The Brain’s Positive Filter

Why do we nonetheless chase mistaken goals? Because the brain’s reward circuits—especially dopamine pathways in the striatum and frontal cortex—inflate the subjective value of anticipated rewards. Sharot’s imaging work shows that when people imagine desirable futures, emotional centers activate more vividly than when picturing negative ones. This neural asymmetry is the optimism bias made visible.

Depression: Broken Optimism

Clinically depressed individuals display the opposite pattern: hypoactivity in the rostral anterior cingulate cortex weakens emotional regulation, making bleak outcomes seem more vivid and believable. Sharot quotes psychologist Rollo May: “Depression is the inability to construct a future.” From this perspective, optimism isn’t naive—it’s the brain’s built-in antidepressant, keeping our gaze forward.

Understanding how your mind mispredicts happiness helps you focus on choices—gratitude, social connection, purpose—that sustain genuine joy beyond temporary pleasure. As Sharot concludes, chasing happiness does less than believing happiness is coming soon.

Sharot explores how optimism buffers us against fear and depression by changing how we interpret setbacks. Through stories of loss, trauma, and resilience—from accident survivors to deep brain stimulation patients—she shows that optimistic cognition rewires emotional circuits.

Depression and Pessimistic Explanations

When bad things happen, people explain them differently. A pessimist like Fred (in Sharot’s example) blames himself permanently: “All my relationships will fail.” An optimist like Shawn sees problems as temporary and external. This difference determines emotional recovery. Martin Seligman’s research on dogs revealed the principle of learned helplessness: after repeated uncontrollable shocks, some dogs stopped trying to escape. Humans similarly become passive when they see adversity as inevitable. Cognitive training can reverse this pattern by teaching individuals to reinterpret events and regain control.

Neural and Genetic Foundations

Sharot connects psychological resilience to biology. Serotonin levels and gene variants determine susceptibility to depression: carriers of short alleles of the serotonin transporter show heightened fear responses and reduced communication between the amygdala and frontal cortex. In contrast, long alleles correlate with optimism and attentional bias toward positive stimuli. Treatments—from antidepressants to deep brain stimulation—target these circuits, restoring balance and optimism.

From Darkness to Spring

One of Sharot’s most moving accounts is Helen Mayberg’s pioneering surgery for severe depression. When electrodes stimulated patients’ subgenual cingulate cortex, the first reaction wasn’t euphoria but calm—the “first day of spring,” as one patient described. Sharot interprets this as the biological signature of optimism returning: balance restored between emotion and expectation.

By teaching the mind to reinterpret pain, whether through therapy or technology, we can turn adversity into growth—the brain’s modern philosopher’s stone.

In her final chapters, Sharot confronts optimism’s paradox: our refusal to see danger often endangers us, yet that very blindness sustains progress. From Stalin’s dismissal of invasion warnings to financial analysts ignoring risk before the 2008 crash, she illustrates optimism’s destructive potential when collective illusions amplify.

Selective Learning

Using her own fMRI research, Sharot shows that the brain literally filters information to protect hope. When given statistics about disease or divorce, people update beliefs only if the news is better than expected. The frontal lobes display strong error signals for positive surprises but weak ones for negative feedback. In other words, we learn from good news and ignore bad—an asymmetry hardwired into neural computation.

Practical Consequences

This distortion explains personal and social misjudgments: overconfidence in marriage longevity, underestimating health risks, and poor planning in public projects like the Sydney Opera House, which ran 1,400% over budget. Sharot cites economists Manju Puri and David Robinson, who found moderate optimists make better financial decisions—saving more and smoking less—while extreme optimists make reckless ones.

Balancing Illusion and Insight

Sharot’s closing analogy compares optimism to red wine: one glass daily sustains well-being, but a bottle corrodes judgment. Awareness, not abstinence, is the cure. Like trained pilots trusting instruments over perception, we can enjoy the motivating glow of optimism while counterchecking evidence before major choices. Recognizing the bias lets us harness hope without falling victim to delusion.

Sharot’s optimism itself is cautious yet constructive: human progress depends on seeing the world as better than it is—just not too much better. Hope, she concludes, is both the brain’s greatest deception and its most essential truth.