The Confidence Code

Have you ever wondered why some people act with effortless certainty while others second-guess every decision? In The Confidence Code, journalists Katty Kay and Claire Shipman set out to understand why women—even the most competent and accomplished—often doubt their worth and hold themselves back. After years of research across neuroscience, psychology, and gender studies, they discovered a startling truth: success correlates less with ability and more with confidence. In other words, confidence isn’t just a nice-to-have trait—it’s the differentiator between those who simply dream and those who do.

Kay and Shipman argue that this invisible force, confidence, is what transforms thoughts into action. It’s a skill—not a genetic gift—that anyone can cultivate. Yet, for a variety of biological, social, and cultural reasons, women disproportionately lack it. When women undervalue their skills or see failure as personal incompetence, they avoid risks, stay silent, or wait until they feel “perfectly ready.” Meanwhile, their male counterparts act—and even when unprepared, they’re rewarded for it. The authors call this persistent imbalance the “confidence gap.”

The Confidence Gap and Why It Matters

The book’s central question drives from a deep paradox: women are more educated and qualified than ever, yet still underrepresented in leadership. Kay and Shipman’s reporting found that competence doesn’t predict success—confidence does. Citing studies from Carnegie Mellon and King’s College London, they reveal that women underrate their abilities and men overrate theirs, but the workplace rewards self-assurance more than accuracy. This dissonance isn’t rooted in ability; it’s rooted in belief. The implications go far beyond the office: confidence influences how much risk you take, how you handle criticism, and even how happy you feel.

The authors realized that confidence is both mental and biological. It intertwines genes, environment, and behavior: some of us may be born more cautious due to brain chemistry, but our upbringing, schooling, and culture often reinforce those instincts. Western societies, for instance, still reward girls for good behavior and perfection, while encouraging boys to be bold and defiant. By adulthood, women have learned that competence should speak for itself—but it doesn’t. The modern woman, they argue, is trapped by what they call “the tyranny of perfection.”

Breaking Down Confidence

Kay and Shipman define confidence simply but powerfully: it’s the belief that you can succeed—and the willingness to act on that belief. It’s not blind optimism or arrogance. In psychology, this overlaps with concepts like self-efficacy (Albert Bandura’s term for believing in your capacity to accomplish goals), but confidence adds a crucial behavioral component: action. It’s less about thinking positively and more about doing courageously. Through research with neuroscientists like Adam Kepecs, who studies confidence in rats, the authors show that confidence has both an objective side (accurate assessment of your abilities) and a subjective side (how you feel about them). For humans, the subjective side often trips women up.

Their formula—think less, act more—captures this distinction. Because women tend to overanalyze and fear mistakes, they get trapped in rumination, losing the opportunity to learn through trial and error. Men, by acting faster (even when wrong), learn more quickly and build authentic self-assurance. As MIT researcher Zachary Estes discovered, women perform equally well as men when required to attempt every question—but if given the choice, they hold back. Confidence, then, grows through doing, not waiting for perfection.

The Biological and Cultural Web

In exploring whether confidence is nature or nurture, Kay and Shipman spent time with geneticists and behavioral researchers who study serotonin, dopamine, and oxytocin—the neurotransmitters shaping calm, motivation, and connection. Genes explain part of our disposition, but the brain’s plasticity—its ability to form new neural connections—means confidence can be built at any age. Culture, however, can either amplify or suffocate those neural seeds. In Japan, struggle is celebrated as part of learning; in America, we pity or rescue those who struggle. The result? Girls grow up believing struggle signals failure, not growth. They aim for flawlessness instead of mastery.

Through stories of IMF chief Christine Lagarde, WNBA players Monique Currie and Crystal Langhorne, and political leaders like Kirsten Gillibrand, the authors show how even women at the highest levels wrestle with self-doubt. Yet their breakthroughs come when they act despite fear. Lagarde, for instance, admits she overprepares for every meeting, but she ultimately succeeds because she shows up anyway—and acts decisively. Confidence, the book insists, doesn’t mean you never feel doubt; it means you move forward regardless.

Why Confidence Is a Skill—and a Moral Imperative

Kay and Shipman see confidence as teachable, even moral. When women lack it, they not only limit themselves but also deprive workplaces, communities, and governments of half their potential talent. Closing the confidence gap isn’t just personal therapy—it’s social progress. Through neuroscience, parenting studies, and examples from classrooms to corporate boardrooms, they argue that letting girls fail, praising effort over perfection, and encouraging risk are the building blocks of real confidence. The book closes by urging women to “choose confidence”: to act without overthinking, to detach self-worth from flawless performance, and to recognize that authenticity—not imitation of male bravado—is the most powerful form of confidence.

In this way, The Confidence Code functions as both a scientific exploration and a rallying cry. It reveals that confidence isn’t an innate gift or masculine trait—it’s a muscle you can train, moment by moment, through action, risk, and honesty. For any woman who has ever thought, “I’m not ready yet,” Kay and Shipman offer liberating evidence: you already are; you just have to begin.

When people picture confidence, they often imagine loud voices and unshakable egos. Yet psychologist Richard Petty told the authors that true confidence is far simpler—and more powerful: “Confidence is the stuff that turns thoughts into action.” It’s what bridges intention and execution. Without it, you may think endlessly but never move; with it, you take imperfect action, learn, and grow.

From Lab Rats to Leaders

Strangely enough, some of the clearest evidence for this idea comes from rats. Neuroscientist Adam Kepecs, who studied “statistical confidence,” trained rats to decide which scent was stronger, rewarding correct answers with water. The bolder rats waited longer—signaling higher confidence in their choice. For humans, the same brain region—the orbitofrontal cortex—acts as our confidence engine. It evaluates uncertainty and enables risk. But unlike rats, we’re plagued by self-reflection, social comparison, and overthinking, which often short-circuit confident action.

This overanalysis trap shows up everywhere: women at Georgetown’s Running Start workshop hesitated to run for student office because they feared being seen as “pushy.” Men, by contrast, acted quickly, blissfully unconcerned about approval. The outcome? Those who acted gained experience and, in turn, real confidence. Confidence, the book suggests, is built on action feedback loops, not waiting until you feel ready.

The Mastery Cycle

Confidence grows through what the authors call the Mastery Cycle: action → mistakes → feedback → improvement → new confidence. Each step reinforces the next. When you act, you risk failure, but you also invite evidence that you can survive it. WNBA star Monique Currie admitted she still beat herself up over missed shots—but learning to “move to the next play” was her greatest mental shift. Likewise, General Jessica Wright, one of the first women to command a U.S. Army combat brigade, confessed she once felt like “a spaghetti bowl of nerves.” Yet she acted anyway, confronting sexism head-on. In both cases, confidence formed after the action, not before.

(Psychologist Albert Bandura’s theories of self-efficacy align closely: our sense of capability grows only when we experience mastery—not when told we’re talented. Praise for effort, not innate skill, fuels persistent action.)

The Thinking Trap

For many women, the biggest enemy of confidence is not ignorance or inadequacy—it’s overthinking. The book’s second chapter, aptly titled “Do More, Think Less,” shows how rumination prevents movement. Women, neurologically and socially, tend to analyze decisions longer, replay failures, and predict rejection. Men, meanwhile, act—sometimes to a fault. Yet research shows that even failed action teaches the brain more than prolonged contemplation. Neuroscientific studies reveal that confidence operates like a muscle: neurons in decision-making centers (the prefrontal cortex) strengthen each time we take action under uncertainty.

By pushing yourself to act even when afraid—raising your hand, volunteering, asking for a raise—you send your brain a powerful message: “I can handle this.” Over time, this rewires self-perception. You stop waiting for permission and start generating momentum. Confidence, in short, is not the reward for success; it’s the prerequisite for it.

Kay and Shipman’s message is liberating: you don’t have to feel confident to act confidently. When in doubt, act first—the confidence follows. As psychologist Martin Seligman’s work on optimism also shows, behavior precedes emotion. Eventually, through repetition, you’ll stop asking whether you’re ready and start realizing you already are.

Some people appear “born confident.” In a way, they might be—partly. Kay and Shipman dive into neuroscience to explore the biological underpinnings of confidence. They meet researchers from the National Institutes of Health studying rhesus monkeys and discover that confidence is partly housed in our DNA, shaped by neurotransmitters like serotonin, dopamine, and oxytocin. Yet biology is far from destiny. Environment, experience, and deliberate practice can literally reshape the brain toward confidence.

The Confidence Genes

Rhesus monkeys share with humans a gene called SLC6A4, which regulates serotonin—the chemical that governs calm and emotional regulation. Monkeys with the more efficient “long” version of this gene socialize freely and take risks; those with short strands hang back and exhibit anxiety. Yet when “anxious” monkeys are raised by nurturing mothers, they become even more confident than their genetically advantaged peers. This phenomenon, dubbed the orchid-dandelion theory, suggests that sensitive individuals can thrive spectacularly in the right environment.

Geneticist Robert Plomin’s twin studies also show that confidence, like personality, is roughly 25–50% hereditary—but the rest is learned. Nature provides the foundation; nurture builds the structure. And thanks to epigenetics—how experience turns genetic switches on or off—your behaviors today can literally rewrite your confidence code.

Neuroscience of Self-Belief

Serotonin helps us stay calm; dopamine fuels curiosity and motivation; oxytocin encourages social bonding and optimism. People with balanced levels of all three have brains wired for resilient action. But neuroplasticity research—especially studies on meditation and cognitive behavioral therapy—shows that we can train these circuits. Simple habits like challenging negative thoughts, practicing gratitude, or visualizing success can strengthen new neural pathways just as physical exercise strengthens muscle.

The book highlights how meditation can shrink the amygdala (the brain’s fear center) and enlarge the prefrontal cortex (the decision center). In one University of Manchester study, after only eight weeks of mindfulness, MRI scans showed quieter fear responses and stronger rational control. In essence, practicing calm helps the brain experience confidence until it becomes natural.

Confidence as Choice

The authors ultimately find that while genes set the baseline, choice sets the direction. Behavioral psychologist Frances Champagne’s work on epigenetics suggests that stress responses and confidence can shift within a single generation, influenced by parenting and environment. Translation: you are not locked into your genetic starting point. Every risk taken, every small victory, and every failure reframed as learning reshapes your confidence pathways. The brain registers mastery, not mythology.

As General Jessell at Columbia’s Mind Brain Behavior Institute told them, understanding confidence at the molecular level has global implications. In societies where people feel “learned helplessness,” change begins with belief in agency. On both a biochemical and cultural level, confidence, it turns out, is humanity’s most renewable resource.

If women are as capable as men, why do they act less confident? The authors expose systemic, psychological, and cultural forces that train girls to be cautious and compliant from childhood. From grade school classrooms to corporate boardrooms, the message to girls is consistent: be good, be perfect, don’t fail. Boys, meanwhile, are told: be bold, take risks, shake it off. That conditioning explains why two employees—Robert and Rebecca, both equally talented—end up in very different places.

Learned Limitation

In school, girls are rewarded for neat penmanship, cooperation, and accuracy. Boys are scolded for rowdiness but simultaneously learn resilience—they fail publicly and recover. When life moves from classrooms to workplaces, these patterns endure. Professor Carol Dweck (author of Mindset) notes that girls often develop a fixed mindset—believing ability is innate—while boys grow up with a growth mindset, seeing struggle as proof they’re learning. Adults unconsciously reinforce this divide: we praise girls for being “good” and boys for being “brave.”

At Yale, business professor Victoria Brescoll found that even powerful women talk less in meetings than men of equal rank. Why? Because both men and women penalize outspoken women as “controlling” or “unlikeable.” Men, by contrast, gain status when they speak assertively. This “likeability penalty” traps women between confidence and backlash. As IMF director Christine Lagarde quipped, “If you look like a jerk, you fail; if you look too nice, you fail.”

Stereotype Threat and Self-Silencing

Claude Steele’s research on stereotype threat shows how awareness of bias undermines performance. In one study, Asian-American women performed worse on math tests when reminded of their gender, but better when reminded of their ethnicity. Simply expecting to be judged through a negative lens drains mental bandwidth. Similarly, many women avoid visible leadership not because they lack ambition, but because they worry about social costs—being disliked, rejected, or isolated.

Even physical appearance affects women’s confidence. Studies cited in the book show that women who perceive themselves as “overweight” report lower self-worth, while comparable men experience no penalties. Too often, women over-focus on external validation—praise, beauty, approval—rather than internal satisfaction. The consequence: chronic self-monitoring and hesitation.

Rethinking What Confidence Looks Like

Kay and Shipman stress that women need not imitate male aggression. Instead, the future lies in authentic confidence—self-assurance grounded in empathy, collaboration, and integrity. Studies from Stanford show that women who blend “feminine” traits (humility, cooperation) with “masculine” ones (assertiveness, ambition) outperform everyone—including men. Senator Kirsten Gillibrand embodies this: she rejects the notion that success requires arrogance, insisting that confidence means using your voice in service of others. When women redefine confidence on their terms, they stop chasing approval and start shaping results.

Ultimately, the gap isn’t lack of ability—it’s the compound effect of perfectionism, fear of judgement, and cultural stereotypes. As Kay and Shipman conclude, “Women don’t need to be more competent. They need to be more confident.”

If confidence can be learned, how do we teach it—to our children and to ourselves? The authors argue that the new nurture must be tougher, freer, and more failure-friendly than modern parenting allows. For decades, the “self-esteem movement” encouraged praise and protection. The result? Overpraised but underprepared kids—especially girls—who equate perfection with worth. Kay and Shipman propose a new model rooted in resilience, struggle, and independence.

The Power of Struggle

Psychologist Jim Stigler’s studies in Japan found teachers deliberately assign slightly too-hard problems. Students struggle publicly until they succeed, learning that effort—not talent—matters. Contrast that with American classrooms, where mistakes are seen as failure. Teaching kids to persist through difficulty—what Japanese culture calls gaman—instills real confidence. Failing early, failing small, and recovering quickly inoculates children against later setbacks.

Dermalogica founder Jane Wurwand’s story illustrates this truth. At four, she walked home alone from school. As an adult, she credits that early independence with the belief that she could handle life. Her advice to parents: make kids do small, practical tasks—fry an egg, take the bus, fix a button. Independence, not indulgence, breeds confidence.

Perfection, Praise, and Pressure

Blanket praise (“You’re the best ever!”) does more harm than good. Psychologist Nansook Park says praise should be specific and effort-based: “I like the way you set the table.” This teaches ownership and growth. When children are always told they’re perfect, they avoid challenges that threaten that image. The same logic applies to adults: overprotecting yourself from failure keeps you from mastery. As Elaine Chao, former U.S. Labor Secretary, told the authors, “Some adversity, if it doesn’t break you, makes you stronger.”

Raising Confident Girls

Girls, especially, need room to rebel. Encouraging “goodness” too rigidly breeds perfectionism later. Kay and Shipman advise letting daughters be a “little bad”: interrupt, disagree, even make messes. This teaches agency. For example, Michelle Rhee—former D.C. school chancellor—was labeled “difficult” as a child, but that outspokenness propelled her to leadership. Likewise, letting girls play sports helps them practice risk and loss early, building resilience they’ll later need at work.

Confidence, in essence, thrives on friction. Whether in childhood or adulthood, it develops only through struggle, effort, and risk. As the authors put it, “You build it by doing.”

One of the most transformative ideas of The Confidence Code is the Silicon Valley mantra to fail fast. Instead of fearing mistakes, embrace them as rapid feedback. Entrepreneurs use it to innovate; women can use it to grow. Failure, Kay and Shipman argue, isn’t a verdict—it’s a process of calibration. Each small stumble desensitizes the fear that holds you back, freeing you to act boldly.

Turning Failure into Data

Tech startups release imperfect prototypes, learn what doesn’t work, and adjust. Women, conversely, wait for perfect readiness. By reframing failure as data, not disaster, you recover faster and learn more. Jane Wurwand recalls the day she left an unhappy marriage with nothing but two plastic bags of clothes. It was terrifying—but surviving it made her fearless. Her takeaway: “If I can live through that, I can live through anything.”

From Rumination to Rewiring

Women’s biggest barrier isn’t failure—it’s ruminating about failure. Neuropsychologist Laura-Ann Petitto describes how repetitive negative thoughts carve deep neural highways that perpetuate anxiety. But each positive action—public speaking despite nerves, asking for feedback, applying again—creates alternate routes, eventually rerouting thought patterns toward resilience. This is neuroplasticity in action. The difference between confident and unconfident women isn’t how many times they fail, but how quickly they recover.

The authors even suggest symbolic ways to silence mental “NATs” (negative automatic thoughts)—write them down, then literally throw them away. It’s a small act that reinforces the brain’s capacity to discard unhelpful patterns.

Action Over Perfection

Failing fast isn’t carelessness; it’s disciplined experimentation. At its core lies humility—the willingness to learn from error. Confidence emerges not from flawless performance but from knowing you’ve survived missteps before. Journalist Claire Shipman’s experiment of giving a speech without notes, even if imperfect, taught her that “winging it” with authenticity beats mechanical perfection. As she says, “The confidence came after, not before.”

Failure, then, becomes a training ground. Each quick recovery builds the reflex of self-trust, the ultimate goal of confidence. Failure doesn’t define you—it refines you.

At the heart of Kay and Shipman’s message is a crucial distinction: real confidence doesn’t mean becoming someone you’re not. It means embracing your strengths and daring to act authentically. The book’s final chapter, inspired by IMF leader Christine Lagarde’s phrase “dare the difference,” celebrates female confidence that looks and feels uniquely feminine—not performative masculinity.

Confidence Doesn’t Have One Look

In traditional workplaces, confidence is often equated with dominance: loud voices, physical space, quick decisions. Kay and Shipman urge women to redefine the metric. Confidence can be quiet, collaborative, and composed. Valerie Jarrett, senior adviser to President Obama, described how she learned to speak selectively and powerfully, not constantly. Similarly, Linda Hudson, the first female CEO of a major defense company, exudes authority through calm precision rather than volume.

Stanford research confirms this hybrid approach: women who pair assertiveness with empathy (the so-called “feminine edge”) win more promotions than either highly aggressive men or overly cautious women. The lesson: confidence expressed through authenticity amplifies, not diminishes, your power.

Be Authentic, Not Perfect

Authenticity requires vulnerability—the courage to admit imperfection without self-defeat. Lagarde admits she still feels nervous before high-stakes meetings. What matters is that she shows up anyway. The authors show how women, unlike men, often seek to hide weaknesses, afraid it will undermine credibility. Yet transparency builds trust and authority. As they write, “The truly confident can afford to be real.”

Confidence also requires aligning your values with your behavior. IMF research and leadership psychology both confirm that when your outward actions match your inward beliefs, you project credible authority. Pretending confidence, paradoxically, erodes it. Acting authentically, on the other hand, strengthens the internal circuit of self-trust.

Confidence as a Collective Act

Kay and Shipman end not with individual triumph but collective purpose. Confidence grows when women help other women—by giving honest feedback, suggesting risk, or naming each other’s achievements out loud. As Christine Lagarde does with her “List” of talented women, amplifying others multiplies confidence across networks. The authors remind readers that confidence doesn’t compete; it compounds.

Ultimately, to “dare the difference” means embracing your distinctness as your power source. Confidence is a choice you make each day—to act, fail, and rise as yourself. Not to imitate anyone else, but to finally trust that who you are is already enough.