The Confidence Code: The Science and Art of Self-Assurance – What Women Should Know

Journalists Katty Kay and Claire Shipman argue that a measurable "confidence gap" between men and women holds women back from reaching their full potential, even as women's competence and credentials have never been stronger. Drawing on neuroscience, genetics, psychology, and interviews with high-achieving women, the authors contend that confidence is not merely a personality trait but a catalyst for action, and that women can deliberately cultivate it through risk-taking, failure, and authentic self-expression.

Kay and Shipman trace their investigation to patterns they noticed while writing their previous book, Womenomics (2008): Accomplished women routinely expressed self-doubt, attributing successes to luck and deflecting credit. The authors admit to the same tendencies and set out to ask whether women are really less confident than men, what confidence actually is, and whether it can be acquired.

The authors establish the scope of the gap through research and interviews. They visit a Women's National Basketball Association (WNBA) practice session, where elite players describe overthinking and people-pleasing in ways their male counterparts do not. Christine Lagarde, head of the International Monetary Fund, confesses to obsessive overpreparation and reveals she and German Chancellor Angela Merkel share this habit. Quantitative evidence reinforces the pattern: A Hewlett-Packard internal study finds women apply for promotions only when they meet 100 percent of the qualifications, while men apply at 60 percent. Research by Cornell psychologist David Dunning and University of Washington psychologist Joyce Ehrlinger shows women rate their scientific abilities lower than men despite scoring nearly identically on tests. UC Berkeley psychologist Cameron Anderson's research delivers a striking finding: Confidence matters more than competence for achieving social status and influence.

Having documented the gap, the authors define confidence precisely. They distinguish it from self-esteem, a stable sense of self-worth not necessarily tied to action; optimism, a positive outlook that does not require doing anything; self-compassion, pioneered by University of Texas professor Kristin Neff, which supports risk-taking by cushioning failure; and self-efficacy, a belief in one's ability to succeed at specific goals. Ohio State University psychology professor Richard Petty supplies the definition the authors adopt as their organizing principle: "Confidence is the stuff that turns thoughts into action" (62). This definition clarifies why women's tendency to overthink and hold back is so damaging.

The authors investigate whether confidence is genetic. Neuropsychologist Steve Suomi at the National Institutes of Health has studied a colony of rhesus monkeys for over 40 years and concludes that some are born with greater confidence, linked to the serotonin transporter gene. Behavioral geneticist Robert Plomin at King's College London conducts a 20-year study of 15,000 sets of British twins and finds that children's self-perceived ability predicts academic achievement more significantly than IQ, suggesting the genetic contribution to confidence may be as high as 50 percent. Three neurotransmitters prove critical: Serotonin promotes calm decision-making, oxytocin encourages social connection, and dopamine drives risk-taking. The COMT gene's "warrior" and "worrier" variants help explain why some people thrive under pressure while others falter.

The genetic picture, however, is not deterministic. The authors explore epigenetics, the field studying how life experiences alter gene expression. Suomi's cross-fostering experiments show that anxious monkeys raised by nurturing mothers not only overcome their genetic predisposition but outperform their genetically resilient peers. This leads to the "orchid theory," proposed by developmental psychologist Bruce Ellis and pediatrician W. Thomas Boyce: Some children are dandelions, hardy in most environments, while others are orchids, more sensitive and capable of exceptional thriving or dramatic failure depending on nurture. Research on brain plasticity provides further hope. MRI studies show that eight weeks of meditation can shrink the amygdala, the brain's fear center, and increase activity in the prefrontal cortex, the region responsible for calm reasoning. Cognitive neuroscientist Laura-Ann Petitto of Gallaudet University explains that new neural pathways can be built over old ones at any age.

The authors examine the societal and biological factors that compound the genetic picture. Girls are trained from a young age to be compliant and cooperative, behavior rewarded in school but counterproductive for building resilience. Research shows that boys attribute failure to lack of effort, while girls interpret failure as reflecting a lack of skill. Stanford psychologist Carol Dweck observes that the meritocratic classroom does not prepare girls for a competitive workplace. Sports participation, a proven confidence builder, remains uneven: Girls are six times more likely than boys to drop off teams. In the workplace, both men and women penalize women who talk more in meetings, and BAE Systems CEO Linda Hudson observes that men are assumed competent until proven otherwise, while women face the reverse presumption. Stereotype threat, in which members of a stereotyped group underperform under the weight of negative expectations, compounds these pressures.

Self-inflicted habits also play a role. Women ruminate excessively, tend to attribute failure to personal inadequacy while crediting success to luck, and resist acting unless they believe they can perform flawlessly. Brain biology adds another layer: Women's brains are more active, particularly in the prefrontal cortex and the limbic cortex, a region involved in processing emotion, producing more overthinking. Women produce 52 percent less serotonin than men and possess a larger cingulate gyrus, sometimes called the worrywart center. Testosterone, 10 times higher in men after puberty, fuels risk-taking, while estrogen encourages bonding and conflict avoidance. The authors note, however, that these differences also confer advantages, and that female hedge fund managers have outperformed their male counterparts.

With the problem mapped, the authors turn to solutions. They argue that confidence requires risk, failure, and persistence rather than hollow praise. Dweck's concept of a "growth mind-set," the belief that abilities can be developed rather than being fixed, is presented as foundational. Senator Kirsten Gillibrand of New York, who spent a decade volunteering and taking classes before feeling ready to run for Congress, demonstrates that confidence can be deliberately built at any point in life. Specific strategies include acting when in doubt, starting with small risks; adopting Silicon Valley's "fail fast" approach of learning from quick, manageable failures; and countering negative automatic thoughts with alternative interpretations. The authors also advise shifting focus from self to team, citing research showing women gain confidence when they frame their work as benefiting others. For parents, the authors prescribe letting children fail and praising specific effort rather than generic ability. For daughters specifically, they advocate avoiding both overcriticism of bold behavior and overpraise of compliance.

The book's final chapter reveals the authors' genetic results. Both carry the "worrier" COMT variant and the short/long serotonin transporter variant, predisposing them to anxiety, along with a favorable oxytocin variant associated with warmth. Dr. Jay Lombard at Genomind tells them he would not have predicted strong natural building blocks for confidence from their profiles alone but emphasizes that genes represent probability, not destiny.

This leads to the book's culminating insight: Confidence in women need not mimic male bravado. The authors argue for a "third way" that includes listening, sharing credit, showing vulnerability, and speaking calmly with conviction. A Stanford Business School study finds that women who combine traditionally masculine traits like assertiveness with feminine ones like collaboration are promoted 1.5 times as often as most men. Lagarde's advice to a new female president captures the idea: "dare the difference" (213) rather than measuring oneself against male predecessors. The authors distill their code to three precepts: Think less, take action, be authentic. They close with the image of WNBA player Crystal Langhorne sinking a layup built on hours of practice, an emblem of confidence that is earned, real, and attainable.