Courage and confidence come from the size of the testicles.
Executive summary
The short answer is: no—courage and confidence are not determined by the physical size of a man’s testicles, although the association is a potent cultural metaphor and there are measurable biological correlations between testis size and reproductive function and some parenting-related behaviors. Linguistic and cultural metaphors tie “having big balls” to bravery [1], but the empirical literature shows testicular volume mainly predicts sperm production and some life-history trade-offs—not a reliable marker of personal bravery or psychological confidence [2] [3].
1. The cultural shorthand: why testicles became a symbol of courage
Across languages and cultures, testicles have been used metaphorically to signify virility, boldness, and risk-taking—English “balls” or “ballsy,” Spanish “cojones,” and similar idioms elsewhere illustrate a long-standing symbolic link between male genitalia and courage rather than a scientific claim about physiology [1]. Popular commentaries and opinion pieces echo and reinforce that metaphor, making the phrase culturally ubiquitous even where no causal mechanism has been proposed [1].
2. What biology actually ties to testicle size
Medical and andrological research finds a clear biological signal: testicular size correlates strongly with aspects of testicular function such as sperm count, sperm concentration, and certain hormone measures, making testis volume a useful clinical index in fertility assessments [2] [4]. Clinical sources caution that very large testicles can indicate pathology and that correlations between size and circulating testosterone are modest at best, so size is not a straightforward proxy for overall male hormonal “dominance” [5] [2].
3. Behavioral correlations are about life-history trade-offs, not moral courage
Evolutionary and neuroscience studies describe trade-offs in reproductive strategy: in humans, larger testicular volume has been associated with reduced nurturing-related brain responses and lower paternal involvement in one imaging/behavioral study, suggesting testis size may reflect mating-versus-parenting tendencies rather than bravery per se [6] [3] [7]. Those findings are correlational, not causal, and researchers emphasize complexity and many social and psychological mediators; they do not claim that men with smaller testes are inherently braver or more confident [3] [7].
4. Cross-species lessons complicate any simple “bigger = bolder” story
Comparative work shows divergent patterns: in some primates a trade-off exists between sperm production (larger testes) and alternative strategies like loud calls—howler monkeys with the loudest vocal displays can have relatively smaller testes—illustrating that sexual selection produces multiple strategies, none of which straightforwardly map onto human psychological traits like courage [8]. Agricultural and animal studies likewise use testis volume to predict sperm output in rams and other species, supporting the reproductive-function interpretation rather than any behavioral universal about courage [9].
5. Popular impressions, surveys and online anecdotes are not evidence
Internet forums, polls and lifestyle articles circulate the belief that genital size predicts personality or boldness, but these are anecdotal, culturally biased and not substitutes for controlled studies [10] [11]. Some media pieces conflate metaphor and biology, which fuels misconceptions that testicular size determines confidence; the peer-reviewed evidence instead points to modest biological correlates with reproduction and parenting roles and warns against overinterpreting those associations [1] [2].
6. Conclusion: metaphor endures, evidence does not support a direct causal link
The enduring phrase “it takes big balls” is powerful rhetoric grounded in cultural symbolism, but scientific studies do not support a simple physiological rule that larger testicles produce greater courage or confidence; instead, testicular size is primarily linked to sperm production and shows some association with mating-versus-parenting trade-offs in behavior—complex, context-dependent patterns that are correlational and not proof that size causes bravery [2] [3] [7]. Where the literature is silent—such as direct, controlled tests of testis size predicting standardized measures of courage or self-reported confidence—no claim can be substantiated from the provided reporting.