Knowledge that Transforms

In recent years, several scholars have argued that the influence of deliberate practice on expertise has been overstated. Others have contended that these critiques conflate deliberate practice with less effective forms of training. We analyzed a large, longitudinal cohort of Chess.com players ( N = 44,213) using objective, time-stamped measures of both practice activity and performance. We tested whether deliberate practice-aligned activities predict greater rating improvement than playing games. Multilevel models revealed that, despite more than 90% of player time being spent on games, deliberate practice was substantially more efficient for learning. Although not all deliberate practice-aligned activities were equally effective, the category as a whole was associated with a 3.61× advantage in learning efficiency relative to gameplay ( p s < .001). These findings offer rare real-world evidence in a long-standing theoretical debate about learning efficiency. How individuals train, not just how much, fundamentally shapes the trajectory of skill development.

How does the mind grow? Despite centuries of philosophical and psychological inquiry, little is known about how ordinary people intuitively conceptualize mental development. Across six countries (Australia, Japan, Mexico, South Africa, the United Kingdom, and the United States), adult participants reported their intuitions about mental development by indicating when they think various mental capacities first emerge. Across tasks and cultures, intuitions about mental development were consistently organized along two dimensions: an earlier-developing perceptual and experiential dimension (e.g., seeing, fear, hunger, pain) and a later-developing reflective and evaluative dimension (e.g., reasoning, beliefs, self-restraint, pride). Competing models were ruled out, showing that this structure is unique to lay beliefs about mental development. These dimensions also aligned with participants’ intuitions about the origins of mental capacities within a nature–nurture framework. Together, the findings reveal a consistent cross-cultural pattern for reasoning about mental development and illuminate the intuitive architecture of mind perception.

Does overconfidence really confer adaptive benefits to children’s learning? Through a tripartite investigation involving a preregistered replication (Study 1; N = 30, children aged 6–8 years), computational simulation (Study 2), and an experimental intervention (Study 3; N = 64, children aged 6–8 years), we first replicated previous findings that highly overconfident (HO) children exhibited less negative performance change across a memory task than their low-overconfidence (LO) counterparts. However, this pattern was driven by participant-selection bias and regression-to-the-mean effects rather than by adaptive benefits of childhood overconfidence. When experimentally manipulating children’s overconfidence levels to eliminate these methodological drawbacks, the difference in performance changes between HO and LO children disappeared. These findings challenge an influential hypothesis about the adaptive nature of childhood overconfidence, underscore the risks of median-split designs with difference scores, highlight the necessity of causal experimental approaches in developmental research, and raise concerns about educational practices promoting positive illusions in children.

Advances in AI have enabled chatbots to provide warm, personalized support. Yet little is known about the long-term consequences of AI companionship. Across a 12-month longitudinal study with more than 2,000 adults from four Western countries, we examined the bidirectional relationships between social chatbot use and loneliness.We found evidence that increased social chatbot use predicted increased loneliness, using a single-item measure of emotional isolation. When we used a broader and more stable measure of social connection, we found evidence that feeling less socially connected predicted subsequent increases in social chatbot use; however, chatbot use did not significantly predict decreases in social connection. Taken together, these findings provide initial evidence that being lonely may spur people to seek companionship through chatbots but that such use may, over time, exacerbate feelings of loneliness. We urge caution, however, in drawing strong conclusions given the exploratory nature of our analyses.

Accountability is a commonly recommended intervention to reduce discrimination. However, there have been no field experiments testing whether it reduces discrimination in workplaces. Here we present preregistered analyses of a field experiment conducted at a company ( n = 3,266 managers rating 17,149 employees) testing whether an accountability intervention reduces performance-evaluation gaps between White and racial-minority employees. We did not find evidence that the accountability intervention closes evaluation gaps. These null effects are likely not driven by a lack of statistical power or by inattentive managers, nor is the manipulation ineffective in all contexts—a supplemental online experiment shows that similar treatment language does change decision-making, underscoring a disconnect between findings in hypothetical settings versus real organizations. These results highlight the need for additional field experiments and theorizing to better understand when and why accountability interventions, as they may typically be implemented in organizations, improve diversity-related outcomes.

How essential is a sense of significance for motivation—the feeling that our efforts matter beyond the trivial or momentary? Four studies ( N = 604, children aged 4–9 years of age and 582 adults) show that no amount of significance is too small to matter, even for small actions from early in life. Children and adults strongly preferred artistic activities with minimal significance (i.e., where their work would be saved) over activities with no lasting existence. This preference held for both repetitive and one-time tasks and was specific to creating artwork, not just observing it. Anticipating even minimal significance motivated participants to engage in productive rather than effortless activities. When significance is absent, focusing on enjoying the process partially, but not fully, compensates for motivation. These findings illuminate the scope and sensitivity of significance, revealing it to be not a luxury concern but an essential, early-emerging motivational force in an increasingly fast-paced, transient world.

The cognitive reflection test (CRT) measures reliance on intuitive thinking versus deliberate reasoning and predicts important real-world outcomes. Prior research has suggested that testosterone administration impaired CRT performance, but follow-up studies produced null results. To provide a rigorous test, we conducted a large, preregistered, double-blind, placebo-controlled experiment, unprecedented in size, with 1,000 adult men, as part of an adversarial collaboration. Participants received a single dose of intranasal testosterone or placebo, completed the CRT, and rated their confidence level. We found an insignificant treatment effect on the CRT, with the point estimate in the opposite direction of the original hypothesis (β LOGIT = 0.118, 95% confidence interval (CI) = [−0.099, 0.335]). In a second primary test, we found a significant negative treatment effect on confidence (β LOGIT = −0.329, 95% CI = [−0.558, −0.100]), which is also the opposite of our prediction. Our findings challenge earlier claims about testosterone’s cognitive effects and highlight the importance of high-powered replications. Long-term or developmental testosterone effects remain potentially important but difficult to study.

Researchers have long debated whether self-esteem is associated with aggression. In this preregistered research, we tested the effects of self-esteem on aggression by using statistical models that control for unmeasured time-invariant confounders. Data came from a multi-wave longitudinal study of 674 Mexican-origin families, including multi-informant assessments of children, mothers, and fathers at 1- or 2-year intervals. There was no evidence of systematic self-esteem effects on aggression, and the results held when we controlled for narcissism and when the influence of shared-method variance could be ruled out. Also, there was little evidence for effects in the reverse direction, that is, from engaging in aggression on self-esteem. One limitation was that in most cases it was not possible to test whether the self-esteem effects were curvilinear because of the nonconvergence of these models. Overall, the findings do not support either low or high self-esteem as a risk factor for aggression.

We present the results of a replication of Study 2 from Ariely and Wertenbroch on the role of deadlines in mitigating procrastination. We show that our results do not replicate those of the original article. In our replication, with adult participants enrolled at a large public university in the United States, changes in the deadlines had a negligible effect on the three performance metrics and several survey metrics used in the original study. Evenly spaced deadlines, externally imposed on participants by the experimenters, did not stand out for their effectiveness in reducing procrastination in participants. The data further indicate consistency with several patterns of participant behavior that should be expected irrespective of our main replication results.

Resource constraints in neural information processing imply that numerical discriminability optimally adapts to the frequency of numerical magnitudes in a decision maker’s environment. Here, we tested the economic consequences of efficient numerical range adaptation in representative samples of the United Kingdom and Japan ( N = 2,309) and in a replication in Austria and Hungary ( N = 607). We exploited natural variation in currency units and combined it with an orthogonal variation in experimental currency units to detect the effect of habitual versus nonhabitual numerical ranges on the incidence of errors in decisions under risk. The results highlight the direct economic importance of numerical adaptation, thus calling into question standard assumptions that choice quantities are perceived without noise.