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Greater <Research transparency>[transparency] and <Scientific reproducibility>[reproducibility] have changed <developmental psychology>'s estimates, measurement practices and theoretical confidence, but have not simply replaced a collection of “true” findings with “false” ones. <Computational reproducibility> asks whether the same data and documented analysis yield the same result. <Scientific replication> asks what happens with new observations. <Preregistration> makes planned tests distinguishable from exploratory choices; open materials permit checking whether ostensibly similar studies actually use the same procedure. None of these, by itself, guarantees <construct validity> or representative sampling.
The <marshmallow task> illustrates a substantive change in interpretation. <Walter Mischel>'s early experiments offered preschoolers a smaller immediate reward or a preferred delayed reward and manipulated how <attention> was directed during waiting. Distraction increased delay. The original experimental programme therefore already showed sensitivity to cognitive strategy and setting, rather than a fixed quantity of virtue revealed by a treat. Later predictive associations are a different claim from those immediate experimental effects.<Cognitive and attentional mechanisms in delay of gratification by Walter Mischel and others>[Journal of Personality and Social Psychology 21, 204–218; experimental manipulations of attention during waiting]{ref}
<Tyler W. Watts> and colleagues revisited long-term prediction in a larger and more diverse cohort. Their 2018 conceptual <Scientific replication>[replication] used a waiting task at fifty-four months and adolescent achievement outcomes. Associations were substantially reduced after adjustment for family background, early cognitive abilities and the home environment; much of the achievement difference was concentrated at the lowest waiting times. An important measurement difference was the seven-minute ceiling, rather than treating all waiting tasks as interchangeable. These results weaken a simple causal story in which training a preschooler to wait longer should, by itself, transform later attainment. They do not show that <self-regulation> never matters, because adjustment can remove both <confounding> and potentially meaningful pathways.<Revisiting the marshmallow test by Tyler W. Watts and others>[Psychological Science 29, 1159–1177; Delay of gratification measure, adjusted models and measurement limitations]{ref}
<Celeste Kidd> and colleagues supplied experimental evidence for one alternative mechanism: environmental <Measurement reliability>[reliability]. Before the waiting task, <children> encountered an adult who either fulfilled or failed promises about appealing materials. <Children> subsequently waited longer after reliable experiences. The observation matters because apparent “poor self-control” can be an understandable response to expecting that a promised reward will not arrive. This small experiment supports contextual causation under its own conditions, not a claim that all socioeconomic differences in waiting are caused by trust. Together, the studies shift the target from an isolated <child> trait to the interaction between control, expectations and circumstances.<Rational snacking by Celeste Kidd and others>[Cognition 126, 109–114; reliable versus unreliable experimenter manipulation]{ref}
<Neonatal imitation> illustrates why replicability also depends on the inferential contrast. <Andrew N. Meltzoff> and <M. Keith Moore>'s 1977 report described very young <infants> matching facial and manual gestures. In this paradigm an adult models an action and <infant> responses are recorded and coded; the crucial question is whether the <infant> produces a given action preferentially after its matching model, not merely whether the action occurs. An increase in tongue protrusion after interesting stimulation is insufficient unless appropriate nonmatching controls exclude general arousal or exploration.<Imitation of facial and manual gestures by human neonates by Andrew N. Meltzoff and M. Keith Moore>[Science 198, 75–78; modelled facial/manual actions and coded infant responses]{ref}
<Janine Oostenbroek> and colleagues tested 106 <infants> longitudinally with nine social and two nonsocial models at one, three, six and nine weeks. Their broad comparisons did not support model-specific <imitation>, although restricted cross-sections could resemble earlier positive findings. This challenged a general innate-imitation account and highlighted the consequences of selecting particular gestures, ages and contrasts after observing results. Yet the study's breadth also created substantive questions about fatigue, presentation and how each action was scored.<Comprehensive longitudinal study challenges the existence of neonatal imitation in humans by Janine Oostenbroek and others>[Current Biology 26, 1334–1338; nine social and two nonsocial models across four ages]{ref}
The subsequent requested-data reanalysis by Meltzoff and colleagues reported tongue-protrusion matching under pooled-control contrasts and criticised features of the elicitation and scoring procedures. That was not an independent <Scientific replication>[replication]: it reused the same observations. It nevertheless shows the scientific value of access to raw data. The disagreement became one about estimands, comparison sets and measurement sensitivity that another <Preregistration>[preregistered] experiment could adjudicate, rather than an unsupported declaration that one team must be wrong. Evidence for one gesture would also not automatically vindicate a broad, domain-specific <imitation> mechanism.<Re-examination of Oostenbroek et al. (2016): evidence for neonatal imitation of tongue protrusion by Andrew N. Meltzoff and others>[Developmental Science 21, e12609; requested raw data, pooled-control tongue-protrusion analyses and design criticisms]{ref}
<ManyBabies> 1 provides a constructive counterexample to the notion that open developmental research only dismantles effects. In a <Registered report>, an international collaboration used common speech stimuli and prespecified analyses to test infant-directed versus adult-directed speech preferences. The final sample included 2,329 <infants> from 67 laboratories. A preference for <infant-directed speech> survived, while its magnitude varied with age, <language> experience and measurement method. Laboratories used central fixation, head-turn preference or <eye tracking> procedures, making methodological variability an object of analysis. The result supports a reproducible average preference without treating the same <effect size> as universal for every <infant> or cultural setting.<Quantifying sources of variability in infancy research using the infant-directed-speech preference by The ManyBabies Consortium>[Advances in Methods and Practices in Psychological Science 3, 24–52; Participants, preregistered analyses and Discussion]{ref}
Several changes to our understanding follow. First, an established group-level tendency can coexist with weak prediction for an individual <child>. Secondly, stimulus choice, stopping rules, exclusions and coding decisions can change what has actually been measured. Thirdly, heterogeneous outcomes can identify theoretically useful boundary conditions, but a moderator discovered after a failure needs a new test rather than serving as an unlimited excuse. Finally, openly available null results reduce selective visibility of successful studies, improving the evidential base used to build developmental accounts.
The causal claim about reform itself should remain modest. Larger samples, broader recruitment and better controls often accompany <Research transparency>[transparency], so a change in an estimate cannot be attributed uniquely to <preregistration>. A perfectly reproducible analysis can reproduce a biased model, and an underpowered <Scientific replication>[replication] may be inconclusive. <Measurement reliability>[Reliability] and measurement equivalence are especially important for looking-time and single-trial <child> tasks; independent coding and predefined exclusion rules help, but do not establish the intended psychological construct. Open <child> data also require appropriate consent and controlled access where identification is possible; useful <Research transparency>[transparency] need not mean publishing recognisable videos.
By 2022, these developments justified a more conditional developmental science: waiting reflects more than a decontextualised trait; claims of newborn action matching require precise controls; and an <infant> speech preference can be robust while method-sensitive. The main advance is a tighter connection between a theoretical claim, an explicitly defined measure and evidence that others can inspect or independently test. <Research transparency>[Transparency] changes what can be learned from disagreement, while <Scientific replication>[replication] establishes how far a finding travels.
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