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Performance factors affect both the expression of an existing understanding and, potentially, the experiences through which that understanding emerges. These are different causal claims. An expression account says that a <child> represents an agent's mistaken <belief> but fails to demonstrate it because the task overloads <language>, <Memory in animals>[memory], response selection or <Inhibitory control>[inhibition]. An emergence account says that developing those capacities helps construct increasingly flexible representations of <belief>. The same association between executive control and <false belief> performance is compatible with either account; a discriminating argument must examine manipulations, time course and transfer.
The classic unexpected-transfer procedure, associated with <Heinz Wimmer> and <Josef Perner>'s 1983 study, makes the diagnostic contrast clear. A protagonist leaves an object in one location, does not witness its displacement, and returns. Predicting the protagonist's initial search requires distinguishing the protagonist's representation from the <child>'s own knowledge of reality. A traditional failure might reflect treating <belief> as reality, but it might also reflect misunderstanding the request, forgetting the agent's informational access or selecting the salient actual location. <Memory in animals>[Memory] and reality-control questions help verify story comprehension without eliminating every demand of coordinating the representations.<Beliefs about beliefs by Heinz Wimmer and Josef Perner>[Cognition 13, 103–128; unexpected-transfer stories]{ref}
Conversational evidence particularly supports expression. <Michael Siegal> and <Karen Beattie> clarified that the question concerned where the protagonist would look \i[first]. Three-year-olds were more successful when the intended initial-search interpretation was made explicit. A <child> answering the actual location to an ambiguous request may be giving helpful advice about where to find the object, rather than revealing an inability to represent a mistaken <belief>. Because the conceptual relation can remain unchanged while wording changes, the result demonstrates a task contribution. It does not establish that every younger <child>'s standard-task error has that pragmatic origin.<Where to look first for children's knowledge of false beliefs by Michael Siegal and Karen Beattie>[Cognition 38, 1–12; initial-search wording manipulation]{ref}
<Peipei Setoh> and colleagues separated two concurrent demands in a picture-book procedure. Two-and-a-half-year-olds followed an illustrated search story in which the object was taken away, reducing the lure of a known competing location. Interspersed “where” practice questions about familiar pictures reduced response-generation demands without directly teaching a <false belief> answer. In the first experiment, 25 of 32 <children> selected the belief-consistent container. Further experiments varied the practice procedure; when inhibitory demands were increased, response practice was insufficient. The conjunction is informative: failure can result from interacting demands, so removing one demand need not rescue performance if another remains high.<Two-and-a-half-year-olds succeed at a traditional false-belief task with reduced processing demands by Peipei Setoh and others>[PNAS 113, 13360–13365; Experiments 1–4 and picture-book apparatus]{ref}
These findings make a purely stage-like inference from standard failure to complete conceptual absence untenable. However, scaffolded success does not prove fully adult-like, context-independent competence. A modified task may supply external support that is part of the solution, and repeated practice may change strategy during the test. Strong expression evidence preserves the false-belief-versus-reality contrast, avoids location cueing and response coaching, and tests transfer to new agents, stories and response formats. Task simplification that removes the need to represent another person's mistaken <belief> would not be diagnostic.
Nonverbal <infant> studies extend the argument but increase the measurement burden. <Kristine H. Onishi> and <Renée Baillargeon> used a staged apparatus containing green and yellow boxes and a hidden toy. The actor's visual access to the toy's movements produced true- or <false belief> conditions, after which she reached into a box. Fifteen-month-olds looked longer at belief-incongruent reaches. The factorial manipulation is more informative than a single surprising action because it distinguishes the <infant>'s knowledge of the toy's location from what the actor witnessed. Removing the verbal question is consistent with an expression limitation in older traditional tasks.<Do 15-month-old infants understand false beliefs? by Kristine H. Onishi and Renée Baillargeon>[Science 308, 255–258; green/yellow boxes, true- and false-belief induction and test reaches]{ref}
Nevertheless, looking longer is an indirect dependent measure. <Belief> attribution must be distinguished from remembered action–location associations, novelty and other expectations about behaviour. <Sebastian Dörrenberg> and colleagues tested four nonverbal measures in 66 twenty-four-month-olds. <Anticipatory looking> and interaction results did not reproduce earlier effects, other measures showed order-sensitive evidence, and there were no systematic intertask <correlations>. This does not demonstrate that <infants> lack every belief-related expectation. It weakens the claim that all such measures reveal a single, robustly measured competence already complete in infancy. Low individual-level <Measurement reliability>[reliability] can itself attenuate intertask <correlations>, so absence of convergence is a warning about the measures, not decisive proof of conceptual absence.<How (not) to measure infant theory of mind by Sebastian Dörrenberg and others>[Cognitive Development 46, 12–30; four measures in 66 two-year-olds, abstract and convergent-validity analyses]{ref}
Evidence for emergence is stronger when developing another capacity changes performance beyond an immediate response aid. <Courtney Melinda Hale> and <Helen Tager-Flusberg> randomly assigned sixty preschoolers who failed initial <false belief> and complement tests to training on <false belief>, <sentential complements> or relative clauses. Complement training improved both the trained <language> skill and several <theory of mind> posttests; relative-clause training did not produce the same transfer. Complement <syntax> can represent a report such as “she says that the toy is in the box” without requiring the embedded proposition to be true, providing a plausible representational tool. But <false belief> training improved <theory of mind> scores without improving complements, so the study does not establish that mastery of that <syntax> is a necessary prerequisite.<The influence of language on theory of mind by Courtney Melinda Hale and Helen Tager-Flusberg>[Developmental Science 6, 346–359; random allocation to complement, false-belief or relative-clause training]{ref}
The emergence interpretation must also be calibrated. The posttests followed training over a short interval, so improved coordination or access remains an alternative to a new concept. More persuasive evidence would show retained gains across untrained measures and environments, with reliable baseline assessment. Conversely, an expression-only theory cannot explain every developmental change merely by labelling poor performance a load effect: it must specify the required representation, quantify the demands and predict when targeted reductions should help or fail.
An integrated account is therefore best supported. <Language> and executive control can enable <children> to acquire, compare and discuss conflicting perspectives over development; the same capacities then determine whether a representation can be accessed and translated into the demanded answer on a particular trial. A low-load success establishes an ability under supportive conditions. A later high-load success demonstrates more independent and flexible deployment, which is itself a developmental achievement. Short-term demand manipulations primarily test expression; longitudinal and training designs can constrain emergence, provided they separate conceptual change from strategy and practice. The evidence supports contributions from both rather than an unrestricted conclusion of either complete competence from infancy or wholly absent understanding before conventional task success.
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