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Question

Difficulty: Very hardSampling and Survey Flaws

Linguist: To determine whether early exposure to multiple languages enhances cognitive flexibility, researchers tracked two groups of children over ten years: one group raised in bilingual households and another raised in monolingual households. To ensure the study measured sustained language exposure, the researchers excluded any child who failed to maintain fluency in all the languages spoken in their respective households throughout the decade. At the end of the study, the bilingual cohort scored significantly higher on cognitive flexibility assessments. Therefore, early exposure to multiple languages enhances cognitive flexibility.

The linguist's reasoning is most vulnerable to criticism on the grounds that it

  1. incorporates a selection criterion for its sample that is likely to favor individuals who possess the very cognitive trait the researchers were investigatingAnswer
  2. B
    relies on an ambiguous shift in the meaning of the term 'fluency' over the course of the argument
  3. C
    infers a causal relationship from a mere correlation without considering that the presumed effect might actually be the cause of the presumed cause
  4. D
    incorporates outside assumptions about the problem-solving opportunities available in monolingual households that are not supported by the text
  5. E
    draws a conclusion about the absolute number of children demonstrating cognitive flexibility based on comparative average scores between the two cohorts

Answer

The correct answer is the option stating that the argument incorporates a selection criterion for its sample that is likely to favor individuals who possess the very cognitive trait the researchers were investigating.
The correct answer accurately identifies the critical sampling flaw in the study's methodology. By establishing a rule that excludes any child who failed to maintain language fluency over a ten-year period, the researchers likely eliminated subjects who inherently possessed lower cognitive flexibility. Because this exclusion disproportionately filters the bilingual group (who had the much harder task of maintaining multiple languages), the final sample is fundamentally skewed. The surviving bilingual cohort consists primarily of children who already had the cognitive tools necessary to maintain multiple languages, rendering the final comparison invalid.

Step-by-Step Solution

1
Identify the conclusion of the argument.
The conclusion is: 'Therefore, early exposure to multiple languages enhances cognitive flexibility.'
Understanding the exact claim being made is necessary to evaluate the evidence provided.
2
Analyze the premises and the methodology used to reach the conclusion.
Researchers tracked two groups over ten years but applied a strict exclusion criterion: they removed any child who failed to maintain fluency in all household languages.
In Logical Reasoning questions involving studies, the methodology often contains the core logical vulnerability.
3
Evaluate the relationship between the methodology and the conclusion to find the logical gap.
Maintaining fluency in multiple languages over a decade is cognitively demanding. Children with lower cognitive flexibility are more likely to drop a language and be excluded. Thus, the final bilingual sample consists primarily of those who inherently possessed high cognitive flexibility to begin with.
This reveals a severe selection bias (survivorship bias). The sample is skewed by the very trait it aims to measure.
4
Match the discovered flaw with the answer choices.
The correct option abstractly describes this methodological flaw by noting the selection criterion favors those who already possess the investigated trait.
The correct answer must accurately and precisely describe the structural weakness in the argument's reasoning.

Key Concept

Selection Bias / Unrepresentative Sample
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Topics

Sampling and Survey Flaws

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