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Difficulty: MediumWeaken

Chronobiologist: A recent two-year study monitored adolescent students who completed their academic assignments during early morning hours rather than late evening hours. These morning-studying students reported substantially higher sleep quality and improved memory retention. Therefore, shifting mentally demanding tasks from late evening to early morning directly optimizes sleep architecture and cognitive performance in adolescents.

Which of the following statements, if true, most seriously weaken the chronobiologist's argument? (Select all that apply)

  1. Students who voluntarily shifted their study schedule to the morning already adhered to stricter household limits on evening screen exposure, an independent factor known to improve adolescent sleep quality.Answer
  2. B
    Completing intellectually intensive assignments late at night causes sustained elevations in pre-sleep physiological arousal that inhibit restorative slow-wave sleep.
  3. Adolescents with naturally advanced circadian rhythms, who inherently experience superior sleep consolidation and baseline memory retention, are disproportionately more likely to adopt morning study routines.Answer
  4. D
    A portion of the self-reported sleep logs kept by students during the study contained minor recording discrepancies regarding exact bedtimes.
  5. E
    Adult professionals in demanding occupations do not experience measurable improvements in cognitive performance when shifting work hours from evening to morning.

Answer

The statements establishing an alternative confounding cause (household screen time limits) and a self-selection bias based on preexisting biological chronotypes both weaken the argument by undermining the author's direct causal conclusion.
The conclusion asserts a direct causal relationship based purely on a correlation observed between study timing and sleep/memory metrics. The statement showing that morning studiers were subject to stricter evening screen time limits provides an alternative causal explanation for the improved sleep. Similarly, the statement showing that students with naturally advanced circadian rhythms already possess superior sleep consolidation demonstrates that baseline biological differences, rather than the schedule change itself, likely account for the observed benefits.

Step-by-Step Solution

1
Identify the conclusion and underlying premises in the argument.
Premise: Morning-studying adolescents had better sleep quality and memory scores than evening studiers. Conclusion: Shifting mentally demanding tasks to the morning directly causes optimized sleep architecture and cognitive retention.
Weaken questions require targeting the unstated logical gap between the correlation observed in the premise and the causal link asserted in the conclusion.
2
Formulate potential vulnerabilities in the causal inference.
The author assumes no confounding third variables (such as other lifestyle habits) and no self-selection bias (inherent physiological differences between morning and evening types) explain the observed correlation.
Causal claims based on observational studies are inherently vulnerable to alternate causes, reverse causality, and selection bias.
3
Evaluate each choice against the causal gap.
The option citing stricter household screen limits introduces a plausible confounding variable, and the option noting inherent circadian advantages explains the correlation via selection bias. Both undermine the conclusion.
Introducing credible alternative explanations directly breaks the necessary assumption that the homework timing itself caused the beneficial outcomes.

Key Concept

Alternative Causal Explanations and Selection Bias
Estimated Time:1m 30s
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