Match each argument with the fundamental unstated assumption required for its conclusion to be logically justified.
- Cognitive Scientist: Participants who completed intensive navigation training in virtual three-dimensional environments showed a significant increase in posterior hippocampal volume. Because this enlargement occurred only in subjects actively navigating the virtual mazes and not in control subjects who passively watched pre-recorded navigation videos, the neural growth must have been directly stimulated by the cognitive demands of active spatial decision-making rather than the visual immersion of the simulation.The manual motor activity required to operate physical navigation controls during the virtual tasks did not independently cause the observed increase in hippocampal gray matter.
- Urban Economist: To curtail air pollution, city planners propose subsidizing electric cargo bicycles to replace diesel commercial delivery vans. However, replacing diesel vans with electric cargo bikes will fail to decrease aggregate urban particulate emissions, because cargo bikes possess a substantially lower freight capacity per vehicle, necessitating at least four cargo bikes to transport the cargo volume previously moved by a single diesel van.The non-exhaust particulate emissions generated by four electric cargo bikes, such as tire and brake dust, do not amount to less than the total particulate emissions produced by one diesel delivery van.
- Marine Ecologist: Deep-sea sediment cores demonstrate that benthic foraminifera shell density plummeted during a prehistoric warming epoch fifty-five million years ago. Because benthic foraminifera build their shells from dissolved carbonate ions, ocean acidification driven by massive atmospheric carbon release must have been the sole cause of this precipitous decline in shell calcification.Elevated seawater temperatures during the prehistoric warming epoch did not directly impede the physiological calcification process in benthic foraminifera independently of ambient water acidity.
Answer
Argument 1 regarding virtual spatial navigation matches the assumption that manual motor activity did not independently drive hippocampal growth. Argument 2 regarding electric cargo bikes matches the assumption that four cargo bikes do not produce fewer total particulate emissions than one diesel van. Argument 3 regarding benthic foraminifera matches the assumption that elevated ocean temperatures did not independently impede shell calcification.
Each correct pairing links an argument to a premise-to-conclusion gap that is strictly essential. For the cognitive science argument, ruling out manual motor manipulation defends the causal attribution to spatial cognition. For the urban logistics argument, establishing that four electric cargo bikes do not emit less total particulate matter than one diesel van is required to justify why the substitution fails to decrease net pollution. For the marine ecology argument, ruling out direct thermal inhibition is necessary to uphold the claim that acidification was the sole causal factor.
Step-by-Step Solution
Key Concept
Necessary Assumption identification via the Negation Test and alternative explanation defense
Estimated Time:2m 30s