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Difficulty: MediumAssumptions in Causal Arguments

Researchers recently observed that office workers who regularly consume green tea report experiencing significantly lower levels of daily stress than those who do not. Furthermore, among the workers observed, those who consume the greatest amount of green tea report the lowest stress levels. The researchers conclude that the antioxidants present in green tea act directly on the nervous system to reduce stress.

Which one of the following is an assumption on which the researchers' argument depends?

  1. An office worker's level of daily stress does not dictate their likelihood of consuming green tea.Answer
  2. B
    Consuming beverages that contain antioxidants is sufficient to noticeably reduce an office worker's daily stress levels.
  3. C
    If the office workers in the study were to stop consuming green tea, their reported stress levels would immediately increase.
  4. D
    Green tea contains a significantly higher concentration of antioxidants than any other beverage commonly consumed by the surveyed workers.
  5. E
    The office workers who do not consume green tea generally consume beverages that actively increase nervous system stress.

Answer

The argument depends on the assumption that an office worker's level of daily stress does not dictate their likelihood of consuming green tea (ruling out reverse causation).
The correct answer rules out the possibility of reverse causation. The argument observes a correlation between green tea and lower stress, and concludes that the tea causes the lower stress. For this causal claim to be valid, it must be true that the causal arrow does not point the other way. If it were true that having low stress naturally leads people to drink green tea, the conclusion would fall apart. Therefore, the argument implicitly assumes that an individual's stress level is not what dictates their tea consumption.

Step-by-Step Solution

1
Analyze the argument's structure to identify the premises and conclusion.
Premise: There is a dose-dependent correlation between green tea consumption and lower stress. Conclusion: Antioxidants in green tea directly reduce stress.
Deconstructing the argument is the first step in identifying the logical gap.
2
Identify the logical gap between the premises and the conclusion.
The premises only establish a correlation, but the conclusion claims a specific causal relationship (A causes B).
Causal conclusions drawn from correlational data always contain logical gaps, as there are alternative explanations for the correlation.
3
Determine what type of assumption is needed to bridge this gap.
A necessary assumption is required. This often takes the form of a 'Defender' assumption that rules out an alternate cause or reverse causation.
The question stem asks for an assumption the argument 'depends' on.
4
Evaluate the options using the Negation Test.
Negating the correct option yields: 'An office worker's level of daily stress DOES dictate their likelihood of consuming green tea.' If low stress causes people to drink tea, the conclusion that tea causes low stress is undermined.
The Negation Test is the definitive way to prove a necessary assumption. If the negated option destroys the argument, it is the correct answer.

Key Concept

Ruling out reverse causation in causal arguments
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Topics

Assumptions in Causal Arguments

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