Logical Reasoning

PT110 · S2 · Q17 Dietary researcher: A recent study

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Dietary researcher: A recent study reports that laboratory animals that were fed reduced-calorie diets lived longer than laboratory animals whose caloric intake was not reduced.

Conclusion

The conclusion that North Americans' life spans can be extended by reduced-calorie diets is not supported.

Evidence

Laboratory animals fed reduced-calorie diets lived longer than those not on such diets.

Laboratory animals tend to eat much more than animals in their natural habitats, leading to shorter life expectancies.

Restricting their diets brings their caloric intake back to natural, optimal levels and reinstates their normal life spans.

Evaluate

The argument proposes that the extended life span observed in laboratory animals on reduced-calorie diets merely reflects a return to their natural life span. The author concludes that this cannot extend North Americans' life spans, because the scenario for humans is different from that of laboratory animals. To weaken the argument, we need to suggest that the reduction in calorie intake could still lead to increased longevity for humans, regardless of the context in which laboratory animals eat more than their natural levels.

Goal

Let's find an answer that suggests reduced calorie intake in humans could still result in increased longevity, undermining the dietary researcher's argument that this effect is unique to laboratory conditions.

17.

Which one of the following, if true, would most weaken the dietary researcher's argument?

  1. Correct

    North Americans, on average, consume

    Why this is right

    The author's argument is assuming a difference between lab animals and the average North American: the lab animals are overeating, which is why reducing their caloric intake brings them down to a normal level that extends their life span. But reducing caloric intake for North Americans won't extend their life span, because they aren't overeating (<-- that's the assumption) This answer blows up that assumption. If North Americans are also generally eating too much, then reducing our caloric intake could bring us down to a normal level and potentially extend our longevity, just as it did with lab animals.

    Skill tested: Weaken · how this choice captures the argument's function is the move to repeat next time.

    65% picked this

  2. North Americans with high-fat, low-calorie

    No Impact

    This statement makes it seem like reducing fat might extend life expectancy, but this argument is about whether reducing calories would extend life expectancy (both groups being compared in this answer are on low-calorie diets).

    9% picked this

  3. Not all scientific results that

    No Impact

    This is an incredibly weak statement, so it's unlikely to be a correct answer on Str / Wkn / Pdx. It says "at least one scientific result with important implications for human health was not based on studies of lab animals". Cool. That doesn't tell us anything about calories / North Americans / life expectancy, etc.

    11% picked this

  4. Some North Americans who follow

    Too Weak: some

    This says there is at least one North American who follows a reduced calorie diet and has a long life span. While that does go in our desired direction of arguing that "reducing calories for the average North American could extend life spans", it is but one data point. It doesn't have as strong an effect as (A), which is telling us that "most North Americans are currently consuming more calories than is optimal" .

    10% picked this

  5. There is a strong correlation

    Unclear Impact

    This says that for at least one species of animal, there's a strong correlation between diet and longevity. Diet is a broad term that encompasses the types of food one eats. This argument is more about the quantity than the type. It's about how many calories one eats. So we have no idea how this answer specifically relates to caloric intake. If one person got 2000 calories a day from fruits, vegetables, and protein and another person got 2000 calories from candy, they would have the same caloric intake, but very different diets. The former diet might be strongly correlated with longer lifespan, but that would have nothing to do with caloric intake.

    4% picked this

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