Passage Summary: A study found no difference in behavior between kids who ate sugar and kids who ate fake sugar, so the researchers think sugar doesn't cause hyperactivity.

Conclusion: We can stop believing the idea that eating sugar makes children with attention deficit disorder more hyperactive.

Reasoning: A study showed that children with the disorder behaved the same whether they were given real sugar or a sugar substitute.

Analysis: To weaken this argument, we need to find a reason why the study's results might be misleading. The researchers used a 'sugar substitute' as a control, but what if that substitute also causes hyperactivity? If both the experimental group and the control group were bouncing off the walls, the 'no difference' finding wouldn't prove that sugar is harmless. Look for an answer choice that suggests the control group was not a valid baseline for calm behavior.