Ornithologist: In a behavioral study, captive migratory songbirds placed inside an indoor planetarium failed to orient toward their southward route whenever the artificial night sky was darkened. This demonstrates that these songbirds rely exclusively on celestial patterns rather than geomagnetic fields to determine their migratory direction.
The claim that the planetarium testing room was encased in thick metal shielding that completely blocked Earth's ambient geomagnetic field, if true, weakens the ornithologist's argument.
Answer: Answer
Answer
True. The supplementary statement introduces an alternative explanation that undermines the author's conclusion.
The statement is true because the presence of magnetic shielding invalidates the premise that geomagnetic cues were available as a backup. Because the birds were deprived of all navigation cues when the lights went out, their failure to orient does not demonstrate that they cannot use geomagnetic fields under normal conditions.
Step-by-Step Solution
Key Concept
Weakening a causal conclusion by identifying an unaddressed experimental confound or alternative explanation.