Researchers asked 100 fifty-year-olds and 100 twenty-year- olds whether they gave blood.
Conclusion
There is reason for skepticism about the conclusion that
Evidence
Many people hesitate to admit that their behavior does not conform to social expectations.
Evaluate
There was a study with a Curious Fact (an asymmetric comparison): why is it that twice as many 50 year olds as 20 year olds reported that they sometimes give blood?
The researchers concluded one potential Explanation: 50 year olds are more altruistic than 20 year olds (obviously assuming that being more altruistic is causing them to be more likely to give blood).
This author is pushing back against that conclusion by suggesting an Alternate Explanation:
Goal
We're being asked how our author is calling into question the researchers' conclusion. We'll take any answer that seems descriptively true, but we'd probably anticipate language like, .