For a difficult inference question based on an experiment, compare the groups across every stage and distinguish partial effects from complete explanations. Favor the cautious option that accounts for all observed results, and reject choices that reverse the evidence, introduce an unsupported cause, or claim that only one factor matters when the results indicate multiple influences.
Hints
- Hint 1
Track behavior across both years
Compare what each group did during its first migration with what it did when traveling without adults the following year.
- Hint 2
Separate route from destination
Consider both the initial path taken by the formerly escorted birds and the wintering area toward which they eventually turned.
- Hint 3
Avoid an all-or-nothing conclusion
Ask whether the second-year behavior can be explained entirely by first-year experience or entirely by population of origin.
Step-by-step
- Step 1
Compare the first migrations
The juveniles that traveled with eastern adults followed the eastern route, while those that traveled without adults used the western population's usual route. This difference indicates that adult companions affected the juveniles' initial route choices.
- Step 2
Analyze the second-year behavior
When migrating alone the next year, the formerly escorted juveniles began along the eastern route. That repeated behavior shows that their experience with the eastern adults had a lasting influence rather than affecting them only while the adults were present.
- Step 3
Account for the change at the fork
The formerly escorted juveniles did not repeat the complete eastern migration: they eventually turned toward the western population's usual wintering area. The evidence therefore supports a combination of lasting social influence and influences associated with population of origin, making the first option the best-supported completion.