A finding question that weighs two causes tests whether evidence supports one explanation over another. Read the conclusion and put its cause, effect, and rejected cause in a few words. Separate what the claim credits from what it rejects. Then predict a finding that tests both parts: it should link the claimed cause to the effect while ruling out the other cause. Evidence that fits both causes can't show which one matters more, even if it shares the claim's topic.
Hints
- Hint 1
Split the researchers’ conclusion into two parts. What do they credit for the greater number of gobies, and what do they reject?
- Hint 2
Return to the video of gobies retreating into gaps. What might it tell you about how the gobies respond to danger?
- Hint 3
Ask what would separate the two explanations. How could you test the role of the gaps without leaving food availability as another reason for the result?
Step-by-step
Separate safety from food
Step 1Split the conclusion into two parts
The conclusion credits the modules’ crevices reducing perceived predation risk for the higher goby numbers, so the finding needs to link the gaps to a sense of safety. What else must it show? The phrase not from the greater availability of prey adds a second part: extra food isn't the main reason more gobies gathered there.
- Step 2
Predict a test that separates the causes
What would separate these two explanations? The video shows gobies retreated into gaps between shells, which links the gaps to a response to predators, but leaves the food difference in place. Let's predict a stronger test: whether sensing danger changes the gobies’ preference for crevices when food can't explain the difference.
- Step 3
Set aside findings that miss a part
The predator-free laboratory tanks compare shell with ceramic, so they don't show whether crevices caused the preference or connect it to danger. Attacks that are less often successful show protection, but leave extra food as a possible cause of the greater abundance. The same average number of crustaceans shows how many crustaceans gobies ate, not whether crevices changed the gobies’ sense of danger.
- Step 4
Identify what changes the preference
What does the finding with predator odor hold steady, and what changes? The structures differ in crevices, but both are ceramic and have equal prey, so food supply and shell material can't explain the preference. Gobies favor the creviced structure only once they smell a predator, which links the gaps to their sense of danger rather than to a food advantage. Choice B.