Q18 - Learning how to build a

[tzyc]

I first chose (B) but later I felt it might strengthen the conclusion that experience matters (because it says capacity increases after each trial)...how (B) undermines the conclusion?
I changed to (E) but it may be irrelevant because even up to 25% of them were killed, they can observe the rest of them...

Thank you

[zip]

You were right the first time. If the capacity to lay viable eggs increases with age, then that provides alternative cause for the observation that the breeding success of blackbirds increases as they get older. It does not support the conclusion that nest building is the reason for increased breeding success; it provides another causal explanation.

[WaltGrace1983]

The key to (B) is understanding the term "capacity." In this context, it means ability - kind of like in a physiological context. In other words, (B) says that it is NOT the nesting experience that leads to more success in breeding but RATHER it is the adaptation of their bodies - every time they lay eggs, they get better!

I am not crazy about the wording of the stimulus vs. the wording of the answer choice. "Experience" seems awful close to "capacity" but this is an early PT and perhaps it is a little less clean-cut than it might be today. Either way, I am going to break this down.

Year 2 of breeding was more successful than Year 1; Year 3 was more successful than Year 2
+
This cannot be explained by size and strength
→
It must be explained by their nesting experience

I simply want to show why it is NOT the nesting experience that led to this. Maybe the blackbirds get progressively healthier during their first years of nesting. Either way, I just want to show an alternative explanation as that is basically the best way to weaken this claim.

(A) "Other birds?" Who cares?

(B) Yea! If the ability to lay more viable eggs increases, then it is NOT the nesting experience but rather their physiology that explains the uptick in success: their eggs are more viable!

(C) We basically already knew this: premise booster.

(D) This actually strengthens by ruling out an alternative explanation. It says that strengthen and size don't matter! Thus, we couldn't just say, "well during the 2nd and 3rd years the birds were stronger or bigger!" to weaken this claim because (D) says, "not so fast! Those things don't matter!" Whenever we rule out an alternative explanation, we are strengthening the argument if just by a little.

(E) "All birds" is too wide of a scope and we don't care about happens before they start to nest - we care about what happens after!