Q23 - A certain species of bird has two basic varieties, cre

[ottoman]

I narrowed it down to choice D and E but had hard time understanding why E is the right answer. Can someone help me with this answer?

Thank you!

[sumukh09]

The conclusion is that the selection of crested or non crested has nothing to do with genetics but rather it is a learned trait. D says that if a crested bird lives alone with no other birds and is later moved to a mixed flock, it chooses a crested bird as a mate. This would weaken the argument that the trait is learned and would strengthen the argument that the trait is genetic. Not what we want.

E) strengthens the idea that the trait is learned. Showing no preference when raised in a mixed flock implies genetics do not influence which kind of bird is selected which makes helps the notion that the trait is learned rather than genetic.

[alexroark5]

The author concludes that the birds' preference for crested vs noncrested is one that is LEARNED, and NOT genetically predetermined.

The evidence offered in support of the conclusion is that birds raised in crested flocks, when moved to a mixed flock with crested and noncrested birds, will select a crested mate, regardless of whether or not the bird who is doing the selecting is crested or not.

It is a simple argument and the first thing that you should notice right away is that the argument ends with a CAUSAL conclusion. So right away your brain should switch to strengthening a causal conclusion mode. There are generally only a few ways to strengthen a causal conclusion:

1. Show that when the cause occurs, the effect occurs
2. Show that when the cause does not occur, the effect does not occur
3. Eliminate any alternate causes for the stated effect
4. Eliminate the possibility that the stated causal relationship is reversed
5. Show that the data used to make the causal conclusion is sound

Answer choice E is the credited response. It functions as method number 2 above (show that when the cause does not occur, the effect does not occur). Being raised in mixed flock is taking away the stated cause (of learning to prefer crested vs noncrested by being a flock of entirely crested birds or vice-vesa) and showing that as a result, the stated effect does not occur (birds do not show a preference for crested vs noncrested).

Answer choice D does the exact opposite of what we want. It strengthens the causal relationship of the argument in favor of crested vs noncrested preference being genetically predetermined. It does this by method #3 above (eliminating a possible alternative cause). It eliminates the possibility that the preference for crested vs noncrested is learned. How could it be learned if the bird is raised in captivity? By eliminating the possibility that preference for crested vs noncrested is learned, it strengthens the causal conclusion that the preference for crested vs noncrested is genetically predetermined.

Hope that helps