Juvenile monkeys that are separated from their mothers will often show self-destructive behavior, such as picking at their fur or refusing to eat. These behaviors are the most prevalent in monkeys that are caged alone, are somewhat less prevalent when the monkeys are caged with other, unrelated juveniles and adult males, and are the least prevalent, but still observable, when the monkeys are caged with a mixed-gender group of unrelated, adult monkeys.

Which of the following hypotheses best explains the phenomenon described above?
a. The presence of unrelated juvenile and adult male monkeys causes more self-destructive behavior in juvenile monkeys than does the presence of a mixed-gender group of unrelated adult monkeys.
b. The presence of unrelated adult female monkeys is more important to juvenile monkeys in alleviating distress caused by being separated from their mothers than is the presence of unrelated juvenile monkeys.
c. The presence of unrelated adult male monkeys is threatening to juvenile monkeys, causing self-destructive behavior similar to that caused by the separation of juvenile monkeys from their mothers.
d. The presence of unrelated adult female monkeys serves as a suitable substitute for a juvenile monkey’s mother following a separation from the mother.
e. Juvenile monkeys that display self-destructive behavior will engage in this behavior the least when reunited with their mothers, and will engage in this behavior slightly more when caged with adult female monkeys who are not their mothers.

i chose d, because it says that the presence of unrelated adult females serves as a suitable substitute, while i think that b is very strong in saying that the presence of unrelated adult female monkeys is important.

can an instructor please help me understand?

_________________
Ashish
Share not just why the right answer is right, but also why the wrong answers are not.

Ashish,
Sure, let's examine what is going on here. When juvenile monkeys are separated from their mothers, they show self-destructive behavior.

1) The behavior is the worst when monkeys are caged alone.
2) It still exists but is not quite as bad when monkeys are caged with other unrelated juvenile monkeys and adult males.
3) It still exists but is even less prevalent when monkeys are caged with other unrelated adult male and female monkeys. ("These behaviors are . . . the least prevalent, but still observable, when the monkeys are caged with a mixed-gender group of unrelated, adult monkeys")

So which answer choice best explains the result? Let's compare:
B-The presence of unrelated adult female monkeys is more important to juvenile monkeys in alleviating distress caused by being separated from their mothers than is the presence of unrelated juvenile monkeys.
YES. Compare 2 to 3. The monkeys had fewer signs of distress when with the adult male and females than with the juvenile and male monkeys.

D-The presence of unrelated adult female monkeys serves as a suitable substitute for a juvenile monkey’s mother following a separation from the mother.
NOT AS GOOD. The distress behaviors still continue in the presence of the unrelated adult female monkeys, so it's harder to say that they are a "suitable substitute".

Hope this helps!

_________________
Jamie Nelson
ManhattanGMAT Instructor

Jamie, B and D are quite subtle. now that you mentioned the choices, i paid closer attention to the bolded words:

(B)The presence of unrelated adult female monkeys is more important to juvenile monkeys in alleviating distress caused by being separated from their mothers than is the presence of unrelated juvenile monkeys.

i re-read this as the presence of X is more important to Y than is Z
i still contend that this is somewhat convoluted, and could be better said as X is more effective in alleviating Y's stress than is Z.
i feel that the word important is confusing than saying effective, soothing or relaxing.

(D)The presence of unrelated adult female monkeys serves as a suitable substitute for a juvenile monkey’s mother following a separation from the mother.

so this is wrong, because it says adult females can act as juvenile males' mothers -- an absolute replacement.

thanks!

_________________
Ashish
Share not just why the right answer is right, but also why the wrong answers are not.

Exactly ashish, very good work!

_________________
Jamie Nelson
ManhattanGMAT Instructor

Can someone please explain that why is A wrong?

A says: The presence of unrelated juvenile and adult male monkeys causes more self-destructive behavior in juvenile monkeys than does the presence of a mixed-gender group of unrelated adult monkeys.

The whole passage is about the behavior of juvenile monkeys when separated from their mothers. That is a very important distinction. A is saying that juvenile monkeys being with one group causes more self-destructive behavior than when they are in the other group--but is that true if the mother is also in the cage with the juvenile? The mother's absence is critical in having this effect and must be mentioned in the correct answer choice.

_________________
Jamie Nelson
ManhattanGMAT Instructor