Left-handed persons suffer more frequently than do right-handed person

This question is asking which hypotheses is best supported by the information in the passage. Let's take the answer choices on by one:


We know that "left-handed persons suffer more frequently than do right-handed persons from certain immune disorders." So if you picked a random group of say 100 left-handed people and another random group of 100 right-handed people, you'd expect more of the left-handed people to have immune disorders. But this doesn't mean that most people who suffer from immune disorders are left-handed, as answer choice (A) says.

That's because we don't know the balance of left-handed versus right handed people in general. If the majority of people are right handed, for example, there could still be more right-handed people with immune disorders, even if right-handed people suffer from immune disorders less frequently. Since the hypothesis that most people who suffer from immune disorders are left-handed is not supported by the passage, (A) is out.


Just because left-handed people suffer from immune disorders such as allergies more frequently than do right-handed people, this doesn't mean that most left-handed people have some kind of allergy. If only 1% of right-handed people have an allergy, for example, then the percentage of left-handed people with allergies could be as low as 2% (or 1.000001%) - so definitely not most left-handed people. (B) is out.


The passage tells us that left-handers tend to have an advantage over the right-handers on "tasks controlled by the right hemisphere of the brain." Additionally, we learn that "mathematical reasoning is strongly under the influence of the right hemisphere in most people."

So if mathematical reasoning is largely controlled by the right hemisphere, and if left-handers have an advantage over right-handers on tasks controlled by the right hemisphere in most people, we'd expect that left-handers would generally have an advantage over right-handers when it comes to mathematical reasoning.

Following this logic, if we took a random sample of left-handers and a random sample of right-handers, we'd expect the mathematical ability of the left-handers to be higher in general. And if that were true, more of the left-handers would have above average mathematical abilities than the right-handers. Let's hold on to (C).


The passage makes no connection between left-handed people who suffer from allergies and left-handed people who are good at mathematics. And although we'd expect left-handers to have an advantage over right-handers in terms of mathematical ability, that doesn't tell us whether any particular left-hander is "good at math." Since it's not supported, (D) is out.


The passage doesn't tell us anything about the proportion of people in general who suffer from immune disorders. Nor does it tell us much about what proportion of left-handed people are good at mathematical reasoning -- aside from the fact that the proportion is bigger than it is for right-handers. As a result, we have no basis to compare these two groups of people, and (E) is out.

So we're left with (B).

I hope that helps!