Self-study
Support A local chemical plant produces pesticides that can cause sterility in small mammals such as otters. ████ █████ ███ █████ █████ ██████████ ███ █████████ ██ █████████ █████ ███ ██████ ████ ████ ██ █ ██████ █████ █████████ █████████████ ██████████ ██████████ ███ ██████████ █████████████ ███ ██████
Method of Reasoning
The author concludes that pesticides have contaminated the river. His reasoning is that, after a factory opened, there was an increase in sterility among rivers otters. The pesticides produced by the factory can cause sterility in animals like otters.
Identify and Describe Flaw
The author identifies a causal connection between the plant and the increased sterility, but his reasoning is flawed on two counts. Firstly, we don’t know that the pesticides produced by the plant ever reached the river. So we don’t know if the suggested cause in fact occurred.
Secondly, we don’t know that the only possible cause of an increase in sterility is exposure to pesticides. If there are other possible causes, an increase doesn’t necessarily suggest that pesticides are at fault.
11.
Which one of the following █████████ ████████ █ ████ ██ █████████ ████ ██ ███████ ██ ███ ██ ███ ████████ ██████
a
The bacteria that █████ ███████ ████ ██ ███ █████████ █████ ██ ███████ ███████ ██ █ ██████ ██████████ ████████ ████████████ ██ ████ ██ ████ ██████ ████████ ███████ ████ ██████████ ████ ██ ████ █████ ████████
This is not a matching flaw. (A) is flawed because we have no knowledge of how comparatively frequent tetanus infections are for horses as opposed to other animals. By contrast, the stimulus is flawed because it assumes, without adequate evidence, that a causal connection between the plant and otters’ sterility exists.
b
A diet low ██ ███████ ███ █████ █ ████ ██ ███ ██████████ ██ ████████ ████ ████████ ██ █ █████ ████ ████ ███ ███ ██ ███ ██████ ██ ██████ ███ █████ █████ ███ ██████████ ███████ ███████████ ██ ███ ████ █████ ███ █████ ██ ███ ████████ ██ ██████████ ███ ██ ████████
(B) concludes that the chickens foraged food with low calcium. The reasoning is that, after they foraged, they laid fewer eggs. And reduced calcium can cause a decrease in egg production.
Like the stimulus, this argument is flawed on two counts. Firstly, it assumes, without justification, that the proposed cause (the foraged diet was low in calcium) did in fact occur. Secondly, it assumes that this is the only possible cause for the observed effect (fewer eggs laid).
c
Animals that are ██████████████ ███ ████ ███████████ ██ ██████████ ███████ ██ ███ ███████ ████████████ ████ ███ ███ ███████████████ ██ ████ ██████ ████ ███ ██ ████ ███████████ ██ ████████
This is the wrong flaw. (C) is based on a conditional statement: if undernourished, an animal is susceptible to infection. It negates both sides of the statement, and erroneously assumes that the statement remains valid. (Even if hungry animals are sickly, well fed animals might also be sickly.) By contrast, the stimulus made two unwarranted assumptions to establish a causal relationship.
d
Apes are defined ██ ███████ █████ █████ ████████████████ █████████ ██████ ███ ██ ████████ █████ █████████ ██████ ███████ ██ █ ██████████ ███████ ██████ ████ ██████ ███████ ████ ██████ ███ █████████ ███████ ██ ████ ████ ████ ██ ████
This is the wrong flaw. (D) commits the cookie-cutter flaw of confusing sufficiency and necessity. All apes have opposable thumbs, but that doesn’t mean all animals with opposable thumbs are apes. By contrast, the stimulus made two unwarranted assumptions to establish a causal relationship.
e
The only animal ████ █████ ████ ████████ █ █████ ███████ ██ ████ ███ ██ █ █████ ███ █████ ███ ██ █████ ██ ████ ████ ██ ███ ████████ ██ ████ ██████ █████ ██ █ █████
This argument is not clearly flawed, and doesn’t parallel the stimulus. (E) concludes that a cause (a bear) couldn’t have led to an observed effect (tracks). By contrast, the stimulus unwarrantedly concludes that a cause (pesticides from the plant) must have led to an effect (otter sterility).