Ecologist: One theory attributes the ability of sea butterflies to avoid predation to their appearance, while anothe...

Naz on October 27, 2015

One theory attributed attributes the ability of sea butterflies to avoid predation to their appearance, while another attributes this to various chemical compounds they produce. In order to rule out the second theory, each compound was added to food pellets, ONE COMPOUND PER PELLET. Predators ate the pellets no matter which one of the compounds was present. We conclude from this that the compounds the sea butterflies produce are not responsible for their ability to avoid predation.

What's the issue here? We are not told whether the compounds that the butterflies produce are used individually or together as a group. However, the test to see whether this theory is valid only tests each compound individually. What if, instead, the sea butterflies excrete many different chemicals at once that TOGETHER work to avoid predation. We have a part to whole flaw here where we attribute the fact that each one compound cannot deter predators to the unnecessary conclusion that all the compounds together cannot deter predators.

This is exactly what answer choice (D) points out: "infers, from the claim that no individual member of a set has a certain effect, that the set as a whole does not have that effect."

Answer choice (B) is describing a correlation/causation flaw, which this stimulus does not have. We are looking for a part to whole flaw. There is no correlation given to us in the stimulus. Again, we are using the results of study that tested each compound individually as opposed to together as a whole.

Hope that clears things up! Please let us know if you have any other questions.

wills on March 23, 2019

Can you explain why A is incorrect? Could it not be that the butterflies both release the compound and use their appearance together in order to escape predators. Therefore, the argument would be presuming that the theories are incompatible with each other.

Jacob-R on March 23, 2019

Answer A states that the argument presumes that the two theories (chemical compounds or appearance) are incompatible with each other. What is crucial to recognize, though, is that we are looking for the answer that explains why the ecologist’s argument is flawed. The ecologist’s argument is that the compound theory is not responsible for the ability of butterflies to avoid predation — this argument does not presume incompatibility of the two theories, or compatibility for that matter. It is simply an argument that one of the two theories is not responsible for the observed effect.

I hope that is helpful. Please let us know if you have further questions.

JPB on July 20, 2021

The most difficult aspect of logical reasoning is how questions pivot on one word or maybe a few: from "each" to "one", unless you catch that "one per pellet concept", you are not there. Difficult in that we assume this butterfly test is well structured, when the science test is flawed and we must catch that flaw in the statement.