Kaplan Difficult Psych Q

[mynameisno]

If D can be a conclusion based on the study, then why can't A? Since the size of the hippocampus increases with years of experience as a taxi driver, can't that indicate a causal relation? (sorry posted this as well in the general MCAT discussion cause I forgot about this subgroup)

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[smukke]

It isn't a psych question. It's an experimental set up question. It's also a "choose the better answer" question.

Most of the first study is a distracter since the only part that matters is the last sentence, where they tell you that there is a positive correlation between years driving by taxi drivers and hippocampus volume. More taxi driving = larger hippocampus. (Always read the second study first, it's usually the shorter/smaller one with less variables and you'll get less distracted when asked to compare the two; if a variable isn't in study 2 ignore it)

Second study only compares hippocampus volumes and infers taxi drivers are larger than bus drivers, even though they drove similar hours and conditions, only difference is that bus drivers drove a set route.

Therefore on based off the 2 studies, you find when comparing hippocampus volumes taxi > bus = controls (non drivers?). A might be correct, but based on the information given in the passages there's no way to prove it whereas D can be proven since they both drove in similar conditions but didn't have the same effects.

 

[mynameisno]

It isn't a psych question. It's an experimental set up question. It's also a "choose the better answer" question.

Most of the first study is a distracter since the only part that matters is the last sentence, where they tell you that there is a positive correlation between years driving by taxi drivers and hippocampus volume. More taxi driving = larger hippocampus. (Always read the second study first, it's usually the shorter/smaller one with less variables and you'll get less distracted when asked to compare the two; if a variable isn't in study 2 ignore it)

Second study only compares hippocampus volumes and infers taxi drivers are larger than bus drivers, even though they drove similar hours and conditions, only difference is that bus drivers drove a set route.

Therefore on based off the 2 studies, you find when comparing hippocampus volumes taxi > bus = controls (non drivers?). A might be correct, but based on the information given in the passages there's no way to prove it whereas D can be proven since they both drove in similar conditions but didn't have the same effects.

But given that more years driving=larger hippocampal volumes for taxi drivers and what they said in the first paragraph that taxi driving requires a fair amount spatial reasoning, I still don't understand why A can't be right if we know that more years driving=larger hippocampus? Unless it can be inferred that the larger volume is due to some other aspect of driving but that can be ruled out because taxi drivers have larger hippocampal volumes than bus drivers.

 

[PositivePhotoresist]

Remember that correlation does not equal causation. That is why choice A is out. Generally, it is easier to rule out potential causes rather than to prove them 100%.

Causation is definite. Correlation still has some room for uncertainty.

 

[smukke]

But given that more years driving=larger hippocampal volumes for taxi drivers and what they said in the first paragraph that taxi driving requires a fair amount spatial reasoning, I still don't understand why A can't be right if we know that more years driving=larger hippocampus? Unless it can be inferred that the larger volume is due to some other aspect of driving but that can be ruled out because taxi drivers have larger hippocampal volumes than bus drivers.

Like I said, A might be correct but we can't make that conclusion based on just these 2 studies (it's also important to recognize when knowing more than provided is detrimental). But D is more correct.
PositivePhotoresist brings up a good point that it's generally easier to rule out than prove (rule in) and is a good strategy as well when doing these types of compare 2 study questions.