Which one of the following is most analogous to the manner in which fMRI scans of brain activity are typically interp...

JeremyG on May 25, 2019

Could you please explain why D is incorrect?

I understand why B is the correct answer, but could you please walk me through why D is an invalid answer choice? Thank you.

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Victoria on May 25, 2019

Hello @JeremyG,

The passage tells us that fMRI scans are typically interpreted by subtracting the baseline measurement of metabolic activity from the on-task measurement. The remaining areas of the brain that are lit up by the fMRI are interpreted to be those that are associated solely with the cognitive task in question.

B is the correct answer as it 'subtracts' the increase in summer shoppers from the yearlong advertising campaign and uses this information to conclude that the summer shoppers were the only shoppers that were affected by the yearlong campaign as they were the only ones remaining following this 'subtraction.'

D is incorrect because it is based on an assumption made using information that we are not provided with. We cannot 'subtract' office Internet use from home Internet use or vice versa and we are not provided with an overall picture of Internet use throughout the day. In addition, the fMRI interpretation concludes that what remains is only associated with the task whereas answer choice D concludes that most of the Internet traffic comes from homes rather than the Internet traffic only coming from homes.

Hope this is helpful! Please let us know if you have any further questions.

JeremyG on May 25, 2019

That clears it up, thanks!

medasmx@protonmail.com on September 27, 2021

to me A looks better than B

Ravi on February 7, 2022

@medasmx@protonmail.com, A is tempting, but it doesn't work because it acknowledges the fact a that this study involves a subtraction. If we are looking at an unusually large margin, that means that we're taking into consideration a baseline of sorts. This is precisely what the standard interpretation of brain scans fails to take into consideration, so that's why A isn't parallel.

With B, we're looking for something that implies a misinterpretation because of a failure to look at all of the different nuances of a study. B looks great, as just because the store only saw an increase in shoppers in the summer does not mean that the ads only affected shopper summers. It's possible that everyone was affected, but the number of shoppers only increased in the summer. This is very similar to how certain areas of the brain lighting up after a cognitive activity does not mean that only those areas were activated. It's possible that the whole brain was activiated, but only the lit up areas saw a difference in activation levels. Thus, B is correct.

Ravi on February 7, 2022

Activated* (typo in the last line of my response; sorry about that)