Researcher: We studied two groups of subjects over a period of six months. Over this period, one of the groups had a...

shunhe on February 1, 2020

Hi @Stephanie,

Thanks for the question! This is a “Must Be True” question. We need to find a statement supposed by those in the stimulus. What does the stimulus tell us? Essentially, a study was done, and it showed that people who exercised in the afternoon got more deep sleep than people who didn’t. Why? Because this exercise raised body temperature slightly until after bedtime, which induced deeper sleep. Now let’s go through the answer choices.

(A) is wrong because there is no mention of whether or not either group’s deep-sleep is “adequate.” Both could be, neither could, one could be and one couldn’t be. We also don’t know that regular afternoon exercise is REQUIRED for adequate deep sleep; it could just be one of many ways that can lead to it.

(B) is wrong because there’s nothing suggesting that morning exercises will have as many beneficial effects on sleep as afternoon exercise. We might actually think the opposite, since the body temperature is only raised until slightly after bedtime, so exercising way earlier would mean that body temperature lowers back to normal by bedtime, which might mean that the deep-sleep benefits won’t be as pronounced, if they’re there at all.

(C) is wrong because we don’t know if this slight increase in body temperature is the BEST way to get increased deep-sleep. Maybe the more we increase body temperature, the more deep-sleep there is. Either way, the stimulus is silent on this issue.

(D) is wrong because we aren’t told that NO ONE in the control group experienced this rise in body temperature. There could have been one person who did, or a few people who did but to a lesser extent than those who exercised. But nothing in the stimulus rules out the possibility of people in the control group having a higher body temperature just before bedtime.

(E) is the correct answer, as it sets up a situation analogous to the one set up in the stimulus. Though the mechanism is different (warm baths instead of exercising in the afternoon), the result is still a raise in body temperature around when people sleep, and it is this factor that was identified as inducing longer periods of deep-sleep.

Hope this helps! Please feel free to ask any further questions that you might have.