LSAT 142 | Section 4 | Logical Reasoning: Q18

LR Question 18 Explanation

QUESTION TEXT: Pharmacist: A large study of people aged 65-81…

QUESTION TYPE: Flawed Reasoning

CONCLUSION: It’s true that older people’s pineal glands produces less melatonin.

REASONING: People aged 65-81 who take melatonin have less insomnia. Melatonin helps you sleep.

ANALYSIS: This argument has two major flaws. First, this is a classic example of a false comparison. The argument didn’t tell us anything about people who are younger than 65!

If melatonin also helps young people sleep, then we can’t say that older people produce less melatonin. Maybe melatonin deficiencies are common in all ages.

The second flaw is a biased sample. The study only looked at older people who already have insomnia. We don’t know anything about older people who sleep well. Maybe most people aged 65-81 have more than enough melatonin and supplementation wouldn’t help them sleep.

By the way, melatonin disruption is a serious issue. The bright blue lights of our computers and phones late at night prevent melatonin production. You can reduce this issue by installing f.lux on your computer. On Android, use Twilight. On iPhone, you can use Night Shift.

• Flux: https://justgetflux.com/
• Android: https://play.google.com/store/apps/details?id=com.urbandroid.lux&hl=en

Thank me later. On iPhone you can use Night Shift instead, in the settings. This is also available on Mac.

___________

1. This didn’t happen.
   Example of flaw: You spilled water on your computer, and it broke. Therefore, you intended to break your computer.
2. This didn’t happen. It’s true that melatonin manufacturers made a claim, but the argument didn’t use evidence from the melatonin manufacturers to support the claim.
   Example of flaw: Melatonin manufacturers have produced a study that says we should take melatonin. Therefore we should take melatonin.
3. This didn’t happen.
   Example of flaw: Melatonin plays a role in our biological clock. So melatonin must affect that mechanical grandfather clock in the hallway.
4. This didn’t happen.
   Example of flaw: He won the lottery, and he’s happy now. So happiness must lead to lottery victories. If I am happy, I’ll win.
5. CORRECT. The study only looked at older people who have insomnia. It makes sense that people with insomnia have less melatonin. But we don’t know if most people who are aged 65-81 have low melatonin production. Maybe melatonin has little to no effect for most people of that age.