Comment by djsumdog | Hacker News Reader

Comment by djsumdog | Hacker News Reader

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There are a lot of worthless measures we use out there. Body Mass Index (BMI) is another one. This scale was developed in the mid 1800s and you can do a simple search to find tons of criticism on it. If you're overweight/obese, you will have a high BMI, but not everyone with high BMI is overweight (especially if you're very tall or very short).

Measuring Cholesterol is another one, since you can't actually change cholesterol via diet and it has no relation to heart disease either (source: http://www.health.harvard.edu/blog/panel-suggests-stop-warni... ). But the pharmaceutical industry still wants doctors to prescribe Statins and pours tons of money into advertising them to people and doctors, even though they're terrible for you and worthless.

It's troubling when industry grasps onto these measures and makes business models out of them. Wide spread acceptance of measures like these moves them out of the realm of homeopathy or astrology and into the realm of what people believe as relevant scientific measure. They benefit industry, but not the individual. Advertising allows that industry to continue to grow at the expense of good relevant data.

Invisibilia ran a great episode on "the personality myth"[1] and I think it shows the difference between BMI and "personality tests". BMI might be worthless but it measures something that objectively exists. Is it useful? Maybe not. Personality tests measure something that we don't even know exists, personality.

The episode talks about research showing how we can understand ourselves better as sets of behavior that we exhibit in different contexts, more than as having a single personality.

Put in simple words, you maybe introvert in some contexts and extrovert in others, and theses behaviors can change over time. You ARE not AN introvert, you exhibit introvert behaviors in context.

[1]: http://www.npr.org/programs/invisibilia/482836315/the-person...

> Personality tests measure something that we don't even know exists, personality.

This sentence strikes me as odd, because subjectively, the one thing that shines through the most with people, even people I haven't seen in 20+ years, is a distinct (and possibly largely immutable) personality. In fact, a large part of why I was so shy growing up is because people's personalities were so "bright" that I felt intimidated. Not of course "bright" in a literal, measurable sense, but in an irrational qualitative sense. And therein lies the problem with trying to discuss it rationally.

To this day I perceive distinct personalities in every child and pet I encounter. Not sure if related, these exact same entities seem drawn to me for some reason. I have often heard a pet owner say "my pet has never acted this way before" around me (such as sitting in my lap when it has never done so with anyone).

I wonder if it simply reflects what I see in them. Anyway. My point is that the inability to discuss something rationally is not evidence for its nonexistence.

They never claimed evidence of nonexistence.

They claimed there's simply an absence of unambiguous evidence that it exists.

Thank you for the clarification.

My argument is then that we will never have evidence that it exists because evidence is rational and objective and its very reality and/or value is trapped in the irrational subjective eye of the beholder.

Trying to boil it down into, say, patterns of neuron activations would be like trying to boil down or derive the "value reality" of the Mona Lisa by analyzing and cataloguing the light wavelengths reflecting off of it.

The claim that we will never have evidence that it exists says more about your need to not have your belief in its existence questioned than it does about the actual likelihood of evidence being found in the affirmative or negative.

Everything we know about what "evidence" is, is measurable.

So what of the unmeasurables?

I have no idea what you're responding to now.

> There are a lot of worthless measures we use out there. Body Mass Index (BMI) is another one. This scale was developed in the mid 1800s and you can do a simple search to find tons of criticism on it. If you're overweight/obese, you will have a high BMI, but not everyone with high BMI is overweight (especially if you're very tall or very short).

The metric system was developed in the 1800s and you can do a simple search to find tons of criticism on it.

Being tall or short is accounted for by BMI, as it's a component of BMI. So that is not a problem.

The actual problem with BMI is that it attempts to measure body composition, but it assumes that fat is the only variable component of body composition. It's not--muscle can also vary. So people with a lot of muscle mass can have a very high BMI even if they have very little fat.

However, in practice this isn't a problem--nobody looks at a body builder and says they're fat because they have a high BMI. It's obvious when a high BMI is caused by fat and when it's caused by muscle.

BMI is a pragmatic way to measure body composition, which is effective for estimating body composition when body composition isn't obvious, such as in the case of a body builder. Anyone who tells you otherwise is either misinformed, or has political reasons for saying otherwise.

This is not to disagree with your overall point--industry does grasp into measurements and make business models out of them. But in the case of BMI, political interests have become invested in discrediting the BMI measurement, not in overcrediting it.

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