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In Idiocracy, they show an average IQ chart that is declining over the next few centuries. Now, anyone who's studied IQ knows that's nonsense. The average IQ of a population is by definition 100. So, is this merely an instance of inadequate research by the writers, or is there an actual meaning to that chart?

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Just assume that they are comparing the IQ average over time against the average at its maximum point in human history. The same way people compare money over time by correcting for inflation. –  Zoredache Jan 16 at 17:14
    
I would think that it's more like they aren't even comparing them it's just a statistic that shows the average IQ of the population at a starting point X and showing how the average IQ of that population declined over the years, much like the graph I provided in my answer. –  DoctorWho22 Jan 16 at 18:42
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100 is the median IQ of the norming sample group, by definition. If you don't update the sample group, you would be comparing to a fixed population in a fixed point in time. Doing it that way you can very well have declining IQ and that would be what I think the movie was about. That would be a way to visualize that the population is getting dumber. –  eis Jan 16 at 19:37
    
Average (mean, not median) is something like 110 or 120 now, isn't it? –  Izkata Jan 16 at 22:36
    
The Flynn effect seems relevant. Many people, including myself, are very surprised that the "raw" scores on IQ tests are actually trending up. –  David Cary Jan 18 at 4:29

4 Answers 4

It's a comedy.

A joke.

Don't think too hard about a future where populations basically use a Gatorade-equivalent to water plants. It's merely a representation that people are stupid.

Even following internal logic, they'd be stupid enough to forget to (or even how to) calculate accurate median or general averages.

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The smart people would know that the average IQ of the population would decline... It's literally just a chart showing the combined IQs of the people in the country divided by the number of people, if the average is declining that means that a majority of the people's IQ is getting lower.. –  DoctorWho22 Jan 16 at 15:27
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So you're differentiating between the median and the mean? Everyone could be geniuses, and have an average IQ of 50 then (e.g. if 50% of people are all the same smart and everyone else is at around 0) however it cannot get lower than 50 then. –  ike Jan 16 at 15:30
    
Go into a median calculator... Use a sample of the IQs of people in Idiocracy with low IQs... Use a sample size of let's say 10. If 6 people have IQs of 50, 2 of 60, 1 of 70, and 1 of 100... The median is 50. –  DoctorWho22 Jan 16 at 15:39
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THIS JUST IN: "Guy who made Beavis and Butthead may have made a comedy movie not 100% scientifically sound. We now return you to insanity." –  Meat Trademark Jan 16 at 15:44
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"If you're wondering how he eats and breathes and other science facts (la la la), then repeat to yourself, "It's just a show, I should really just relax for M̶y̶s̶t̶e̶r̶y̶ ̶S̶c̶i̶e̶n̶c̶e̶ ̶T̶h̶e̶a̶t̶e̶r̶ ̶3̶0̶0̶0̶! IDIOCRACY" –  Meat Trademark Jan 16 at 16:13

That's one of the key differences between a scientific paper (where exactly correct use of scientific terms and concepts are important) and a work of art (which has no such restrictions).

The main theme of the movie is "What would happen if humans were gradually becoming less intelligent?" (the use of 'what...if' being a common meme in science fiction). How is this concept going to be conveyed to the audience? A graph shows a decline in some measure of intelligence. Is it scientifically accurate or correct? Perhaps not. Is it effective in conveying an important concept to the audience? Yes.

On the other hand, one could argue that the population over which the median is being calculated is every person who every lived and not just every person who is alive now. In that case, the average IQ of those who are alive now could be gradually declining.

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No, either way the median would be 100. –  ike Jan 16 at 15:25
    
The median of the entire population (all people who ever lived) is a constant 100. The median of a subsample (people currently living) could be less. –  Donald.McLean Jan 16 at 15:26
    
Exactly if you take the median from the current population in IQ after the time jump then it would be less than 100... –  DoctorWho22 Jan 16 at 15:31
    
@DoctorWho22 They can't be doing that because the questions have changed. –  ike Jan 17 at 11:58
    
That has nothing to do with recording a new median given the IQs of the current population in the movie... You are stuck on the notion that just because the raw median score for our current IQ tests is 100, that the average IQ of the world is actually 100... The median raw score of 100 will stay that way if they use our methods of testing IQs... I can't stress enough that they are using a chart in the movie that depicts the decline of the average IQ of the human population "as time progresses" aka from starting point A.... to Ending point B (Centuries) in the future. –  DoctorWho22 Jan 17 at 16:03

Actually, you're thinking of IQ Tests representing the median raw score as 100 as an average like in the Wechsler Intelligence Scales.

As stated in the IQ Classification Wiki:

The Wechsler intelligence scales were originally developed from earlier intelligence scales by David Wechsler. The first Wechsler test published was the Wechsler-Bellevue Scale in 1939. The Wechsler IQ tests for children and for adults are the most frequently used individual IQ tests in the English-speaking world and in their translated versions are perhaps the most widely used IQ tests worldwide. The Wechsler tests have long been regarded as the "gold standard" in IQ testing. The Wechsler Adult Intelligence Scale—Fourth Edition (WAIS–IV) was published in 2008 by Psychological Corporation. The Wechsler Intelligence Scale for Children—Fourth Edition (WISC–IV) was published in 2003 by Psychological Corporation, and the Wechsler Preschool and Primary Scale of Intelligence—Fourth Edition (WPPSI–IV) was published in 2012 by Psychological Corporation. Like all current IQ tests, the Wechsler tests report a "deviation IQ" as the standard score for the full-scale IQ, with the norming sample median raw score defined as IQ 100 and a score one standard deviation higher defined as IQ 115 (and one deviation lower defined as IQ 85).

When they say that the average IQ of the population declined they are representing that the median score of the entire population was declining.

There is a website that shows the countries with the lowest average IQ of a population here

http://www.statisticbrain.com/countries-with-the-highest-lowest-average-iq/

For example

Equatorial Guinea's population has an average IQ of 59, while Ethopia has one of 63, which is well below 100.

Here's a real life chart too from

http://www.w-uh.com/posts/030831-IQ_and_populations.html

It states

As you can see, in a 100 year period the world's average IQ will have dropped from 92 to 86, a change of 6%. That is pretty darn significant. And all because of differential population growth.

enter image description here

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But the median score by definition is 100 –  ike Jan 16 at 15:17
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It's only 100 by definition using the common IQ tests that we have currently... If a country is slowly getting dumber and the people are getting really dumb then do you really want to be called stupid? Not that I think they'd care but they'd probably change the IQ standards in that said country to begin with. –  DoctorWho22 Jan 16 at 15:22
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In Idiocracy they would score less than 100. You do realize it's a comedy and satire on declining educational standards, right? It's not a fracking documentary (yet). –  Meat Trademark Jan 16 at 15:30
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The world's average IQ isn't exactly 100... As I stated the median sample raw score is defined by an arbitrary number... It doesn't mean that the world's average IQ is exactly 100... –  DoctorWho22 Jan 16 at 21:24
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If you were to take all the IQs of the entire world and then divide that by the population I can guarantee you that it will not be 100... It might actually be a few off the only reason they use 100 as the number is to make calculations easier for standard deviations... For instance if you take the first 24 of the list from countries with highest iq... you'll get an average of 100.8 but if you take the top 10 lowest IQ from the same list the average is about 66.5 That's a very large gap... –  DoctorWho22 Jan 16 at 21:39

As the original question says, IQ scores are by definition normalized to have mean 100. Interestingly, if you don't renormalize but grade current students by old standards, IQ scores appear to be rising. This is known as the Flynn effect.

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And reversing it, in Idiocracy, they probably never did re-normalize it. Hence, dropping. –  Izkata Jan 16 at 22:43
    
@Izkata They must have re-normalized it, otherwise they would have the same questions as our test. –  ike Jan 17 at 11:53

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