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Old 11-07-2018, 08:13 PM
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Is there a normal distribution of intelligence among bears?


If so, how is it made manifest?
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Old 11-07-2018, 08:38 PM
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There's a distribution of intelligence in pretty much every mammal species. Why are you asking, specifically?

Except maybe koalas. They're exceptionally stupid as a rule.
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Old 11-07-2018, 08:38 PM
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If so, how is it made manifest?
Well, there have been incredibly smart bears like Yellow-Yellow who managed to figure out how to open food canisters designed to stop bears, and taught the methods to her offspring. No other bears figured it out, so she was an outlier.

Intelligence is hard enough to measure in humans, so any measurements for bears are going to based on a few simple tasks, like problem solving.
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Old 11-07-2018, 08:53 PM
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If so, how is it made manifest?
The manifestation is that some bears are dumber than the average bear, and some bears are smarter than the average bear.
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Old 11-07-2018, 08:57 PM
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Old 11-07-2018, 09:53 PM
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Those food canisters are a good bit better than Yogi's pic-a-nic basket. Wow, smart bear.
I agree with the fact that any mammal can be just dumb. I have a developmentally delayed Yorkie sitting on my lap staring at her foot, trying to figure out what it is.
I assume a lack of oxygen at birth or an injury could account for some animals having differing levels of intelligence.
Take the pig. They are considered pretty smart creatures. We have a colony of feral hogs roaming close to us and I've seen them do some dumb crap. We had an electric fence around my vegetable garden to keep the hogs out, the dummies would bite at it, getting shocked repeatedly. I couldn't stand it. I bought corn and sprinkled it around my patch and commented how dumb they were. Mr.Wrekker said they were pretty smart to get me to go buy and serve their favorite food. Hmmm!?!?

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Old 11-08-2018, 08:09 AM
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I once saw an intelligence test for dogs, consisting of a set of tasks that some dogs could figure out, but others couldn't. I imagine that a similar test could be adapted for bears. But of course, humans interact with bears much less than we do with dogs, so the bear version probably hasn't been developed or deployed.

As far as intelligence having a specifically normal distribution, though, that depends on having some way to quantify it. One can come up with some sort of test, and say that those animals with a higher score are more intelligent than those with a lower score, but can you say (for instance) that an animal with twice the score of another is "twice as intelligent"? Can you even say that one gap between scores is "twice as large" as another gap? Without being able to say things like that, you can't determine what sort of distribution you have. With human tests, in fact, the usual procedure is to feed the raw scores through a function designed to turn it into something that has a normal distribution, and then assert that that exactly-normally-distrubuted artificial statistic is "real intelligence".

Beckdawrek, you don't need to invoke calamities like abnormal births (which aren't as common among non-humans, anyway) to explain differences in intelligence. Animal intelligence would vary for all the same variety of reasons as human intelligence.
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Old 11-08-2018, 09:16 AM
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...As far as intelligence having a specifically normal distribution, though, that depends on having some way to quantify it. One can come up with some sort of test, and say that those animals with a higher score are more intelligent than those with a lower score, but can you say (for instance) that an animal with twice the score of another is "twice as intelligent"? Can you even say that one gap between scores is "twice as large" as another gap? Without being able to say things like that, you can't determine what sort of distribution you have. With human tests, in fact, the usual procedure is to feed the raw scores through a function designed to turn it into something that has a normal distribution, and then assert that that exactly-normally-distrubuted artificial statistic is "real intelligence".
But you make this sound rather more unscientific and ad hoc than it really is. There are many different possible tests you can do to measure cognitive ability. The notion of a general intelligence factor g arose from evidence that the results of a wide variety of such tests are positively correlated, with g explaining about half the variance.

And the assumption of a normal distribution is a reasonable one. Barring major mental defect (i.e. away from the tails of the distribution) the distribution of innate general intelligence is almost certainly attributable to the combined influence of variation at many genetic loci (a single gene with large effect would have been found), so the Central Limit Theorem implies a normal distribution.

There's a Wiki article on g in non-humans, apparently it's quite similar in primates and rodents, explaining about half the innate variance in cognitive tests.
https://en.wikipedia.org/wiki/G_factor_in_non-humans

Last edited by Riemann; 11-08-2018 at 09:20 AM.
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Old 11-08-2018, 09:21 AM
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A black bear cub/yearling was recently seen in my area running around with its head stuck inside a big plastic pretzel jar. Just saying.
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Old 11-08-2018, 10:11 AM
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Well, there have been incredibly smart bears like Yellow-Yellow who managed to figure out how to open food canisters designed to stop bears, and taught the methods to her offspring.
Except her oldest cub, Mellow Yellow, who didn't seem very interested in learning anything at all.
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Old 11-08-2018, 10:29 AM
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Well, yes, there's definitely some real trait there which can at least be ranked. And yes, a normal distribution probably is a reasonable assumption, absent any specific reason to use some other distribution. It's just not really a testable assumption.

There are also ways to do meaningful statistics on data without assumptions of distributions, using nothing more than rank data. And it behooves researchers to learn about those methods, because often (more often than statistician like to admit), the assumptions that lead to normality fail in one way or another (especially in the tails of the distribution).
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Old 11-08-2018, 12:02 PM
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Without knowing anything about how to measure intelligence or anything about bears I would be putting my money on a normal distribution. Is there any natural measurable trait of any species that is not normally distributed?

It seems the trick here is defining what is intelligence in a bear, and then determining how to measure it.
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Old 11-08-2018, 12:11 PM
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Except her oldest cub, Mellow Yellow, who didn't seem very interested in learning anything at all.
Quite rightly.
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Old 11-08-2018, 12:41 PM
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It seems the trick here is defining what is intelligence in a bear, and then determining how to measure it.
Well, as with humans (and the primate and rodent studies I noted above) the approach would be to devise numerous different cognitive tests, and then determine to what extent the correlation between the tests is explained by a general intelligence factor.
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Old 11-08-2018, 02:16 PM
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Quite rightly.

There ought to be a law.
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Old 11-08-2018, 02:19 PM
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I've seen YouTube videos. Bears can climb into hammocks and destroy suburban swimming pools. I think they might be coming to the end of a long period of just observing us and entering the "takeover" phase.
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Old 11-08-2018, 02:40 PM
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It seems the trick here is defining what is intelligence in a bear, and then determining how to measure it.
Also
Quote:
Bruce Schneier discusses the security issues related to bears in national parks, and quotes a park ranger:

There is considerable overlap between the intelligence of the smartest bears and the dumbest tourists.
Cite.

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Old 11-08-2018, 02:43 PM
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My assumption is that it would be a light-tailed distribution with very little variance and few outliers. They are not social creatures and there is some harsh selection against dumb ones.
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Old 11-08-2018, 03:28 PM
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My assumption is that it would be a light-tailed distribution with very little variance and few outliers. They are not social creatures and there is some harsh selection against dumb ones.
Why would selection against being dumb narrow the variance rather than increasing the mean?
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Old 11-08-2018, 03:57 PM
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Without knowing anything about how to measure intelligence or anything about bears I would be putting my money on a normal distribution. Is there any natural measurable trait of any species that is not normally distributed?
Sure, plenty. Number of limbs, for instance.
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Old 11-08-2018, 04:11 PM
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Sure, plenty. Number of limbs, for instance.
I'm not sure that's a good example. For most species, the number of limbs is not a genetically variable trait (excluding gross abnormality). For something like a centipede, it goes with body length and number of segments, so I wouldn't be surprised if it's approximately normally distributed.
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Old 11-08-2018, 04:58 PM
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Is there any natural measurable trait of any species that is not normally distributed?
You're evidently thinking of traits that are continuously variable. Of course there are many traits, like eye color in humans, that are not continuously variable. But even continuously variable traits can show bimodal or even fancier distributions.
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Old 11-08-2018, 08:17 PM
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One obvious example is height of humans, which also incidentally illustrates one of the dangers in the assumptions behind normality. Human heights are influenced by a wide variety of genes and environmental factors, which is usually what's described as needed for the Central Limit Theorem. But one of those genetic influences is almost purely discrete, with two values, and that causes the total distribution to be strongly bimodal, as well.
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Old 11-09-2018, 08:11 AM
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One obvious example is height of humans, which also incidentally illustrates one of the dangers in the assumptions behind normality. Human heights are influenced by a wide variety of genes and environmental factors, which is usually what's described as needed for the Central Limit Theorem. But one of those genetic influences is almost purely discrete, with two values, and that causes the total distribution to be strongly bimodal, as well.
You had me going there until I figured out what you were talking about.
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Old 11-09-2018, 08:40 AM
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A black bear cub/yearling was recently seen in my area running around with its head stuck inside a big plastic pretzel jar. Just saying.
So now they're armoring themselves. Great.
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Old 11-09-2018, 08:50 AM
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One obvious example is height of humans, which also incidentally illustrates one of the dangers in the assumptions behind normality. Human heights are influenced by a wide variety of genes and environmental factors, which is usually what's described as needed for the Central Limit Theorem. But one of those genetic influences is almost purely discrete, with two values, and that causes the total distribution to be strongly bimodal, as well.
Surprisingly, that's not the case. Human adult height distribution is not strongly bimodal, despite being a mixture of two normal distributions. The means are too close and the variance of each (especially males) too wide to yield twin peaks.

There's a cite here (scroll down to read the abstract).

Edit: you can read the paper in full here.

Last edited by hibernicus; 11-09-2018 at 08:55 AM. Reason: Link to paper
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Old 11-09-2018, 08:45 PM
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There's a distribution of intelligence in pretty much every mammal species. Why are you asking, specifically?

Except maybe koalas. They're exceptionally stupid as a rule.
{sarcasm on}
Are you saying that more than 50% of koalas have below average intelligence?
{sarcasm off}
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Old 11-10-2018, 03:00 PM
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A black bear cub/yearling was recently seen in my area running around with its head stuck inside a big plastic pretzel jar. Just saying.
Probably giving his Winnie the Pooh Halloween costume a dry run...
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Old 11-10-2018, 03:15 PM
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{sarcasm on}
Are you saying that more than 50% of koalas have below average intelligence?
{sarcasm off}
Somehow, yes. The few that evolved into drop bears bring up the mean.
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Old 11-10-2018, 10:17 PM
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Surprisingly, that's not the case. Human adult height distribution is not strongly bimodal, despite being a mixture of two normal distributions. The means are too close and the variance of each (especially males) too wide to yield twin peaks.

There's a cite here (scroll down to read the abstract).

Edit: you can read the paper in full here.
Well, that's using a particularly strong definition of "bimodal" that requires the means be different from each other by at least the sum of their standard deviations. That's certainly not the case for humans with respect to gender bias if you take the entire population of humans as the sample, as the variance of various groups of humans dwarfs the difference in average height between men and women. But if you were to looking at more restricted population than the American population as a whole, a population much more homogeneous, you might see a clearer double peak. Is it enough to satisfy the definition of bimodal used? Maybe not, but it's clear that women are on average shorter than men by a non-negligible amount and this is consistent across all human populations, so to describe the height of humans as bimodal isn't entirely wrong even if the definition technically excludes it.
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Old 11-11-2018, 08:25 AM
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Why would selection against being dumb narrow the variance rather than increasing the mean?
ISTM that it might bump the mean up slightly, due to loss of all the dumb bears, but it would leave a non-normal, one-tailed distribution behind. The variance would go down due to the loss of one tail, but most of the surviving bears would be of less than median intelligence.

Which leads me to wonder about just how much survival advantage there is to greater intelligence - beyond some arbitrary threshhold - in solitary animals.
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Old 11-11-2018, 09:16 AM
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ISTM that it might bump the mean up slightly, due to loss of all the dumb bears, but it would leave a non-normal, one-tailed distribution behind. The variance would go down due to the loss of one tail, but most of the surviving bears would be of less than median intelligence.
No, loss of one tail of the distribution could not happen when you consider the underlying mechanism that creates the normal distribution in a quantitative trait like intelligence. The normal distribution arises because the trait is due to small contributions from a large number of genetic loci. A simplified model would be: 100 genetic loci, each gene having two alleles, a "dumb" and "smart" allele. Higher than average intelligence is attributable to inheriting the "smart" allele are more of these loci than the average bear. Natural selection against being dumb would reduce the frequency of dumb alleles at each locus in the next generation. At some loci, the frequency of dumb alleles might go to zero, i.e. the smart allele would go to fixation.

So the initial effect of the selection pressure would be to increase the mean of the distribution; under strong selection pressure, if the smart allele went to fixation at a significant number of loci, the variance of the distribution would also narrow. New mutation at these or other loci that affect intelligence could increase the variance again over time.

The shape of the distribution would tend to become non-normal only if the trait comes under the influence of a small number of genes with large effect, rather than a large number of genes with small effect. For intelligence, this would mean a de novo mutation that arose (randomly, of course) in a single individual, making that individual much smarter, and then increased (non-randomly, through natural selection) in the population.

Last edited by Riemann; 11-11-2018 at 09:21 AM.
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Old 11-11-2018, 11:59 AM
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There's a distribution of intelligence in pretty much every mammal species. Why are you asking, specifically?

Except maybe koalas. They're exceptionally stupid as a rule.
You do know that Koalas are not bears?
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Old 11-11-2018, 12:00 PM
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If there's some threshold of dumbness, below which a bear is incapable of surviving to adulthood, and if you looked at the population of adult bears, you would indeed see one tail cut off of the distribution.

Quote:
Quoth brossa:

The variance would go down due to the loss of one tail, but most of the surviving bears would be of less than median intelligence.
By definition, exactly half of the surviving bears would be of less than median intelligence. You probably meant to say that most of them would be of less than the mean intelligence. Alternately, you could say that most of them would be of more than the modal intelligence.
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Old 11-11-2018, 12:10 PM
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Well, that's using a particularly strong definition of "bimodal" that requires the means be different from each other by at least the sum of their standard deviations. That's certainly not the case for humans with respect to gender bias if you take the entire population of humans as the sample, as the variance of various groups of humans dwarfs the difference in average height between men and women. But if you were to looking at more restricted population than the American population as a whole, a population much more homogeneous, you might see a clearer double peak. Is it enough to satisfy the definition of bimodal used? Maybe not, but it's clear that women are on average shorter than men by a non-negligible amount and this is consistent across all human populations, so to describe the height of humans as bimodal isn't entirely wrong even if the definition technically excludes it.
I think you are reading it backwards. It's not that they start with a narrow definition of "bimodal" that results in human height distribution not being bimodal. It's that a mixture of two distributions with different means can have a single mode (human adult height distribution being an example of that) and then they state the conditions under which this occurs.

Short version: the fact that women are on average shorter than men does not imply that the distribution of heights of all adults is bimodal.
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Old 11-11-2018, 12:15 PM
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Old 11-11-2018, 12:22 PM
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You do know that Koalas are not bears?
You do realize that was a joke? (In any case, he didn't actually say that koalas were bears.)

Drop bears are also not true bears.
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Old 11-11-2018, 12:46 PM
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Actually, I can think of another common human population which does have a bimodal height distribution: The heights of students (or especially, of boys) in a middle school. Some have hit their growth spurts, some haven't, and the spurts are quick enough that at any given time, very few are in the midst of one.
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Old 11-11-2018, 01:05 PM
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If there's some threshold of dumbness, below which a bear is incapable of surviving to adulthood, and if you looked at the population of adult bears, you would indeed see one tail cut off of the distribution.
No, this is wrong. For a quantitative trait influenced by a large number of loci all with small effect, at equilibrium you will never see a cut-off normal distribution except at the extreme tail where the cutoff is so far below the mean that very few individuals are born below the cutoff, and it has no significant effect on allele frequency.

Suppose that some new environmental challenge arises imposing extremely strong selection against intelligence below x that's (say) 1SD below the mean of the prior normal distribution. Now, of course, in that generation bears below 1SD are all dead, so you temporarily see a normal distribution cut off at -1 SD. But if this is a trait under the influence of a large number of loci with small effect, the effect on the next generation will be a lower frequency of "dumb" alleles at the large number of loci that influence intelligence. So in the next generation, you will see a new approximately normal distribution with a higher mean and smaller variance, chopped off at intelligence level x that is now more than 1SD below the mean of the new distribution. If the strong selection pressure is maintained for intelligence below x, in successive generations the frequency of dumb alleles is reduced further, so the mean of the distribution is pushed higher and its variance is reduced, until the cutoff point x is so far below the mean that so few individuals are below the cutoff that it's not having any further significant affect on allele frequency. So the new equilibrium is still approximately normal, cut off at x which is now at the extreme tail of the distribution, with very few individuals born with intelligence below x.

Last edited by Riemann; 11-11-2018 at 01:10 PM.
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Old 11-11-2018, 01:13 PM
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You do know that Koalas are not bears?
Are sea stars not made of plasma!?!?

But in all seriousness, koalas are very stupid by animal standards. Their brains are tiny and smooth (=less surface area per volume). They are obligate on eucalyptus but fail to eat the leaves if they are picked. Infested with chlamydia. Yeah they're sort of cute, but missed buying tickets to the genetic lottery.

The lowest brain to body ratio is the bony-eared assfish. They already have small brains, no need to kick them while they're down.

As far as what is a bear and what isn't, I'm still recovering from being constantly told as a child that giant pandas are not true bears. Turns out they are.
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Old 11-11-2018, 01:31 PM
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And water bears, ant bears, and honey bears are also not true bears.
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Old 11-11-2018, 02:21 PM
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Nor was Bear Bryant.
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Old 11-11-2018, 06:22 PM
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Really, the more unrealistic part of a cut-off threshold is that in reality, such thresholds are never sharp. You'll have some dumb bears surviving just by luck, while smarter bears than them still manage to dumb themselves to death.

And I'm really surprised that nobody has made a joke yet about bears themselves having short tails.
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Old 11-11-2018, 08:23 PM
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Drop bears are also not true bears.
Too right - they are notoriously deceitful, and sometimes outright lie.
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Old 11-12-2018, 06:55 AM
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Little known fact:

Highway signs that read "Bear Left" have nothing to do with bears.
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Old 11-12-2018, 07:45 AM
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Yeah, when you see one of those, usually the bear is still there, and didn't leave at all.
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Old 11-12-2018, 08:31 AM
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Too right - they are notoriously deceitful, and sometimes outright lie.
In fact, some bears lie like a rug.

I'll be here all week. Try the veal, and be sure to tip your waitress.

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Old 11-12-2018, 08:46 AM
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Really, the more unrealistic part of a cut-off threshold is that in reality, such thresholds are never sharp. You'll have some dumb bears surviving just by luck, while smarter bears than them still manage to dumb themselves to death.
.
Still nope. For a quantitative trait under the influence of many loci, so long as there is any significant selection against bears in the lower part of the intelligence distribution, the selection will keep removing dumb alleles, which will keep pushing the mean of the distribution higher and narrowing its variance until a new equilibrium is reached. Equilibrium occurs when there is no longer any significant change in allele frequency due to selection, which means a new two-tailed approximately normal distribution where only an insignificant number of bears are born with low enough intelligence to have a significant fitness penalty.
  #49  
Old 11-12-2018, 08:53 AM
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The real question is going to be, how do you measure and score bear intellegence. Intelligence isn't like height and weight, that has a physical existence and natural scale on which to measure it. Its measure and scale can only be defined in terms of the results on a test. The distribution you get depends entirely on what that test is.

If you test is based purely on a single act of getting a container open, then intelligence is a binary variable. If it measured by "how long does it take to get the container open, then it might have have a short left hand tail and long right hand tail. If its measured by the numbers successes or failure on a large set of unrelated tasks than it is likely to look approximately normal.

The current method of measuring intelligence is performance on a standardized test, which in the case of bears is likely to have a very high peak at "ignore" but a small bump in the vicinity "tore up and attempted to eat test"

Last edited by Buck Godot; 11-12-2018 at 08:56 AM.
  #50  
Old 11-12-2018, 09:48 AM
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Quote:
Originally Posted by Buck Godot View Post
The real question is going to be, how do you measure and score bear intellegence. Intelligence isn't like height and weight...
See post #8, and Wiki articles on “g”. There is an empirical correlation among a wide variety of cognitive tests in both humans and animals, general intelligence is the factor that explains about half the variance.

Last edited by Riemann; 11-12-2018 at 09:50 AM.
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