Donnerstag, 30. April 2015

Speed and Accuracy (Part1):

This guy (probably in his late forties, or in his fifties) teaches us how to throw frisbee like a Pro. It is not unlikely that two of his sons can throw a frisbee as fast and far (if not even faster and farther) as he can. Nevertheless, when you look at the video, you get easily the impression that his throws are much more accurate than the throws of his sons. So my hypothesis would be: experience matters much more for throwing accuracy than it matters for throwing speed.

The fluid intelligence / mental speed of a person peaks at the age of about twenty. But at the age of twenty there are not many persons who have much experience. That's the reason why, regarding some/many topics, the judgments of the thirty or forty year olds seem to be more accurate than the judgments of the twenty year olds.

[World records in javelin throw "measure" throwing speed, but do not "measure" throwing accuracy:  Uwe Hohn broke the world record at the age of 22 (1984), ... Patrick Boden broke the world record at the age of 22 (1990);  Steve Backley broke the world record at the age of 21 (1990) and at the age 22(1992); Jan Železný broke the world record at the age of 20 (1987), 26 (1993), 27 (1993) and 29 (1996).]

[See also: Speed and Accuracy (Part2)]

Sonntag, 26. April 2015

The more g-loaded, the more heritable, evolvable, and phenotypically variable: Homology with humans in chimpanzee cognitive abilities

The more g-loaded, the more heritable, evolvable, and phenotypically variable: Homology with humans in chimpanzee cognitive abilities
Michael A. Woodley of Menie, Heitor B. F. Fernandes, William D. Hopkins; (2015)


We computed g-loadings for 13 cognitive tasks in chimps to test Jensen effects.
We calculated phenotypic and additive genetic variance for each task.
We obtained h2 of cognitive abilities from the same sample of chimpanzees as Hopkins et al. (2014)
The four variables were positively, strongly related, expanding on studies in humans.
Tool use showed signs of strong selection pressures in line with Primate-wide studies.


Expanding on a recent study that identified a heritable general intelligence factor (g) among individual chimpanzees from a battery of cognitive tasks, we hypothesized that the more g-loaded cognitive abilities would also be more heritable addition to presenting greater additive genetic variance and interindividual phenotypic variability. This pattern was confirmed with multiple analytical approaches, and is comparable to that found in humans, indicating fundamental homology. Finally, tool use presented the highest heritability, the largest amount of additive genetic variance and phenotypic variance, consistent with previous findings indicating that it is associated with high interspecies variance and has evolved rapidly in comparative primate studies.

Freitag, 24. April 2015

Historical Videos:

Those videos give an impression of the "Old Europe".
(It's also fascinating how many people wore hats a century ago.)



Dienstag, 21. April 2015

Covariation between human pelvis shape, stature, and head size alleviates the obstetric dilemma

Covariation between human pelvis shape, stature, and head size alleviates the obstetric dilemma; Barbara Fischer and Philipp Mitteroecker (2015)


Because of the tight fit of the large human neonate through the narrow maternal birth canal, childbirth is remarkably difficult. In this study we show that the dimensions of head, stature, and pelvis in a human body are linked in a complex way that was not recognized before and that contributes to ameliorate this tight fit. We show that females with a large head possess a birth canal that can better accommodate large-headed neonates. Because mothers with large heads usually give birth to neonates with large heads, the detected pattern of covariation contributes to ease childbirth and has likely evolved in response to strong selection.


Compared with other primates, childbirth is remarkably difficult in humans because the head of a human neonate is large relative to the birth-relevant dimensions of the maternal pelvis. It seems puzzling that females have not evolved wider pelvises despite the high maternal mortality and morbidity risk connected to childbirth. Despite this seeming lack of change in average pelvic morphology, we show that humans have evolved a complex link between pelvis shape, stature, and head circumference that was not recognized before. The identified covariance patterns contribute to ameliorate the “obstetric dilemma.” Females with a large head, who are likely to give birth to neonates with a large head, possess birth canals that are shaped to better accommodate large-headed neonates. Short females with an increased risk of cephalopelvic mismatch possess a rounder inlet, which is beneficial for obstetrics. We suggest that these covariances have evolved by the strong correlational selection resulting from childbirth. Although males are not subject to obstetric selection, they also show part of these association patterns, indicating a genetic–developmental origin of integration.

[via Steve Stuart Williams]

Dienstag, 14. April 2015

Interview with Arthur Jensen:


[See also: part2]

Are within-sex mating strategy phenotypes an evolutionary stable strategy?

Are within-sex mating strategy phenotypes an evolutionary stable strategy?
Rafael Wlodarski & Robin I. M. Dunbar (2015)


Humans have been found to display considerable variety in their pursuit of mating strategies, varying in their preference for short-term mating encounters versus established long-term relationships. While we know that differences in mating strategy exist between the two sexes (as predicted by parental investment theory), it has recently been shown that each sex may further exhibit two mating phenotypes. Here we explore the possibility that the presence of two phenotypes may be frequency dependent, thus comprising an Evolutionary Stable Strategy (ESS). We suggest that the presence of these phenotypes reflects a compromise between male preference for promiscuity and a female preference in favour of long-term mating by males.

Sonntag, 12. April 2015


It doesn't seem as if those IS idiots are able to create something beautiful, meaningful or valuable, but they have a well developed capacity to destroy it:

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[Currently just the pixelated version of that video is online; The original version was removed from youtube. (for whatever reason)]

Donnerstag, 9. April 2015

Predictability and redundancy of natural images

Predictability and redundancy of natural images
Daniel Kersten (1987)


One aspect of human image understanding is the ability to estimate missing parts of a natural image. This ability depends on the redundancy of the representation used to describe the class of images. In 1951, Shannon [Bell. Syst. Tech. J. 30, 50 (1951)] showed how to estimate bounds on the entropy and redundancy of an information source from predictability data. The entropy, in turn, gives a measure of the limits to error-free information compaction. An experiment was devised in which human observers interactively restored missing gray levels from 128 X 128 pixel pictures with 16 gray levels. For eight images, the redundancy ranged from 46%, for a complicated picture of foliage, to 74%, for a picture of a face. For almost-complete pictures, but not for noisy pictures, this performance can be matched by a nearest-neighbor predictor.

Sonntag, 5. April 2015

Human Reproduction & Regression to the Mean:

(o) I know some families with five, six, or seven* children. How many generations will it take until their descendants family size/reproduction rate comes quite close to the country's average family size/the average person's reproduction rate?

(o) For historical times (e.g. the last 165 years): How fast did reproduction rates regress toward the mean?

* a parent of such a family has about five times as much children as the average German (~1.4) and about 3.5 times as much children as the average German parent; Although it is said that the average German woman has 1.4 children, women of German descent have less children (~1.1, Birg). Childlessness occurs frequently. For that reason the average German family has 2 children (and not just one).

Samstag, 4. April 2015

Does the Regression to the Mean in IQ reflect a Regression to the Mean in g?

According to Cochran, regression to the mean in IQ isn't just a purely statistical phenomenon, but also a real phenomenon: The children of people with high/extreme IQ-scores usually get, on average, lower/less extreme IQ-scores. (To 'exclude' the possibility that the regression to the mean is just caused by measurement errors, both parents and their children should be tested several times.)
So, if the regression to the mean in IQ doesn't reflect a regression to the mean in g, the following should be found: The less g-loaded an item of the IQ-test, the more regression to the mean; the more g-loaded an item of the IQ-test, the less regression to the mean.

Donnerstag, 2. April 2015

Is systemizing a feature of the extreme male brain from an evolutionary perspective?

Is systemizing a feature of the extreme male brain from an evolutionary perspective?
Jennifer Byrd-Craven, Amber R. Massey, Jessica L. Cali, and  David C. Geary
Personality and Individual Differences (Aug 2015)


o Systemizing has been proposed as essential difference between men and women.

o We tested the hypothesis that systemizing captures interest in novel niches.

o Occupational interests capture some variance in sex differences in systemizing.

o Systemizing is unlikely to reflect an essential sex difference.


Sex differences in empathizing with others and systemizing the abstract rules that govern the operation of things and the natural world have been proposed as the core, essential differences between men and women. We evaluate this assertion in the context of Darwin’s (1871) sexual selection and specifically test the hypothesis that the systemizing measure captures interest in evolutionarily novel occupational niches associated with interests in science, technology, engineering, and mathematics (STEM). Young adults (n = 233, 149 male) completed the Empathizing Quotient (EQ), the Systemizing Quotient (SQ) and the RIASEC Personality Type Inventory to assess six career interest groups. Sex differences were found on the EQ, SQ, Investigative interests and interest in things, a subset of items from the Realistic scale. Mediation analyses revealed that occupational interests partially mediated the relation between sex and SQ scores, whereas controlling for Investigative interests increased the sex difference in EQ scores. These results provide partial support for the hypothesis and suggest SQ captures, in part, occupational interests in evolutionarily recent STEM fields.

Mittwoch, 1. April 2015

Why Interindividual Variability in Intelligence Matters:

"A population with little intellectual variance but homgeneously centered around an average level of ability, say, with 90% of persons having IQs between 90 and 110 (the range that now contains the middle 50% in the United States Caucasoid population), if left to itself, would probably advance very slowly, if at all, beyond a Stone Age or simple agrarian culture. As a factor in cultural evolution, the amount of variability of talents in a population could be more important than its overall mean."

Arthur R. Jensen (1978)
Human Variation - Genetic and Behavioral Effects of Nonrandom Mating