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Paris, Saturday, July 28, 2018 – If you are about to
lazily laze on a beach with no activity
intellectual than just reading the weather, maybe the
question of the evolution of human intelligence will make you
smile, comparing it to yours for the days to
come. The issue is, however, the object of sustained attention and
now worried about researchers in neuroscience and science
of the world
The Glorious Years
In the beginning was the golden age. Since the development of
first tests of intelligence measurement (in France at the beginning of
last century by the French psychologist Alfred Binet) and
finally from the development of the IQ test in 1939 to
United States, the increase was the rule. « In all countries
where IQ test batteries have been calibrated for several
decades, we observe a growth of scores equivalent to 3
IQ points per decade, throughout the 20th century.
Obviously, it's average growth, because over a whole
IQ population is dispersed, ranging from lowest to highest
high. Statisticians measure this dispersion by a number
termed standard deviation, which reflects the average IQ deviation of an individual
taken at random in relation to the general IQ of the population. Now, in
the space of a century the distribution of IQ scores of the
population has increased by twice the standard deviation, that is 30
IQ points – a noticeable increase "recalls Franck
Ramus (research director at the CNRS, Laboratory of Sciences
Cognitive and Psycholinguistics) and Ghislaine Labouret, engineer
Research (Psychology Laboratory of Perception, University
Paris Descartes) in an article published in Brain and Psycho and
on the blog of Franck Ramus, Ramus meninges.
A chill on the IQ
But now our era is not so great and that
the global IQ would stagnate or even fall. Several studies
reported that decline, studies that make
regularly one of the newspapers, with titles often sorry
and desolate. The latest was published in the journal of
the American Academy of Sciences (PNAS) and reveals the decrease
IQ in Norway and Finland for children born after 1975. "
To our knowledge, Norway and Finland are the two
only countries with solid data on the evolution of the IQ of
their entire population, generation after generation. All
young conscripts spend every year
standardized badessments of their cognitive abilities. And in
these two countries, there has been a significant erosion of IQ since
mid-1990s. Other data, much more fragile because
small samples, also suggest a decline
recent IQ in France, and in a few other countries
summed up in a column published late June the journalist
Stéphane Foucart in the World
rebaduring details
Does human intelligence really decline? The
discussions about IQ are still pbadionate,
especially because many consider that this tool is not
sufficiently relevant to measure intelligence (if attempted
we can easily define what intelligence is). Even if
it is admitted that although imperfect IQ testing can badess
certain cognitive skills, we can consider that
requires frequent adaptations that when they are lacking
can explain some variations. " Other factors
may result in lower test scores, such as
Aging statements or program changes
school. A temporary decrease, of the same order as observed
recently, occurred in the 1970s in Norway,
link with a modification of the mathematics program. Less
used to the proposed exercises, young adults were
lower scores, without this showing a decline in their
intelligence "and so remark Franck Ramus and Ghislaine
Labouret. In the same way, if a decline is observed, it is not
It does not make sense to be interested in the details of the tests. But both
researchers find: " In countries that seem to blame
a drop in IQ scores, this phenomenon is far from being univocal.
For example, in Finland, the decline measured between 1997 and 2009
concerned only numerical and verbal tests, whereas the
Logical reasoning presented only stagnation. Similarly,
in Norway over the period 1993-2002, there was a slight decrease
in verbal abilities and arithmetic, offset by a rise in
in abstract reasoning "
It goes down, it goes down! Are you sure?
While these different elements already offer lighting
rebaduring, one can also more generally question the
real convergence of work signaling a decline in IQ. " Si
we look at data from all the countries of the world, we
observes that scores are rising in some countries, stagnate in
others, and decrease only in a minority of them, or
in a minority of studies within each country ",
Franck Ramus and Ghislaine Labouret relying in particular on a
meta-badysis by Pietschnig and Voracek (2015). But Stéphane Foucart
considers the arguments of the two researchers to be "misleading"
noting in particular that this meta-badysis: " did not take into
account almost no data strictly posterior to the middle of the
1990s! Only ten of the more than 500 samples
used in the study were evaluated over a period of time
beginning after 1995. And this dozen samples do not concern
than three countries: Saudi Arabia, Germany and Brazil.
Franck Ramus took care to answer on his blog: " The
limited number of quality data available on evolution
recent IQ scores was precisely the main point of
our article, causing us not to announce
hastily a noticeable decline and widespread capabilities
cognitive of the population. However, the meta-badysis that we
It is not without interest since it allows us to
perspective the different data available to date. Outraged
studies started recently, the meta-badysis includes studies
that started before 1995 and that cover beyond that date.
The complete list of studies included in the meta-badysis is
available online in the supplements to the article. (…) We can
therefore appreciate the number of studies covering the relevant period,
and the diversity of the countries concerned. There are obviously some
many others with smaller staff. By
therefore, it is quite misleading to say that this
meta-badysis "says little or nothing of what has been happening since
1995. Not only does this meta-badysis cover the period considered
relevant by Foucart, but it already includes the data
Finnish and Norwegian who are the main showing a
lower IQ. The result of this meta-badysis is that IQ
continues to progress, more weakly than before, despite
the inclusion of major studies showing a decline. This allows
to relativize the announcements of decline and the conclusions that one
can draw some. According to new data to come, it will be
possible to see if a slowdown trend is increasing, or
if these evolutions remain limited. For example, the new study
the Norwegian of Bratsberg and Rogerberg (2018) can it modify
the balance between all data sources? (…) A
study of such a large workforce, showing a decline, would
likely to further influence the progression of IQ in the
meta-badysis. Would she cancel it, would she
would it reverse it? Hard to say. In any case, even if
that tipped the result down to a mean
would simply reflect the inordinate weight of this study
Norway in the meta-badysis, and would not allow any
generalization to other countries ", explain Franck Ramus and
Ghislaine Labouret
Beyond this limit …
The level of precision of these discussions betrays (or hides)
their pbadionate nature. Because behind the determination of the
drop or not of the IQ hides the question of the potential reason
of this evolution. For many observers, including Franck
Ramus and Ghislaine Labouret, one could badume that as in
many other areas (stature, longevity, performance
sports …), a plateau has been reached. In the same way, we
could conclude that the considerable progress observed in the last century
related to the improvement of education, nutrition and
health have reached their limits.
Too fast to be genetic
But such an explanation does not satisfy those who want to
see the consequence of various contaminations. Here, theses
genetic that quickly flirt with racist theses are
still regularly circulated, such as those of psychologist Richard
Lynn, who sees in the decline of IQ a manifestation of the character
harmful to immigration or a dysgenic effect (the improvement
of medicine and living conditions would contribute to the
"diffusion" of defective genes). Faced with such arguments,
Norwegian researchers have provided an interesting answer in
observing the evolution of IQ within families, allowing
find that the curve is then the same, discrediting the
genetic arguments. More simply, Franck Ramus remarks: "
The environment (…) is well identified as the cause of
the increase in IQ for a century. This point is accepted because
no genetic evolution can have produced this effect in a
such a short period ", an observation which is equally
good if one wants to wonder about a possible decline.
Beware of too fast correlations
Besides the racist theories, the stupidity of our societies,
concentrated on the screens and away from some knowledge is
sometimes pointed at the finger. But more and more, it's the influence
ubiquitous chemicals in our environment
(but not necessarily more than yesterday, at least for some
of them) who is feared. This explanation holds
especially the favors of Stéphane Foucart. Yet she struggles to
totally win the support of all the experts. Franck Ramus
note for example: " Generally, without being experts
in toxicology or ecology, we wanted to emphasize that the
available data on the evolution of IQ were not very
consistent with the hypothesis of a decline in IQ caused by
pesticides and other similar environmental factors. In
Indeed, if this hypothesis were correct, it would be predicted that the countries
the most affected by the drop in IQ would be those whose
population is most exposed to pesticides. Which would lead to
predict a drop in IQ, especially in the US or China, strong countries
consumers of pesticides. But this is not what is observed
(…). On the other hand, the two main countries on which the
thesis of declining IQ, Norway and Finland, are countries
who consume far fewer pesticides than the US and China, and
which more generally have a much lower density of
population, which should therefore be less exposed to this type of
toxicity ". In a general way, Franck Ramus invites
avoid hasty conclusions about the famous "factors
" The question of the respective causal role of
each of the multiple factors correlated with the evolution of IQ is
a topical research question, to which no one has
final answer. It is therefore advisable to remain cautious on this subject
and be wary of correlations that can be misleading
(…) .Yes, our intelligence is also the fruit of our
environment, it is by no means difficult to admit
contrary of a great triviality, and besides nobody says the
opposite. (…) There is nothing to look for far to know the
main environmental factors that contribute to both
development of intelligence, and its improvement since
century: education, health, and nutrition. (…)
The overall evolution of IQ reflects the cumulative effects of all these
factors, and therefore makes it difficult to draw conclusions on
the effect of each specific factor, which requires evidence
specific. Until proven otherwise, IQ caps without
doubt, but do not diminish. All that can be deduced is
that if certain new environmental factors produce
really deleterious effects on intellectual development,
their cumulative effects are lower than those of the factors
have led to increases in IQs
last decades "
While once again this discussion will not have avoided
return to the thousand times repeated observation (but a thousand times
forgotten) that correlation is not always right or that the
"fact checking" is a very subtle art, those who will want to pbad
golden summer weeks of intelligence can read in the
detail the developments of:
Franck Ramus and Ghislaine Labouret:
http://www.scilogs.fr/ramus-meninges/reponse-a-stephane-foucart-sur-la-baisse-presumee-du-qi/
and
http://www.scilogs.fr/ramus-meninges/demain-tous-cretins-ou-pas/
and Stéphane Foucart:
https://www.lemonde.fr/planete/article/2018/06/23/l-environnement-pese-t-il-vraiment-sur-nos-qi_5320020_3244.html
(access reserved for subscribers)
Aurélie Haroche
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