Chapter 7: Cognitive Intelligence and Thinking

Welcome to Last Minute Lecture.

This free chapter overview is designed to help students review and understand key concepts.

These summaries supplement not replaced the original textbook and may not be redistributed or resold.

For complete coverage, always consult the official text.

Welcome back to The Deep Dive.

For, well, for centuries, we have placed intellectual capacity, reasoning, and logic on this incredibly high pedestal.

And we usually assign all of that to the left hemisphere of the brain.

The common wisdom, you know, it tells us the left brain is the smart one.

The analytical powerhouse.

Exactly, the part that fuels IQ.

But today, we are going to challenge that foundational assumption completely.

Yeah, our sources, and they're drawn from this really profound synthesis of neuroscientific research, psychological measurement, and philosophical history.

They suggest that this popular belief isn't just a little bit off.

Right.

It's fundamentally inverted.

That's right.

Our mission in this deep dive is to explore the claim that the right hemisphere may actually contribute the majority of what we understand when we talk about genuine cognitive intelligence.

Or that legendary G factor.

Yeah, exactly.

We're moving beyond those simple, you know, left brain, right brain cliches to really understand how these two modes of attention actually tackle the world.

We are going to unpack the cutting edge evidence for right hemisphere dominance in what's called fluid intelligence.

And then we'll track this fascinating historical paradox of why IQ scores were rising for decades.

The Flynn effect.

The Flynn effect, yes.

And then we have to confront the pretty sobering evidence that despite those historical gains, our deepest, most flexible forms of cognitive thinking are now diminishing in Western society.

Researchers are calling it the reverse Flynn effect.

That's the one.

It is a dense, but I brain maps and lesion studies all the way to cultural shifts in education and attention.

So let's unpack this and find out what the changing landscape of our minds really means for our future.

Okay, so we have to begin by sort of resetting the definition of intelligence itself.

Right.

Because the sources immediately draw this distinction between the common assumption and, well, the actual thing.

Most people equate intelligence with analysis, verbal skill, calculation.

All things we typically assign to the left hemisphere, the LH.

Exactly.

But the sources define true intelligence as something much, much deeper.

The crucial distinction here is between following a procedure and achieving understanding.

The left hemisphere is a master of procedure.

Okay.

Its strong suit is executing familiar sequential steps.

But true intelligence, that's about grasping the full context, the meaning, the implication of something.

Right.

So if you're truly intelligent, your knowledge isn't just a checklist of facts.

That's it.

True intelligence is revealed in creativity.

It's the ability to take the knowledge you have and see how to apply it or adapt it to a totally novel problem.

A new problem.

Exactly.

If you've seen the problem before, you just use a procedure.

You pull out the recipe.

You pull out the recipe.

But if you haven't, you need genuine insight.

And the LH is simply not equipped for that kind of novelty in the same way the RH is.

This distinction is, it's just so crucial for understanding the brain's specialized modes.

Well, the sources suggest that as intelligence increased through our evolution,

we needed to develop this specialized tool, a kind of virtual world where we could manipulate concepts and symbols.

And that became the LH mode.

That became the LH mode.

It's an abstraction, a representation of the world, and it's designed for specific, focused tasks.

I like the computer analogy the source offers here.

The development of high intelligence allowed us to create computing systems.

And computers aid our intelligence, right?

They perform complex procedures.

They process symbols, store tons of data.

But the computer isn't the source of the intelligence.

No, it's a tool.

It's an auxiliary tool.

And the LH, while obviously infinitely more complex than a computer, functions in a similar way.

It's like an emissary, an intermediary.

It's much better at carrying out procedures and manipulating symbols like words and numbers than it is at understanding the meaning and context behind them.

And this leads us directly to the definition of what psychologists are actually trying to measure.

In 1994, Linda Gottfredson and 52 leading experts, they published this consensus definition in the Wall Street Journal.

And this is vital because it moves beyond just, you know, academic test -taking ability.

Exactly.

They defined intelligence as a very general mental capacity.

OK, so what does that include?

It involves the ability to reason, plan, solve problems,

think abstractly, comprehend complex ideas, learn quickly, and learn from experience.

So it's about catching on.

It's about catching on or figuring out what to do when you're confronted with something new.

That holistic, adaptive, non -procedural understanding is the real target.

And the single most reliable statistical measure that correlates with this broad holistic definition is the G factor, right?

General intelligence.

Yes.

And this is one of the most robust findings in all of psychology.

G behaves as a single factor underlying all cognitive assessments.

If you excel in one area with cognitive testing, you're highly likely to excel in others.

It suggests there's a fundamental underlying engine of mental capacity.

That's right.

Now, to understand G better, we have to distinguish its two components.

First, there's GC,

or crystallized intelligence.

Right.

This is the knowledge base, the accumulation of facts, vocabulary, skills you build through

education, experience, your cultural context.

It's what's on your mental hard drive.

Exactly.

Yeah.

And then we have gref, or fluid intelligence.

And this is the raw engine.

This is the raw engine.

Gref is intelligence in and of itself.

It's the ability to apply reasoning and problem solving to novel situations.

Situations where your crystallized knowledge, your GC, can't give you an immediate familiar procedure.

Yes.

Because it's applicable to any new context, it's the least culture bound measure, and it's widely considered the best correlative of intrinsic experimental capacity.

So if gref is the gold standard for raw intrinsic intelligence and novel problem solving,

where does the neuroscientific evidence point?

And this is where the standard narrative is completely overturned.

We can turn to a major study from the Decision Neuroscience Laboratory at the University of Illinois.

They were focusing on Gareff tests, which they noted are the best tests of G, and highly predictive of broad success in life.

And they studied patients with brain lesions.

That's right.

158 patients with brain lesions to see which parts of the brain, when they were damaged, most impaired gref.

And the finding was?

What?

It was striking.

They concluded that gref was associated with a broadly distributed network of brain regions.

But, and this is the crucial part, this network was located primarily within the right hemisphere.

Primarily in the right, wow.

This is a fundamental challenge to that whole LH dominance narrative.

The researchers suggested that gref reflects the ability to effectively integrate verbal, spatial, motor, and executive processes across the brain.

So it's about integration.

It's all about integration.

And that capability relies heavily on a specific set of cortical connections, these long white matter tracks, found primarily in the right hemisphere.

So we're talking about the infrastructure for rapid holistic connection.

The study highlighted the superior longitudinal fasciculus and the arcuate fasciculus.

Both in the right hemisphere.

Both in the right hemisphere as being particularly significant for general intelligence.

You can think of these as like the high speed information superhighways that let the brain quickly pull together all these disparate pieces of information to form a holistic understanding.

Which is exactly what you need for novel problem solving.

Exactly.

And we can reinforce this by looking at how the hemispheres handle working memory.

When researchers map brain activity, they find this really clear division of labor that aligns with the right hemisphere's role as the comprehensive monitor.

So the monitoring of information and spatial representation, taking in the overall picture, understanding where things are in relation to one another.

That's almost entirely dominated by the right hemisphere.

Right.

Meanwhile, manipulating that information, you know, running the calculations, dealing with the representation in words and numbers.

That's almost entirely dominated by the left hemisphere.

Exactly.

The LH manipulates the symbols.

The RH monitors the context and the meaning.

So the pattern suggests the LH is, yeah, the capable symbolic intermediary, but the RH is the executive.

It's the one processing the spatial and informational context required for true understanding.

And this observation is supported by broader literature, isn't it?

It is.

Reviews of intellectually gifted subjects show they demonstrate more prominent right hemisphere activation than average controls.

And this holds true even when the subjects are doing tasks we think of as LH dependent, like language exercises.

Even then.

High intellectual engagement requires enhanced coordination between hemispheres, of course, but that right hemisphere activation is really the signature of the gifted mind.

So the takeaway from this first section, even before we get into the paradoxes, is clear.

For the most flexible, sharpest, most fundamentally intelligent cognitive abilities, that grief factor, the right hemisphere, is the preponderant engine.

So to truly test this idea that the RH carries the intellectual heavy lifting,

scientists look at damage.

Right.

Specifically, the surgical removal of one hemisphere, a hemispherectomy.

It's a dramatic real world experiment, but it's complex, you know, due to the brain's remarkable plasticity, especially in kids.

Yeah, that makes sense.

So what does the data say?

Well, the data is scarce, but early reviews offered some hints.

One review noted that full scale IQ is lowered, regardless of which hemisphere is removed.

But the impact on IQ was consistently less severe when the left hemisphere was the one ablated.

Less severe when the left was removed.

Yes.

The brain, and particularly the right hemisphere,

seems able to compensate better for the loss of the LH than the other way around.

There are some anecdotal cases that are just astounding.

The source mentions a case where one patient developed above normal language and intelligence after a left hemispherectomy.

That's amazing.

It is.

The brain reorganized to accommodate the loss of the verbal center, which suggests the raw capacity for intelligence remained intact, or maybe even flourished once it was freed from the LH's procedural focus.

And a small recent pediatric study seemed to emphasize this trend.

Of five patients who had a left hemispherectomy, only one showed a significant drop in IQ.

Only one of five.

But of the two children who had a right hemispherectomy.

Both of them showed a drop.

Both showed a significant drop in IQ.

It really seems the loss of the RH is consistently more detrimental to core intelligence.

Now we do have to include the caveat you mentioned.

Plasticity.

Brain plasticity, especially in early childhood, is immense.

And a much larger follow -up study, which was designed to be more rigorous,

didn't find a significant long -term difference based on the side of the hemispherectomy.

That's right.

The brain is incredibly adaptive.

But the suggestive data just keeps pulling the focus back to the RH.

So to get around the complication of plasticity and also the cultural factors in IQ tests, researchers look for physiological measures.

Biological markers.

Things that are free from train effects and correlate closely with G.

And this is where we look at the speed of the mind.

The most reliable of these physiological markers is simple reaction time, RT.

This is a purely neurological measurement.

How quickly can a person respond to a basic, singular stimulus like pressing a button when a light comes on?

Simple RT is culturally neutral, requires no prior knowledge, and it directly correlates with information processing speed.

Shorter reaction times strongly associate with general intelligence.

And interestingly, that correlation gets stronger as a person ages.

It does.

Which suggests it's a really reliable baseline marker for cognitive capacity.

The other surprising physiological marker that correlates so highly with G is color discrimination or acuity.

Yeah, the ability to distinguish between very slight variations in color.

The source notes a stunning correlation here.

What is it?

Estimated between 0 .7 and 0 .9.

Wow.

That's incredible.

It is.

And critically, color acuity is associated with the right hemisphere.

So the researchers had to ask, if color acuity, a measure associated with the Rh,

is so predictive of G, what about simple reaction time?

Is that processing speed engine also primarily in the Rh?

And what did they find?

Early studies of brain damage patients found a remarkable and clear pattern.

Patients with right hemisphere damage showed a much greater impairment on simple reaction times than patients with left hemisphere damage.

Much greater.

So the initial assumption by the researchers was, okay, this is going to be a volume issue.

The Rh lesions must just be bigger.

They must be bigger.

But when they performed a rigorous metric analysis, they found the opposite.

The Rh lesions were, on average, smaller than the Rh lesions.

Wait, wait.

So despite having less brain damage by volume, the Rh damage patients showed a significantly greater loss in raw processing speed.

That's it.

That's a powerful piece of evidence.

It leads to a clear inference.

The right hemisphere is, in some fundamental way, functionally dominant for simple reaction time.

It's the engine that sets the fundamental pace and capacity for guff.

And we can track this dominance even into what many consider the pinnacle of human intellect, mathematics.

But again, we have to clarify here.

Right.

We are not talking about rote computational skill doing your times tables.

That's procedural.

That's the LH.

That's the LH.

Yeah.

We're talking about mathematical reasoning ability, the capacity to see and manipulate complex patterns and structures.

And that ability is strongly linked to the enhanced development and activation of the right hemisphere.

It is.

Studies on mathematically intelligent children show significant differences in activation in three specific cortical areas.

The inferior parietal lobule, the post -central gyrus, and the premotor cortex.

All in the right hemisphere?

All squarely in the right hemisphere.

So all this cumulative evidence helps us draw this vital contrast between human intelligence and machine intelligence, AI, which is maybe the most potent illustration of the LH mode.

Absolutely.

AI is modeled on the serial, logical, step -by -step procedures that are the hallmark of the left hemisphere's way of paying attention.

The microbiologist Brian Ford summarized the difference perfectly.

He said that equating these rich digital serial operations with the infinite subtlety of life is absurd.

And he's right.

Human intelligence, the intelligence of living systems, operates on informational input that is essentially gestalt and not digital.

Let's expand on that term, gestalt.

It means the whole, right?

The whole, yeah.

Seeing the integrated pattern, the context, the relationships all at once, simultaneously.

Living systems construct conceptual structures out of non -digital interactions, out of the context and flow.

Unlike the digitized binary serial processes of a computer?

Precisely.

Therefore, the overall argument really crystallizes here.

The LH mode's serial, procedural, abstracting details sequentially is inherently less intelligent and less flexible than the RH mode.

Which is gestalt, comprehensive pattern recognition, and contextual understanding.

Especially when the mind is confronted with a truly novel problem that demands insight.

Okay, so this sets up a really deep paradox.

It does.

If true intelligence group is RH dependent, and if our modern society, you know, driven by tech bureaucracy, scientific abstraction, increasingly privileges the LH mode.

Focusing on procedure, categories,

serial logic.

Then why did IQ scores rise for decades?

And now we enter the territory of the Flynn effect.

Named after James Flynn.

Who first meticulously documented this phenomenon.

Between the 1930s and the mid -1980s, IQ scores in Western countries rose significantly by about three points per decade.

Which forced psychologists to keep re -standardizing the tests just to keep the average at 100.

Exactly.

This just seems to contradict the thesis entirely.

You have a rising tide of measured intelligence in a culture that's seemingly dominated by the less intelligent hemisphere.

This is the central puzzle we have to solve.

So where do we start?

The first step in solving it is to adopt Flynn's own skepticism and question the reality of these gains.

Flynn himself argued that if we take these gains literally, they lead to an absurd conclusion.

And what's that conclusion?

Well, if the average IQ in 1900 measured against current norms was in the 50 to 70 range, it would imply that the vast majority of our great -great grandparents were, by clinical definition, mentally retarded.

Which is just not supported by any historical or observable evidence.

That's the critical point.

If there was a genuine 18 -point average gain in deep fluid intelligence over just two generations, that change would be highly visible.

You'd see it everywhere.

In conversation, problem -solving, societal complexity.

Yet when we look at contemporary evidence from other fields, non -IQ fields, the opposite seems to be true.

Indeed.

Despite the appearance of improving exam results, university lecturers began noticing a distinct decline in basic ability starting around the mid -1980s.

Exactly when the Flynn effect was peaking.

Precisely.

Specifically in STEM fields.

A major study by the Engineering Council of London in 2000, prompted by widespread university concern, documented a serious decline in students' mastery of basic math skills.

And this decline was masked by rampant grade inflation.

It was.

We saw nearly one whole grade of inflation in A -level mathematics between 1996 and 1999 alone.

The standards were just being lowered to meet the slipping ability, while the official scores looked good.

The cultural science outside of academia were also concerning.

Reports on the American college testing, the ACT standardized test,

repeatedly found that many high school graduates were entering college significantly ill -prepared for foundational coursework.

And maybe most symbolically, the simple act of deep reading was declining.

The percentage of Americans who hadn't read a single book in the last year rose from 16 % in 2013 to a staggering 27 % in 2019.

Wow.

But the most damning evidence against the validity of the Flynn gains, it comes from tests that measure true conceptual understanding, not just procedural knowledge.

And this brings us to the PJJtion educational stage assessments.

These assessments are designed to test fundamental cognitive development, whether a child has reached a stage where they can manipulate concepts abstractly and systematically.

They're far less susceptible to cultural coaching than standard IQ tests.

So let's look at a specific example, the volume and heaviness test.

Okay.

This is an indicator of science and math achievement, and it requires the child to understand the principle that volume, not perceived weight, determines water displacement.

The results are, well, they're terrifying.

Back in 1975 -76, 54 % of boys and 27 % of girls succeeded in demonstrating this conceptual understanding.

Okay, so a decent number.

Fast forward to 2003 -04, and the success rate for both sexes had plummeted to just 17%.

17%, a drop from over 50 % success among boys to 17 % in one generation.

Yeah.

That suggests something profound and negative is happening to our basic capacity for conceptual thought.

The authors of that very study admitted that these results make it difficult to believe in the validity of the year -on -year improvements reported nationally through IQ scores.

And the data gets even worse when you focus on the highest level of cognitive achievement.

It does.

On other piagetian assessments, like the equilibrium and pendulum tests, researchers confirmed a huge decimation of the top scorers.

The top scorers being those who reached the early formal level.

Yes, the capacity for systematic planning, deductive logic, abstract hypothetical thought.

And what happened to them?

Between 1975 -76 and 2006 -07, the percentage of these top -level thinkers dropped from around 20 -24 % down to 5 -11%, depending on the test.

We are talking about losing more than half of our most advanced cognitive thinkers.

We are.

These assessments are indicators of the raw engine of groove.

And this profound decline in the ability to handle fundamental abstract and systematic thought is a loud signal that whatever the Flynn effect was measuring,

it wasn't true.

Deep intelligence.

So now we come to the resolution of this paradox.

Since the mid -1990s, the curve has reversed.

Yes.

We've entered the era of the reverse Flynn effect.

Studies began reporting a continuous, measurable decline in intelligence test results that is comparable in magnitude to the original positive effect.

And this isn't just theoretical.

No.

The most reliable data comes from conscript populations, mandatory military service testing, which provides a consistent assessment across an entire mandated demographic.

Bypassing the issues of voluntary sampling.

And what does that data show?

Continuous decline.

Multiple industrialized nations, Finland, Norway, Denmark, Estonia, Britain, France, the Netherlands, Australia.

They have all documented this persistent year -on -year drop in IQ scores.

So using Finland as an example where scores had previously risen.

They declined by 2 .0 IQ points a decade from 1997 to 2009.

That is a measurable and rapid deterioration across the entire population tested.

And the UK data from 2008 echoed this.

It showed the average 14 -year -old's IQ score had dropped by more than two points since 1980.

It did.

But the most concerning finding is where that decline is concentrated.

It's not evenly distributed across the curve.

Not at all.

The decline is steepest for the upper half of the results.

For the most intelligent segment of the population, IQ scores dropped by six points.

Six points.

So the loss is actively disproportionately affecting those with high cognitive capacity.

When we combine this finding with the Piagetian results,

the decimation of the pool of formal abstract thinkers, it suggests that something is actually targeting that top level with special effect, rather than just reducing numbers proportionally.

It sounds like our society is actively eroding the cognitive abilities required for systematic high -level planning and novel problem -solving.

It's a selective pruning of the most valuable forms of intelligence.

That's a chilling thought.

It's the core conclusion.

We have two conflicting forces.

Temporary, non -Grey -related games driven by external factors, and a massive structural loss of capacity at the very top end of fluid intelligence.

So the paradox isn't that IQ rose while intelligence declined.

The paradox is that the IQ rise was never a rise in intelligence in the first place.

So we have to spend time breaking down the why.

Why did the IQ test scores inflate and why did they crash, dragging real intelligence down with them?

The key to understanding the initial Flynn effect, the rising scores, lies in extrinsic factors.

What the source calls picking the low -hanging fruit.

Exactly.

The positive gains were achieved by addressing environmental deficiencies, not by evolving better brains.

And one of the biggest factors here is the nutrition hypothesis.

Right.

The initial gains happened predominantly at the low end of the IQ distribution.

Historically, nutritional deprivation was most severe among the lowest economic groups.

So providing better, more consistent nutrition allowed those brains to function closer to their capacity.

Resulting in measurable, immediate gains for those below the mean.

And similarly,

increased educational coverage and targeted test training improved scores, again, primarily for those below the average.

But critically, as the research shows, the positive Flynn effect gains were almost entirely unrelated to G to general intelligence.

That is the bombshell finding that reframes the entire 20th century narrative.

It is.

The measured improvement in IQ was just an improvement in the ability to carry out IQ tests satisfactorily.

It had nothing to do with increasing actual deep cognitive ability.

And some data even show the positive gains were negatively correlated with G.

So while test scores went up because of better food and more schooling, the underlying engine of raw intelligence, gref, was either stagnant or, as later evidence suggests, already in decline.

Yes.

And now, conversely, the negative Flynn effect, the contemporary decline we are seeing, that does appear to load heavily on Jeff.

The real intelligence factor is suffering directly.

This complex situation is beautifully explained by Michael Woodley's concept of co -occurrence.

With the vivid image of a rising tide floating leaky boats.

Right.

So the model suggests we distinguish between two types of intelligence.

Genotypic intelligence, which is the real underlying level determined by genetic factors alone.

And that's actually been declining over the last century due to social changes.

And then phenotypic intelligence.

Which is the measured result, the interaction between those declining genes and improving environment.

Better nutrition, education, safety.

So the rising tide of environmental improvement was strong enough for a while to float all the leaky boats of declining genotypic intelligence higher on the water.

Creating the illusion of a rising average.

But there's a ceiling to extrinsic factors.

There is.

Once nutrition is optimized and basic education becomes universal, once the low -hanging fruit are gathered, the environmental gains peak.

At that point, the underlying decline in genotypic intelligence and the erosion of high cognitive culture take over.

Leading to the reverse Flynn effect we're now observing across industrialized nations.

The other and maybe more insidious factor behind this false rise is what the sources call the curse of the scientific spectacles.

Which relates directly to how the left hemisphere's procedural focus corrupted the tests themselves.

So part of the positive Flynn effect is just practice and cultural familiarity.

It is.

Retaking an IQ test usually adds about three points to your score without any change in real intelligence.

And the massive societal focus on assessment and educational coaching meant the population just became exquisitely good at the procedure of test taking.

And we see the ultimate irony in the Raven's matrices.

The abstract shape test.

Yeah, the one designed to be culturally neutral, measuring inventive, analogic, right hemisphere thinking.

The ability to find a pattern you have never seen before.

Precisely.

Yet because it became so popular, schools and test preparers began teaching systematic algorithms, a purely LH procedural approach, to solve the matrices.

So what was meant to measure spontaneous, Gestalt Insight now just measures diligence.

And the ability to follow a familiar procedure.

And that's the central flaw.

Following familiar procedures can be done by a machine and requires no intelligence.

Real intelligence is novel problem solving.

And the data shows that losses at the top end of actual cognitive capacity cannot be compensated for by sheer diligence or rote learning.

This leads us to that critical cultural shift documented by Alexander Luria, the father of neuropsychology.

His interviews with Russian peasants in the 1930s.

Flynn argues that the IQ rise reflects the increasing adoption of a particular way of thinking, the scientific spectacles.

And Luria's interviews provide a fantastic illustration of the difference between intelligence anchored in concrete reality and intelligence anchored in abstract categorization.

They do.

So when a peasant was presented with the syllogism, all bears are white, where there is always snow.

In Nevaia Zemlya, there's always snow.

What color are the bears there?

What was the response?

The peasant refused to answer the hypothetical question based on pure logic.

The peasant replied,

I have seen only black bears and I do not talk of what I have not seen.

And from the peasant's perspective, the logic is impeccable.

Absolutely.

Pure analytic logic can only tell us about the form of the argument.

It can't tell us about the facts.

Only experience can.

They privilege every day functional reality.

But by contrast, the moment IQ testing began, formal abstract categorization was privileged.

Creating a systematic bias toward the LH's specialized way of viewing the world.

So take the similarities test.

If you're asked how a pound and a yard are similar, saying they're both measures, an abstract taxonic category gets you a higher score.

Right.

But saying you can measure things with them, a functional process -based relationship gets you a lower score.

Or take dogs and rabbits.

The correct answer, the one the test wants, is to say they're both mammals.

A taxonomic category from science.

Right.

But the functional answer, which would have been obvious to the peasant, is you use dogs to hunt rabbits.

A descriptive process -based relationship anchored in reality.

This preference for taxonic categories, the abstract noun, a thing over the verbal phrase, a process, is the way science classifies the world.

It's the perfect expression of the left hemisphere's decontextualized specialized mode of attention.

And we even have neuroscientific confirmation of this LH bias.

The source references this striking case of a patient who had their right hemisphere removed.

And what happened?

That patient performed exceptionally well in the similarities test, defining objects almost exclusively by class membership, by the taxonic categories.

Completely missing the descriptive or functional relationships.

Completely.

The LH by itself is brilliant at categorization and abstraction.

So for our ancestors in 1900, whose intelligence was anchored in everyday functional reality, classifying a dog and a rabbit as mammals would have seemed.

Absurdly trivial.

A description that missed the point entirely.

But today, because we are so culturally steeped in the scientific worldview, classifying things by abstract categories seems obvious and intelligent.

So the apparent rise in IQ scores over the 20th century was largely the increasing cultural adoption of the scientific spectacle.

Today's children, growing up in a world of abstraction and media, have a less rich web of naturally embodied experience to unlearn.

So they naturally score better on tests that reward decontextualized abstract thinking.

It's a change in cultural style, not capacity.

And we see the cost of this shift when you look at the divergence between LH -favored and RH -favored subtests today.

Let's compare vocabulary, which is heavily LH -favored, with a crucial RH -dependent spatial ability test.

Okay.

Vocabulary scores increased between 1971 and 2007 by 0 .35 IQ points per year.

A steady positive Flynn effect gain.

Okay, a gain there, but what about the other one?

Contrast that with the three -dimensional cubes test, or 3DC.

It's a spatial nonverbal test highly dependent on RH processing.

This test showed a significant and persistent loss of 0 .48 points per year from 1977 to 2014.

A loss.

That divergence is critical.

It is.

LH -favored skills that rely on learned knowledge and abstract categorization are improving because of training and cultural emphasis.

But the crucial RH -dependent skills, the ability to visualize, understand context, perceive spatial relationships, are demonstrably declining.

And the rate of loss on that spatial test even accelerated after 1995, mirroring the reverse Flynn effect.

So that divergence strongly supports the central thesis.

We are sacrificing deep embodied gestalt comprehension for procedural abstract manipulation.

We're getting better at the language of science, but less capable of seeing the reality it describes.

And finally, to cap off the environmental link, recent Norwegian research on within -family changes in IQ, which is a very rigorous way to control for genetic factors, confirms the current negative trend is overwhelmingly environmental.

They found IQ scores declining by about 7 points per generation,

starting with those born about 40 years ago.

Which establishes that the large changes we see today are primarily due to the environmental factors in which children are growing up.

The extrinsic gains have peaked, and the cultural environment is now actively undermining general intelligence.

That was an immensely rich deep dive, forcing us to redefine what we even mean by intelligence.

Let's quickly summarize the key insights we've uncovered.

First, the evidence suggests that cognitive power, general intelligence G, and especially fluid intelligence G, depend preponderantly on the right hemisphere.

Which governs broad attention, context, and gestalt understanding, particularly in the most intellectually gifted individuals.

Second, the initial rise in IQ scores, the Flynn effect, was largely an increase in non -G -related test -specific skills.

Right, it was fueled by extrinsic factors like better nutrition and test coaching.

It amounted to an inflation of test scores, not a genuine rise in cognitive capacity.

Third, the subsequent decline, the reverse Lin effect, is a real decline loading heavily on G.

And it is characterized by the dramatic decimation of the pool of top -level abstract and systematic thinkers, as we saw in those tragic Piagetian test results.

And finally, this cognitive decline is intrinsically linked to a societal shift toward the scientific spectacles.

Which privileges the LH's decontextualized formal categorization and serial procedure over the RH's grounded, functional, and integrated understanding of reality.

We are culturally rewarding the less intelligent mode of cognition, and we are paying a profound price for it in terms of our raw intellectual ceiling.

The implications are vast.

We are trading procedural efficiency for deep analogic comprehension.

And the gap between knowledge, the LH, and wisdom, the RH, is widening.

So if our capacity for truly novel problem -solving and deep analogic comprehension lies primarily in the hemisphere whose embodied contextual way of seeing the world we are culturally abandoning, what kind of catastrophic, never -before -seen problems will we be genuinely unable to solve in the coming decades simply because we cannot integrate the pieces into a holistic gestalt?

That's something to chew on as you reflect on this changing cognitive landscape.

Thank you for joining us for this deep dive into the evidence and implications of how our minds are adapting, or failing to adapt, to the modern world.

We'll see you next time.