2019-06-22_New_Scientist

22 June 2019 | New Scientist | 37

Think about thinking, and it doesn’t take

long for your mind to go down a rabbit

hole. Thoughts come naturally to us, but

pinning down exactly what they are is

more complicated. Once they were viewed

as immaterial entities, separate from the

biological matter of the brain. Now we know

that our every thought – whether about a

simple object or an abstract idea – is the

result of electrical signals pulsing through

the brain’s network of 86 billion neurons.

“For me, a thought is simply the

transformation of inputs to outputs by

the brain,” says Ethan Solomon at the

University of Pennsylvania.

But if you ask 100 neuroscientists for a

definition, you will get 100 different answers,

says Avgusta Shestyuk at the University of

California, Berkeley. “‘Thinking’ is an umbrella

term that covers multiple different cognitive

processes,” she says. Some thoughts take the

form of pictures, others seem to be comprised

of words, and many take place at the

unconscious level, without us even noticing.

The latest neurological studies let us tune

into the electrical signals that underlie

thinking. They show that even a basic

kilometres of

nerve fibres

850,000

The short answer is yes. People vary in
their intelligence, so how else could we
account for this if not for differences in the
structure or function of the brain? Exactly
what those differences are, however, is a
matter of intense investigation.
The first thing to note is that people with
larger brains really do tend to have higher
IQs, but there is more to this than size (see
“What makes our brain special?”, page 34).
To find out more, we need to zoom into the
white and grey matter that makes up our
brain. The latter is comprised of the main
bodies of neurons, whereas white matter
is made of the fibres down which they send
signals. Rogier Kievit at the MRC Cognition
and Brain Sciences Unit in Cambridge, UK,
and his colleagues have found that the
volume of grey matter in the frontal lobe
(see diagram, right) is connected to fluid
intelligence, which is the ability to solve
novel problems. They also found this
was linked to the amount of white matter
connections between the two halves of
the prefrontal part of the brain.
It isn’t just the amount of tissue that
counts. One of the most striking features
of the mammalian brain is the way it has
deep folds of grey matter on its surface,
giving it a walnut-like appearance. These
increase its surface area, bringing cells
closer together and allowing them to
communicate faster. And sure enough,
the extent of the folding is correlated with
speed of thought and working memory:
smarter people have more-folded brains.
But this still doesn’t tell us where in the
brain intelligence resides. To find this out,
we can turn to one of the most popular
ideas about its location, something called
parieto-frontal integration theory. This
proposes that the biological basis of
intelligence is a network connecting
different brain hotspots.
Clues about these hotspots can be found
in brain-imaging studies. By examining
how parts of the brain became activated
during cognitive tasks, Ulrike Basten at
Goethe University Frankfurt in Germany
and her colleagues identified a network
connecting 20 different areas in the frontal
and parietal regions that were associated
with intelligence. People with more grey
matter or higher neural activity in these
regions were smarter.
It feels like we are getting somewhere,
but that result doesn’t just mean that

smarter people have physically different

brains: they seem to have ones that work

more efficiently too. A brain might have the

right chassis for high performance, says

Emiliano Santarnecchi of Harvard Medical

School, “but it’s not that relevant without

an on-board computer regulating how

power is delivered and when to allocate

resources at any given moment”.

Santarnecchi’s work suggests

that intelligence can be boosted by

magnetic stimulation to increase the

brain’s processing efficiency. He also

emphasises the importance of plasticity,

or the ability to change. Perhaps some

people’s brains are inherently more

plastic, more capable of learning.

This is to say nothing of genetics.

Although we know that hundreds of

genes contribute to intelligence, it

is going to take a long time to discover

the nuances of their impact. But then it

was never going to be a simple matter

to find the location of intelligence, the

richest human trait, in the brain, the most

complex known object in the universe. RH

What happens

when we think?

Are smarter people’s

brains different?

Alpha brainwaves >

Visual cortex

Occipital lobe

Visual processing

Auditory cortex

Hippocampus

Know your brain

The human brain operates using specialised processing units

BOTTOM BRAIN

Classifies and

interprets information

TOP BRAIN

Creates and

monitors plans

Frontal lobe

Prefrontal

cortex

Motor cortex

Problem-solving, complex

thinking, decisions

Planning

complex

behaviour

Planning and

executing movement

Integration of sensory

information, perception

Parietal lobe

Language, hearing,

processing sensory

information into memories

Memory

Temporal lobe

SOURCE: AI IMPACTS