Lecture 2

Question 1

Tiedmann (1836)

Answer 1

There exists “an indisputable connection between the size of the brain and the mental energy displayed by the individual man”

Question 2

Head size vs intelligence

Answer 2

• Vernon et al (2000) – Population correlation between head size and intelligence is 0.19.
• Nguyen and McDaniel (2000) – Population correlations from 0.17 to 0.26 (different sub categories of external head size measures).

Question 3

Brain volume vs intelligence

Answer 3

• Vernon et al (2000) – Population correlation between brain volume and intelligence is 0.33
• Nguyen and McDaniel (2000) – Population correlations is 0.33
• Gignac, Vernon and Wickett (2003) – Mean correlation is 0.37

Question 4

McDaniel (2005) Meta-analysis Findings

Answer 4

Significant weak positive correlation (between 0.3-0.4). Stronger correlation for females.

Question 5

Pietschnig et al (2015)

Answer 5

Reviewed published and unpublished studies of over 8000 individuals. Significant positive correlation of 0.24 between brain volume and IQ.

Evidence of publication bias for studies that show strong positive correlations.

Question 6

Grey matter definition

Answer 6

Consists of neuronal cell bodies

Question 7

Cortical thickness definition

Answer 7

The thickness of the brain’s grey matter

Question 8

White matter definition

Answer 8

The connecting network of axons (or ‘wires’) in the brain

Question 9

White matter integrity definition

Answer 9

A measure of the health of the white matter connections

Question 10

White matter hyperintensities definition

Answer 10

Scars in the brain connections

Question 11

2019 UK Biobank Study (Cox et al, 2019) participants

Answer 11

29004 overall
18426 providing MRI and at least one cognitive test
Mean age 63 years

Question 12

Cox et al (2019) correlations

Answer 12

Total brain volume - 0.276
Cortical thickness - 0.24
White matter integrity - 0.24
White matter hyperintensities – -0.2 (high IQ means fewer white matter hyperintensities)

Question 13

Cox et al (2019) results

Answer 13

Grey and white matter amount for more than double the g variance in older participants compared to younger

No sex differences

The largest brain regions that affected intelligence were insula, frontal, anterior/superior, medial temporal, posterior and paracingulate, lateral occipital cortices, thalamic volume, the white matter microstructure of thalamic and association fibres, and of the forceps minor.

Question 14

Pietschnig et al (2015) quote

Answer 14

“While it is tempting to interpret this association in the context of human cognitive evolution and species differences in brain size and cognitive ability, we show that it is not warranted to interpret brain size as an isomorphic proxy of human intelligence differences.”

Question 15

Songthawornpong et al (2021)

Answer 15

50 brains from Danish males (aged 20-52 years) for whom there was documentation of premorbid IQ (mean 94, SD 14)
IQ does not correlate with the number of brain cells in the human neocortex and was only weakly correlated to brain weight.

Question 16

Neurons definition

Answer 16

The basic working units of the brain. They transmit information via electrical impulses to other nerve cells, muscles or gland cells

Question 17

Oligodendrocytes definition

Answer 17

Lay down myelin around some, but not all, axons. Myelin sheets accelerate the transmission of electrical signals along the neurons axon.

Question 18

Astrocytes definition

Answer 18

Maintain an appropriate chemical environment for neuronal signalling

Question 19

Microglial cells definition

Answer 19

Scavenger cells that remove cellular debris from sites of injury or normal cell turnover. Following brain damage, the number of microglial at the site of injury increases dramatically.

Question 20

Kabadayi et al (2016) animal studies results

Answer 20

The Corvus species performed on a similar level to the great apes, despite vastly smaller absolute brain sizes.

A chimpanzee brain is roughly 26 times larger than a raven’s, but both species achieve 100% success.

The jackdaws were more successful than either the bonobos or gorillas, despite a brain 70-94 times smaller.

Absolute brain size is no overall predictor of motor self-regulation across a wider range of animal taxa.

Question 21

Scholz et al (2009)

Answer 21

48 healthy adults, 24 control.

Other 24 underwent juggling sessions for 6 weeks for 20 minutes. White matter in the brain changed.

Question 22

Maguire et al (2000)

Answer 22

Correlation of volume change with time as a taxi driver

Question 23

Haier et al (1988)

Answer 23

Negative correlation between glucose metabolic rate and intelligence score using Raven’s matrices.

Question 24

Haier et al (1992a)

Answer 24

After learning a complex visuo-spacial task there was decreased cerebral metabolism

Question 25

Haier et al (1992b)

Answer 25

After learning to play tennis there were decreases in cerebral metabolism in higher IQ participants.

Question 26

Ruigrok et al (2014)

Answer 26

On average, adult male brains have 10.8% larger total brain volume than women

Question 27

(Dyliert et al, 2009; Flynn, 2012; Johnson et al, 2009)

Answer 27

There is an absence of sex differences when it comes to intelligence

Question 28

Haier and Benbow (1995)

Answer 28

• 22 male and 22 female participants
Half of the males and half of the females had high SAT-Maths Scores (collect entrance; >700)
The other half had average SAT-Maths Scores (410-540)
• During the PET scan, each participant completed a new SAT-Maths test
• Male Participants: significant correlations between the math score and glucose metabolism in the temporal lobes bilaterally (middle, inferior, and posterior; analogous to Bas 20, 21, 22)
• Female participants: no correlations

Question 29

Cultural differences

Answer 29

Gross Domestic Product (GDP) was significantly correlated with spatial-visual intelligence in a video game created by UCL to help with dementia research.

Question 30

Ryman et al (2016) - White matter efficiency differences

Answer 30

In male participants: no correlation with IQ

In female participants: positive correlation with IQ

Question 31

Ryman et al (2016) - Grey matter differences

Answer 31

In male participants: a significant positive relationship between fronto-parietal grey matter region volumes and intelligence.

In female participants: total grey matter volume did predict intelligence in females, but regionally specific contribution of the fronto-parietal gray matter volume was not evident.

Question 32

Finn et al (2015)

Answer 32

fMRI obtained from 126 participants. Connectivity was stable across all conditions but are unique to individuals.

Question 33

Finn et al (2015) quote.

Answer 33

“functional connectivity profiles act as a ‘fingerprint’ that can accurately identify subjects from a large group”

“connectivity profiles … that were most discriminating of individuals were also most predictive of cognitive behaviour”

Question 34

Miranda-Dominguez et al (2014)

Answer 34

A given brain region can be described by the weighted sum of its functional neighbouring regions. (Brains have a different way of showing intelligence for each different person).

Question 35

Miranda-Dominguez et al (2018)

Answer 35

Individual intelligence is genetic and most heritable systems include the fronto-parietal, dorsal attention, ventrical attention, cingulo-opercular and default systems.