PSY 2004 Individual Differences

1. Describe intelligence accutately

2. Discover real-life impact of individual differences in intelligence

3. Discover the aetiologies of individual differences in intelligence, including its' biological bases

intelligence: a very general capability that, amoung other things, involves that ability to: reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly, and learn from experience. Reflects a broader and deeper capability for comprehending our surroundings. 

Francis Galton (1822-1911): First to attempt to create a standardised test for rating a person's intelligence. Hypothesised that intelligence should correlate with observable traits such as relexes, muscle grip, and head size. For example, he believed that intelligence correlated with head size. Also created the concept of correlation.

Alfred Binet (1857-1911): French physician that sought to find an objective way to identify children who needed addition help. Mental age vs Chronological age. Developed the Binet-Simmon Scale.

Charles Spearman (1863-1945): Developed factor analysis of intelligence. Believed that people good at one subject were generally good across the board. He noticed that there were positive correlations between students' performance in a lot of very different subjects. He compared scholastic performance with ability to discriminate weights and pressures and from that these correlated as well.   

latent variable/factor: a variable that has been inferred through a mathematical model, as opposed to a variable that has been directly observed

g factor: summarizes positive correlations among different cognitive tasks, reflecting the fact that an individual's performance at one type of cognitive task tends to be comparable to his or her performance at other kinds of cognitive tasks

Takes around 3 to 5 hours to complete, but shorter tests have been developed. WAIS was published in 1955; the WAIS-R was published in 1981. Wechsler Bellevue test was one of the first tests that were created (released in the 1930s, revised in the 1940s). 

WISC = Wechsler Intelligence Scale for Children

WPPSI = Wechsler Preschool and Primary Scale of Intelligence 

WAIS = Wechsler Adult Intelligence Scale 

WAIS is an IQ test designed to measure intelligence and cognitive ability in adults and older adolescents. 

Developed and marketed by the Psychological Corporation. 2450 people between the ages of 16 to 89 people (1225 females; 1225 males) from the USA were tested for the WAIS-III. The ethnic and regional mix was reflective of USA population; there was a good spread of educational backgrounds. Every person sat the 13 tests that make up the WAIS-III.

Substantial correlations between scores were observed on all of the takes. All 78 correlations were all significant, the lowest being 0.3 and the highest being 0.8. So, full-scale IQ or the best estimate of g, is a weighted average of all of the correlations. 

IQ scores are standardised to have a mean of 100 and a SD of 15. So, an IQ of 100 from 50 years ago would be different from an IQ of 100 now. 

The more tasks you average across, the closer you get to an estimate of g itself. Some tasks are more g-loaded than others (as in, they correlate more highly with the average across all tasks). 

FSIQ - 1. Verbal IQ (VIQ) 2. Performance IQ (PIQ)

1. VIQ → Verbal Comprehension Index (VCI) + Working Memory Index (WMI)

2. PIQ → Perceptual Organisation Index (POI) + Processing Speed Index (PSI)

• Not all intelligence tasks correlate equally highly
• There appears to be group gactors that apply to sets of tasks
• Group factors were traditionally identified as verbal and non-verbal/performance
• The FSIQ factors are NOT ONTOGONAL

• The combination of g and group factor is not enough to account for how well people perform on the individual tests
• s factor: specific ability needed to do well on each test, something that is not shared with any other test even where the material in the test is quite similar to that in other tests
• Spearman argues that the pattern of performance on all the tasks can be explained as:
  • Performance = s + g
    • where s is a factor specific to the task and g is a general intelligence factor 

All five factors/domains have high correlations with g.

Nerve conduction velocity - measured by applying a burst of current through the skin over a nerve and picking up its time of arrival further up or down the nerve, good correlations with IQ

Inspection time (IT) - You see a pattern for a very short period of time (50ms or less), followed immediately by a mask. You must identify it as one of two possible shapes. High IQ participants are faster at this task. 

If you restrict analysis to people at the high end of the spectrum, the intercorrelations are very reduced (to about 0.3). If you restrict analysis to people at the lower end, correlations increase to about 0.6. 

Therefore, the unity of g is influenced by some people not doing very well at any task. 

Approach:  The effects of cognitive and non-cognitive individual differences on the dynamics of career success (i.e. pay, occupational status) by comparing temporal changes in the validities of two measures of personality--Core Self Evaluations and the Big Five personality dimensions--to temporal changes in the validities of two standard intelligence tests. 

Methods: Pearson correlation, standard regression, heirarchical linear modelling

Findings: Found significant main effects of personality characteristics on career success. However, only from the main effect perspective is this consistent with the hypothesis that personality is an antecedent of career success. When long-term prediction is called for, the usefulness of intelligence-based predictores surpass that of non-cognitive predictors. 

(Ganzach and Pazy, 2015)

fluid intelligence (gf): described as 'intelligence-as-process'. It is typically assessed using tests that require on-the-spot processing; WMI, POI, PSI. Declines during late adulthood. 

crystallized intelligence (gc): 'intelligence-as-product'. It is typically measured using tests that assess stored knowledge, such as vocabulary and general facts; VCI

Factors such as having good health, living in a favourable environment mediated by high social class, etc help retain mental abilites as we grow older. 

Clever childer tend to be clever adults: people who did well in 1932 also tended to do well in 1998. The correlation was high (>0.6; with more recent estimates suggesting that this corrrelation may actually be as high as 0.7).

However, perfect stability was not observed.

There are many brain regions whose size/grey matter density are associated with IQ. Studies have also found that there is a correlation between in vivo brain volume and IQ. Brain glucose activity studied through PET has a negative correlation between glucos metabolic rate and Raven's matrices scores (abstract reasoning and attention). There are also good correlations between brain connectivty and intelligence. 

However, anything likely to reflect a higher quality development trajectory will be correlated with intelligence. 

Intelligence is also associated with body symmetry. The quality of development can predict that the existence of g will be main due to some individuals not being so good at any cognitive tasks. It predicts both environmental inputs and genetic mutation load should be important for intelligence. It also predicts that lower intelligence should be associated with reduced longevity and other vital outcomes. 

Intelligence is related to longevity - Study of 1 million Swedish men. Every SD increase in IQ is associated with 32% decrease in mortality risk 20 years later.

Breastfeeding duration and adult IQ - Breastfeeding alone producted better brain development than a combination of breastfeeding and formula, which produced better development than formula alone. Breastfed children showed improved receptive language scores relative to the formula-fed children. 

Low birthweight and IQ in early adolescence - Low birthweight reflects sub-optimal birth environment. Low birthweight people had a IQ one SD below the mean.

General anesthesia in early childhood and IQ - Anesthesia is neurotoxic to developming brain

Chemotherapy in childhood an IQ - affects verbal and visual memory as well as IQ, survivors did worse than test norms.

Many aspects of brain functioning including overall brain size, connectivity, and efficiency are correlated with intelligence.

Intelligence is also correlated with body symmetry, suggesting it is related in a general way to quality of development.

This may explain why intelligence is sensitive to multiple environmental and genetic influences.

This also explains why intelligence is associated with other development-sensitive parameters such as health and longevity.

g is the common factor arising from the inter-correlation of performance on many different cognitive tasks.

The array of tasks is too broad for g to be considered a measure of 'book smarts' or any particular cognitive ability--more like a general measure of nervous system efficiency. 

The unity of g is influenced by the fact that some individuals are not so good at any task.

Heredity - IQ has a genetic component 

Nurture - IQ is transmitted by nurture and high IQ parents transmit high IQ by the way they nurture their children

Shared Environment - There is some environmental factor that determines variation in IQ that tends to be shared within families

Some combination of the above is a possible explanation of IQ.

Study

Monozygotic twins reared together. 4672 pains in 34 studies. If IQ is genetic, the expected correlation should equal 1.00. The actual correlation was between 0.58 and 0.9 and the weighted average was 0.86.

Dizygotic twins reared together. 992 pairs in 8 studies. If IQ is genetic, the expected correlation should equal 0.50. The actual correlation was between 0.21 and 0.8 and the weighted average was 0.60.

Adoptive parent-adopted child correlation was around 0.19.

Monozygotic twins reared apart. 65 pairs in 3 studies. If IQ is genetic the expected correlation should equal 1.00. The actual correlation was between 0.62 and 0.75. The weighted average was 0.72.

Researchers study the way characteristics assort in families (e.g. monozygotic vs. dizygotic twins) to make estimates of the heritability of the characteristic.
Heritability is a number between 0 and 1, like a correlation.
Heritability denotes the proportion of variation in the characteristic that is associated with variation in genetic material.

Heritability is either increasing because genetics are contributing more to the geners or because non-genetic factors, such as environment, is contributing less. 

Heritability: the percentage of variation of traits due to genes and is very dependent on the population and environment that is studied

A number of studies converge on the view that in contemporary Western populations about 50% of the variation in IQ is heritable, and about 20% associated with variation in the home environment.

The heritability of IQ is therefore about 0.5.

In westernised industrial societies, the heritability of IQ general increases as we age.

There are many argument and mostly controversial concerns on group differences. In the USA, African Americans score around 15 points lower on average than White Americans. Also lower education, economic achievement, etc affects IQ. 

Also varies acroos social groups. As socioeconomic status increases, heritability goes up and contribution of the environment goes down.

This argument hypothesizes that African Americans have lower IQ scores. IQ is highly heritable. Therefore, the lower attainment of African Americans is due to genetic differences between the races. This argument is wrong! Say, African Americans and White Americans start off with equal genes and equal potential. White Americans are more likely to have favourable conditions due to better schools, social status, etc compared to African Americans. Therefore, the differences between the two races is due to the environment. Differences in heritability can only be compared within a group. Heritability increases as the homogeneity of the environment increases – homogenous environment leads to high heritability.
And, although heritability can tell you about the sources of variation within a population, it cannot tell you anything about variation between populations.

This model assumes that high intelligence reflects all the developmental factors through which the brain is developed. 

High intelligence is due to large and efficient brains with good connectivity, fast inspection times, and fast nerve conduction. 

Anything likely to reflect a higher quality developmental trajectory will be correlated with intelligence. 

There are about 300 known genetic mutations associated with mental retardation.
Genome-wide association studies have not found common variants that explain much of the genetic variance in IQ across normal range (‘problem of the missing heritability’).
Suggests mutations of small effect in many genes.
Not surprising if intelligence represents optimality of developmental trajectory.

IQ has a heritability of about 0.5 within affluent populations. However, the heritability is lower in deprived social groups. GWAS studies suggest many mutations of small effect is most likely genetic architecture. Heritability within populations does not explain differences between groups. These are likely to be environmental and reflect quality of developmental environment of different social groups.

We standardise IQ because IQ keeps increaseing over time and very quickly. The greatest gains in intelligence is in fluid intelligence due to the Flynn Effect. 

We see a greater increase with the Raven Matrices (tests fluid intelligence) compared with the Weschsler and Stanford-Binet tests. Therefore it's not that we know more now, it is that our processing speeds have increase. 

The Flynn Effect is the phenomenon in which there is a marked increase in intelligence test score averages over time. This has been reported to happen worldwide. Intelligence testing began in the 1930s and the average scores have steadily increased since then. Intelligence tests are standardized at a score of 100 which means that 100 is the average score of all who take it. 

When a test is revised they are standardized to a score of 100 again so that it is certain they are measuring correctly in relation to the new group of test takers. When a new group of people take the previous test there is an increase in scores with the new group typically scoring well above 100 (which is the average).

There are many possible explanations for the Flynn Effect including better nutrition, less infectious disease, longer and more productive education, and more stimulating environments.

Evidence from Norwegian and Kenya studies

These studies show correlations that improved environment and situations will lead to improved IQ. Remember, this is not a causation. 

IQ scores in developing countries are increaing faster than developed countries. Consistency may be due to the fact that devloped countries have consistent levels of health, economy, etc. Countries having more changes show more IQ changes. 

The Flynn effect was investigated in 734 samples and 202,468 total participants from 48 countries, covering a period of 64 years.

A relationship was found between RPM mean scores and year of publication (the Flynn effect), moderated by sample age grouping and country type.

Participants in developed countries had higher scores, but IQ gain over time was much larger in developing countries.

It cannot be due to genetic change. The debate is mainly between 'cultural' explanations and mainly 'material' ones. It is not to do with knowledge transmission or teaching, as the greatest increase is in fluid intelligence. It could be to do with practices or valuation of abstract reasoning.

Material explanations are supported by close associations with height, nutrition, etc. Effects are also very large. The average person today would be considered a genius in 1950, and the average person from 1950 more or less educationally subnormal, on Raven's Matrices. 

There is a significant decline of overall IQ in developed countries. 

Given the much greater number of ‘geniuses’ around today, we should expect flowering of the arts, sciences and innovation that by most accounts we have not seen.
Flynn suggests that this is because fluid IQ tests measure something only loosely related to what we would call ‘intelligence’ in actual life.
Another way of saying this is that high intelligence is a necessary condition for innovation and success, but not a sufficient one.

Given the much greater number of ‘geniuses’ around today, we should expect flowering of the arts, sciences and innovation that by most accounts we have not seen.
Flynn suggests that this is because fluid IQ tests measure something only loosely related to what we would call ‘intelligence’ in actual life.
Another way of saying this is that high intelligence is a necessary condition for innovation and success, but not a sufficient one.

A nonverbal group test typically used in educational settings. It is usually a 60-item test used in measuring abstract reasoning and regarded as a non-verbal estimate of fluid intelligence. 

This format is designed to measure the test taker's reasoning ability, the eductive ("meaning-making") component of Spearman's g (g is often referred to as general intelligence). 

trait: An observable characteristic. A dimension of peronality used to categorise people accodring to the degree to which they manifest a particular characteristic. The 'conditional' probability of a category of behaviours in a category of contexts. We retain traits in all contexts.

• Always continuous (not introverts vs extroverts etc)
• Everyone has a value for eary trait and it is usually in the middle. 
• In this context, trait, dimension, factor, and construct is roughly equivalent in this context. 

The five-factor model: Personality variation is continuous and occurs on five principal orthogonal axes. The five axes are Openness, Conscientiousness, Extraversion, Agreeableness, and Neuroticism. 

• orthogonal: (of variates) statistically independent 
• Data-driven and atheoretical in origin
• Arises from factor analysis of ratings
  • factor analysis: Identifies attributes that cluster together. Cluster are composed of items that correlate with each other. In SPSS, dimension reduction, orthogonal = varimax. 

History

• 1980s - Goldberg: FFM is a generally comprehensive taxonomy 
• 1990s - Costa and McCrae: All other taxonomies can be mapped to FFM
• 2000s: Consensus framwork for trait psychology 
  • Eysenck - Psychoticism related to Agreeableness, conscientiousness, and openness 
  • Tellegan/Watson & Clark (known for PANAS) - Positive emotion = Extraversion, Negative emotion = neuroticism, Constraint = Conscientiousness 
  • Myers-Briggs - Extraversion vs Introversion, Agreeableness = Feeling vs Thinking, Conscientiousness = Judging vs Perception, Openness = Intuition vs Sensing

The BFI is stable over the lifespan and acroos cultures. 

Intracranial self-stimulation is the basis of reward. In self-stimulation, dopamine is released. Dopamine is produced in the VTA. The VTA sends dopamine to the amygdala, nucleus accumbens, prefrontal cortex, and hippocampus. Cocaine increases dopamine levels.

Mid-brain hypothesis — Extroverts have a more active system » pleasure from being extroverted/social.

• Extroverts have a boost from positive mood whilst introverts stay the same

High-thrill sports, interest in sex/sexual partners, smiling/positive emotions, sociability, interest in fame, competiviteness/ambition, and salary are all correlates of extraversion. 

This suggests that the core of these is response of positive emotion and reward systems. 

However, there is no direct evidence but the circumstantial case is strong. 

Health, stress and hassles, relationship dissatisfaction, self-esteem, worry, anxiety disorders, and depression are correlates of neuroticism. 

This suggests that the core of these are the response of NEGATIVE emotion systems. 

High neuroticism is associated with: 

• Increased performance amongst university students high in ego control
• Success in professional (‘thinking’) occupations 
• Fewer accidents in adulthood
• Not doing dangerous stuff:
  • Everest Climbers are low on Neuroticism whilst guides are high on neuroticism

May also interact with intelligence » High neuroticism and low cognitive abilities = more sick days

Contextual fear conditioning: Fear, not only by the stimulus, but the context surrounding it as well. 

It involves the hippocampus. It receives affective impulses from the amygdala and integrated with previously existing information to make it meaningful. 

Patient S.M. had the inabiilty to feel fear due to a genetic condition, Urbach-Wiethe disease, which lead to the calcification of the amydgala.

S.M. had basic instinct to save self-preservation, however S.M. had loss fear in social situations and did not learn from dangerous situations.

S.M. lacked negative surprise and could not recognise fear expressions. 

Structural differences

Amygdala and depression » larger amygdala

Dysthymia and amygdala volume » large amygdala volume is asociated with dysthymia 

Functional difference

Findings suggest that there is a close relationship between psychiatric symptoms and an exaggerated amydala response to emotional material e.g. Depression, Phobias, Borderline personality disorder, PTSD. So, the amydgala is a core structure of emotional processing. 

Amygdala activation is positively correlated with self-reported anxiety and PTSD symptom severity. 

Amygdala hyper-responsivity in PTSD has been reported during the presentation of personalised trauma, traumatic narratives, combat sounds and photographs, and trauma-related words and trauma-unrelated affective material. 

Serotonin is expressed in the amygdala. It is the target of several classes of anti-depressant drugs i.e. MOAIs, SSRIs.

MDMA also works on the serotonin pathway and it supresses the emotion system. 

Monkeys with high neuroticism have more serotonin transporters available in the amygdala. 

High neuroticism with negative mood induction = negative mood change

In the traditional “fear centre” model, the subjective experience of “fear” in the presence of a threat is innately programmed in subcortical circuits that also control defensive behaviors and physiological responses. The traditional view thus requires different mechanisms of consciousness in the brain for emotional and nonemotional states.

Threat » Sensory system » FEAR » Fear reponses 

Fear responses: Defensive behaviour, physiological responses i.e. freezing, facial expressions, flight, avoidance, changes in heart rate, BP, and other autonomic nervous system adjustments

Circuits underlying defensive reactions and actions

The amygdala is the central hub of circuits that control reactions and actions elicited by an immediately present threat. The lateral amygdala (LA) receives sensory inputs about the threat. Connections from LA to the central nucleus of the amygdala (CeA) control reactions, whereas connections from LA to the basal nucleus (BA), and from there to the ventral striatum (nucleus accumbens, NAcc), control the performance of actions, such as escape and avoidance.

• Defensive reactions » amygdala. Defensive actions » Striatum

But more recently, a number of studies have pointed to the bed nucleus of the stria terminalis (BNST) as a critical area in the mediation of trait anxious temperaments. 

• Uncertain threat is processed through the BNST (Extended amygdala)

Humans in fMRI, looking at the functinos of the brian. If they look at lines, they wil get shocks in the future. 

BNST: tracking, very active in high neuroticism and anxious people 

The amygdala does not do much in future fear/threat. 

The left BNST may be related to hypervigilance. 

(Somerville, Whalen, Kelley)

Mouse study

BNST mediates variation in anxiety and fear. Rats generalised to non-conditioned tone lead to over-generalisation. 

When the BNST was legioned, the mice did not generalise the second tone. 

(Duvari, Baver, Paré) 

The amygdala is not itself responsible for the experience of fear. Its job can be more appropriately viewed as detecting and responding to present or imminent threats. The amygdala contributes to fear indirectly but is not an innate fear center out of which fear percolates.
And the BNST is not itself responsible for the experience of anxiety, but instead is a key part of an innate defense circuit that detects and processes uncertain threats.

The BNST contributes to anxiety indirectly in the way that the amygdala contributes indirectly to fear — consequences of its activation generate signals that modulate circuits that are directly responsible for subjective feelings of fear and anxiety.

The amydala is not itself responsible for the experience of fear; its role should be viewed as detecting and responding to present or immient threats. Fear or anxiety are not products of subcortical circuits underlying defensive responses, but they depend n the same circuits that underlie any other form of conscious experience.  

Two-system framework gives a way to understand what animal research can and cannot tell us about human fear and anxiety without making the impossible assumption of what animals equate human feelings of fear and anxiety. Being clearer about feelings of fear and anxiety, versus research defensive behaviour and physiological responses, should enhance the translational impact of animal research.

Current approaches fail to recognise adequately the distinctions between neural circuitry supporting subjective feeling states as opposed to defensive responding. A conceptual reframing is needed for fear and anxiety. LeDoux and Pine (2016) propose a two-system view. With this new framework, more effective pharmaceutical and psychological treatments can be developed.

Fear: describe feelings that occur when the source of harm, the threat, is either immediate or imminent

Anxiety: describe feelings that occur when the source of harm is uncertain or distal in space or time