Lecture 28 - Critical Thinking about individual differences

Question 1

What are the two main questions in psychology as stated by Cronbach?

Answer 1

We observe a certain behavior X
1) How does X work?
2) Why do people differ in X?
Question 1): interested in intra-individual differences (differences within the individual) -> mechanism behind a behavior
Question 2): interested in inter-individual differences (differences between individuals) -> correlates and causes of behavior
Examples: arithmetics, antisocial behavior etc.
!!! Intra-individual differences are studied through experimental analyses !!!
!!! Inter-individual differences are studied through correlationl analysis !!!

Question 2

Example: Chess
How do the two questions apply in this case?

Answer 2

Intra-individual level: mechanism
- How does the mind of a chess player work
- (Why we build chess computers to understand how chess players think)
- study eye movements for example to find this
!!! studied through experimental analysis !!!
Inter-indvidual level: differences between players:
- amount of practice
- gender differences
!!! studied through correlational analysis !!!

Question 3

Case of Inteliigence:
What is the fundamental difference between intelligence and cognition?

Answer 3

• For cognition we ask about the general person (mechanisms of a single human being) and not inter-individual differences (experimental analysis again, ANOVA, stats etc.)
• For inter-individual differences we talk about intelligence (correlational analysis again, factor analysis, etc.)

Question 4

Very often the concepts of intra- and inter-individual are mixed up, what misconceptions does this lead to?

Answer 4

1) We think any intra-individual model is informative on inter-individual differences
- And thus that methods and instrunments at the intra-individual can be used at the inter-individual level as well, whereas in truth these instrunments and methods are unreliable at the inter-individual level

Why is 1) a misconception?
Measures for inter-individual differences require a test with high re-test reliability, but measures for intra-individual differences have low re-test reliability. So the mistake we make is using measures in experimental studies in studies of inter-individual differences, which is wrong.

2) The other way around (inter-individual results can be generalized to intra-individual differences, whereas in truth they can’t)

Question 5

Misconception 1):
What’s an example showcasing this?

Answer 5

We know how bikes are built and how they work (e.g. wheels, brakes, speeds, just push down the pedal and go, obviously etc.) [intra-individual level] but that doesn’t mean that we necessarily know the source of differences in speed for different bikes (doesn’t mean we know what Bike 1 does differently from Bike 2 and why it’s faster [inter-individual differences])

Question 6

(Other example, AUT test with a brick: No need to know, if you know the above example you’ve understood everything there is to this. In case you want to know more just ask me and I’ll explain it in 1 minute)

Question 7

Misconception 2):
What’s an example showcasing this?

Answer 7

Heritability (h^2)

Question 8

(Refreshing knowledge)
What is heritability?

Answer 8

How much of the variation seen in a certain trait within a population is due to genetic variation and not the environment: A measure of INTER-INDIVIDUAL DIFFERENCES
- If we have exactly the same environment, our differences are attributed only to our genes, h^2 = 1
- If our environments are extremely different, then h^2 apporximates 0

Question 9

Misconception 2):
How does heritability prove this misconception?

Answer 9

As said above, if we’re studying a trait such as resilience to stressors, and our environments are extremely different, then h^2 apporximates 0
If we do a heritability study though on lungs, results are very often h^2 = 0. This doesn’t mean though that genes have no role. We all have lungs and they are of course determined and shaped to a big extent by our genes. So the relationship h^2 = 0 doesn’t make sense here.
This example is to show that equations and models for inter-individual differences can’t be applied at the intra-individual level

Question 10

Misconception 2): This misconception also states then that models on inter-individual differences are not informative on mechanisms. What’s an example showcasing this?

Answer 10

Big 5. the Big 5 test is a between-person test, since it shows us how each person scores relative to others on 5 personality dimensions. Doesn’t say anything about our personality though (mechanism)
- Personality: within-person phenomenon, the mechanism
!!! If you conduct an experiment in which you give one person a personality test many times, then conduct an experiment comparing that person’s different scores for the different tests and do a factor analysis, you see that most people don’t have 5 dimensions. They usually have 1 or 3 (e.g. only Openness to Experience, or Om neuroticism and agreeableness for example)
(Wierd example, difficiult ot understand, I don’t think even the lecturer understood it, for now let’s assume this is true)

Question 11

Misconception 2):
How does Simpson’s Paradox apply in this case?

Answer 11

We tend to generalize between-person correlations to within person mechanisms, and of course this is wrong
(e.g. speed-accuracy tradeoff, between many people a positive correlation between speed and accuracy has been found, when studying it in the individual though there’s a negative correlation between the two. See deck on Simpson’s Paradox as well)

Question 12

Misconception 2):
What problems can SP lead to?

Answer 12

“Racist” Intelligence differences:
Assume we’re studying the heritability of group differences in Intelligence:
- inter-individual differences (difference between me and somebody else) in IQ scores are heritable (h^2 = 0.4 - 0.8) (found through twin studies, GWAS studies)
- There are also group differences (differences between psychology students and PPLE students for example) in IQ scores
We wrongly make the assumption that since there are group differences in IQ scores, and individual differences are heritable, that group differences are heritable as well -> Leads to belief that black people have lower IQ because of genes for example

Question 13

Models of individual differences

Question 14

Models of individual differences

What is the standard model of individual differences?

Answer 14

See image 7

Question 15

Models of individual differences

What is the phenomenon of the positive manifold?

Answer 15

In the standard model of individual differences, all manifest variables correlate (x) positively

Question 16

Models of individual differences

Who gave an explanation to this phenomenon and what was the explanation?

Answer 16

Spearman: When studying the positive manifold on IQ tests, he proposed the g-factor as the concept of mental power. This general mental power would explain positive correlations on IQ subtests

Question 17

Models of individual differences

What are some criticisms of g?

Answer 17

• No indepedent way to find and study g (we only observe it through the correlations between x1, x2, x3… etc.)
  This leads to other questions:
• Where is g in the brain?
• What is g actually?
• How does it develop?
  In other words, there’s no explanation about the mechanism behind it.

Question 18

Models of individual differences

What’s an alternative explanation for the phenomenon of the positive manifold?

Answer 18

Theory of mutualism:
The theory states that systems influence one another to develop.
This theory also explains the positive manifold
(See image 8)

Question 19

Models of individual differences

What is the formative model of individual differences?

Answer 19

See image 9

Question 20

Models of individual differences

What is the main difference between the standard and formative model of individual differences?

Answer 20

• Standard model: Only if you intervene at the θ level will you observe results
• Formative model: Only if you intervene at the x level will you observe results

Question 21

Why are there individual differences?

Question 22

Why are there individual differences?

What main theory does the existence of individual differences violate?

Answer 22

Fundamental theory of natural selection:
According to this theory, evolution should eliminate genetic variation and always choose the traits and characteristics that are helpful for our survival. So everyone should have been exactly the same, and have exactly the same beneficial traits.

Question 23

Why are there individual differences?

What discipline tries to give a reason for individual differences?

Answer 23

Evolutionary genetics (Evolutionary psychology (studies intra-individual differences) and behavioral genetics (studies inter-individual differences)

Question 24

Why are there individual differences?

What explanations for individual differences does evolutionary genetics give?

Answer 24

• Genetic Drift
• Mutation-selection balance
• Balancing selection

Question 25

Why are there individual differences?

Genetic Drift

Answer 25

When there’s no real selective advantage for a certain trait (e.g. hair color) there’s variation since evolution doesn’t improve anything specific (sometimes this explanation though is implausible)

Question 26

Why are there individual differences?

Mutation-selection balance

Answer 26

Many psychological traits depend on a large part of our genes. In a newborn baby, there will be mutations in it’s DNA (errors), and these small mutations, even though they might be very small, they might lead to change.
(We all have mutations in our DNA from our parents or what is the best for survival)

Question 27

Why are there individual differences?

Balancing Selection

Answer 27

An important concept here is frequency-dependent selection: If everybody else has certain traits, it might be beneficial for someone else, or a few other people to have other traits (e.g. assume everybody is fair and square and never cheat in anything they do in their lives, if the next person that comes about is a cheater, that person will benefit since nobody will cheat from him and others aren’t necessarily prepared well for cheaters. But if everybody was a cheater in this world, then there would be a problem)
- In other words, selection finds environments in which people can survive as subspecies in competition with others

Question 28

Why are there individual differences?

Differences in what phenomena does the concept of Mutation-selection balance explain?

Answer 28

• Intelligence
• Autism
• Schizophrenia
• Health in general

Question 29

Why are there individual differences?

Differences in what phenomena does the concept of Balanced selection explain?

Answer 29

Personality