Week 1 & 2

Question 1

Define differential psychology

Answer 1

Individual differences are the more-or-less enduring psychological characteristics that distinguish one person from another and thus help to define each person’s individuality. Among the most important kinds of individual differences are intelligence, personality traits, and values.

Question 2

The concept of personality has been studied for at least 2000 years starting with Hippocrates (460-370BC). Describe Hippocrates personality theory

Answer 2

Hippocrates theorised that personality traits and human behaviours are based on four separate temperaments associated with four fluids (“humors”) of the body: choleric temperament (yellow bile from the liver), melancholic temperament (black bile from the kidneys), sanguine temperament (red blood from the heart), and phlegmatic temperament (white phlegm from the lungs) (Clark & Watson, 2008; Eysenck & Eysenck, 1985; Lecci & Magnavita, 2013; Noga, 2007).

Question 3

Describe how Roman physician and philosopher Galen developed Hippocrates four humors theory

Answer 3

He suggested that both diseases and personality differences could be explained by imbalances in the humors and that each person exhibits one of the four temperaments. For example, the choleric person is passionate, ambitious, and bold; the melancholic person is reserved, anxious, and unhappy; the sanguine person is joyful, eager, and optimistic; and the phlegmatic person is calm, reliable, and thoughtful (Clark & Watson, 2008; Stelmack & Stalikas, 1991). Galen’s theory was prevalent for over 1,000 years and continued to be popular through the Middle Ages.

Question 4

What are implicit personality theories?

Answer 4

These are intrusively based theories of human behaviour that we all construct to help us to understand both ourselves and others. We hear descriptions of individuals and we observe people going about their business, chatting with us and with others, and then we use this information to help us decide what sort of person we think they are. Most of the time we are not even consciously aware that we are doing this; it happens so frequently that it becomes an automatic response. We use our observations to construct our implicit personality theories. These implicit theories are then used to explain behaviour. For example, what about the student in your seminar group who never contributes to the discussion? Is it because of shyness, stupidity or laziness? How would you decide? 4 Part 1 Personality and individual differences We make observations and then we infer cause and effect.

Question 5

Detail some problems with implicit theories

Answer 5

Implicit theories appear to work well, but a major difficulty with them is that we seldom have the opportunity to check them out properly. If it turns out that we get along well with Sarah as a flatmate, we congratulate ourselves on being a good judge of character. Joanne might have been even better, but we will never know. In this way, our evaluation of the situation is flawed.

Implicit theories are also based on casual and nonrandom observations of individuals. By this, we mean that they are not based on observations of behaviour that have been systematically selected to portray accurately how that person spends his or her life. Instead, we have chance observations of other people. With most people, we sample only a tiny fraction of their behaviour; yet, based on this, we have to make decisions about whether we are going to pursue a friendship with them, give them a job or go out of our way to avoid them in future. If we decide not to pursue further contact with the individual, that is usually the end of the story.

Implicit theories are not scientific theories of personality.

Question 6

Describe the problem with defining personality

Answer 6

Psychologists need to be very clear about exactly what they are studying and define it precisely if they are going to measure it effectively. One difficulty that frequently arises is that many of the words used by psychologists are already part of our everyday language or have been adopted into normal language use. However, it is still important to consider what the public (as opposed to psychologists) think that a term means so that accurate communication can occur.

Question 7

What are lay definitions?

Answer 7

In most instances public, or lay, definitions tend to be very wide and not specific enough for psychologists to use for research purposes to define precisely what they are examining. However, lay definitions provide a good starting point for developing psychological definitions.

Question 8

Describe lay definitions of personality

Answer 8

Lay definitions of personality frequently involve value judgements in terms of the social attractiveness of individuals. Sometimes the emphasis is on aspects of the individual’s physical appearance, perhaps with some comments on their social style. These lay definitions are commonly linked to the implicit personality theories that we discussed earlier.

Sometimes they include elements of folklore within particular cultures. This may be an assumed match between a physical attribute and a personality attribute. Common examples are that people with red hair also have fiery tempers or that fat people are jolly.

Does this mean that our personality is apparent only in social situations? This is obviously not the case. When people are alone, they still display individual differences in terms of how they cope with solitude and their attitude towards it. For most people their personality is an integral part of their being, which exists whether they are alone or with others.

Question 9

Describe the difference between psychological and lay definitions of personality

Answer 9

Psychological definitions of personality differ from lay definitions in that they define personality in terms of characteristics, or the qualities typical of that individual.

Question 10

How did Gordon Allport (1961) define personality?

Answer 10

Gordon Allport found over 18,000 separate terms where individual differences are possible, where 4500 appeared to describe aspects of personality.

Whilst some of these are common traits (that could be investigated nomothetically) the majority, in Allport’s view, referred to more or less unique dispositions based on life experiences peculiar to ourselves.

He argues that they cannot be effectively studied using standardised tests. What is needed is a way of investigating them idiographically.

He defined personality as ‘a dynamic organisation, inside the person, of psychophysical systems that create the person’s characteristic patterns of behaviour, thoughts and feelings’ (Allport, 1961, p. 11).

Question 11

History of defining personality

Answer 11

The word ‘personality’ derives from the Latin persona, meaning ‘mask’ (Kassin, 2003).

Prior to this a variety of terms, such as ‘character’ or ‘temperament’, were commonly used. Allport carried out a survey of the ways in which the concept of personality has been defined; he identified over 50 different ways. These varied from lay commonsense understandings to sociological, philosophical, ethical and legal definitions. Allport argued that many of the existing terms were value-laden in the way that they were used. Examples would be a description of a woman of good character or a man of bad character. Within a particular cultural setting, this description would take on a specific meaning that was generally shared. Allport felt it was necessary to develop a consensus on the use of a word that would describe individual uniqueness without implying an evaluation of that uniqueness. As a result of Allport’s influence, ‘personality’ increasingly became the term used across the discipline to describe individual differences.

Question 12

What is the idiographic approach?

Answer 12

The idiographic approach is concerned with the uniqueness of the individual.

Question 13

What is the nomothetic approach?

Answer 13

The nomothetic approach attempts to study human behaviour through the development of general principles and universal laws.

Question 14

Detail the nomothetic approach

Answer 14

• Fixed set of variables that can be used to describe human personality (Greek: ‘law’).
• Study of large groups of people to establish averages, or ‘norms’.
• Focus on similarities.
• Primarily studied using quantitative methods
• E.g., questionnaires, experiments.

Question 15

Describe an example of nomothetic approach to studying personality

Answer 15

Hans Eysenck’s type and Raymond Cattell’s 16PF trait theories are nomothetic approaches to studying personality.

They both assume that there are a small number of traits that account for the basic structure of all personalities and that individual differences can be measured along these dimensions.

In the past 20 years a growing consensus has begun to emerge about what those traits are. The “big 5” are considered to be extroversion, agreeableness, conscientiousness, emotional stability and openness to experience.

From a nomothetic point of view these are considered to adequately describe the psychologically significant aspects of any personality.

Question 16

Detail the idiographic approach

Answer 16

• Focus on individuals and the unique variables within an
individual.
• Study of individual people, one at a time.
• Differences between individuals viewed as greater than
similarities.
• Studied using non-experimental methods such as case studies, interviews, diaries.

Question 17

Describe an example of nomothetic approach to studying personality

Answer 17

Freud’s psychodynamic approach is nomothetic as he assumed he had created universal laws of personality development. However, Freud extensively used idiographic case studies detailing the lives of his patients.

The humanist approach adopts an idiographic approach as Carl Rogers believed that there are as many different personalities as there are people (personality unique to the individual), he studied it through case studies and developed the Q Sort procedure.

Question 18

Detail what it means by nomothetic and idiographic approaches should not be seen as conflicting

Answer 18

It is more helpful to see them as complementary. The insights from an idiographic approach can shed more light on the general principles developed using the nomothetic approach.

As always, it is best to take a combined approach. Millon & Davis (1996) suggest research should start with a nomothetic approach and once general ‘laws’ have been established, research can then move to a more idiographic approach. Thus, getting the best of both worlds!

Question 19

Detail any applications of individual differences

Answer 19

• Job - determine suitability for the job using psychometric tests, interviews, screening etc.
• School - tests to explore competency/ability. 11+ test. Aptitude tests in uni
• Healthcare - questionnaires determine severity and treatment (are they suitable or reliable tho?)

Question 20

What are the major and subdivisions of personality that can be reliably assessed?

Answer 20

Openness to new experience: Feelings, Ideas, Values, Actions, Fantasy, Aesthetics

Conscientiousness: Competence, Achievement striving, Self-discipline, Orderliness, Dutifulness, Deliberation

Extraversion: Gregariousness, Activity level, Assertiveness, Excitement seeking, Positive emotions, Warmth

Agreeableness: Trust, Altruism, Straightforwardness, Compliance, Modesty, Tender-mindedness

Neuroticism: Anxiety, Self-consciousness, Depression, Vulnerability, Impulsiveness, Angry hostility

Question 21

Detail the Big Five Personality test

Answer 21

Background
The big five personality traits are the best accepted and most commonly used model of personality in academic psychology. If you take a college course in personality psychology, this is what you will learn about. The big five come from the statistical study of responses to personality items. Using a technique called factor analysis researchers can look at the responses of people to hundreds of personality items and ask the question “what is the best was to summarize an individual?”. This has been done with many samples from all over the world and the general result is that, while there seem to be unlimited personality variables, five stand out from the pack in terms of explaining a lot of a persons answers to questions about their personality: extraversion, neuroticism, agreeableness, conscientiousness and openness to experience. The big-five are not associated with any particular test, a variety of measures have been developed to measure them. This test uses the Big-Five Factor Markers from the International Personality Item Pool, developed by Goldberg (1992).

Procedure
The test consists of fifty items that you must rate on how true they are about you on a five point scale where 1=Disagree, 3=Neutral and 5=Agree. It takes most people 3-8 minutes to complete.

Question 22

What are population norms?

Answer 22

A study might, for example, give a mean level of anxiety separately for men and women aged between 20 and 29, another for men and women aged between 30 and 39 and so on. These calculations give the population norms for that particular characteristic. Population norms represent the mean scores that particular groups of individuals score on a specific test. For example, they allow you to compare the test score on anxiety for a woman between ages 20 and 29 with the mean levels for her age group of women. You can then conclude that her anxiety score was either above or below the average for her age group as well as comparing her with other individuals in your sample. This information gives profiles of individual differences that are then frequently used to define types of personalities. Trait theorists frequently use population norms.

Question 23

Describe Carver and Scheier (2000) interpretation of the idiographic v nomothetic approach

Answer 23

Carver and Scheier (2000) argue that within personality theorising, the distinction between idiographic and nomothetic is not clear-cut. They argue that psychologists adopting the nomothetic approach still accept the uniqueness of individuals. However, they do not accept that there is an infinite number of personality variables. They see that there is an underlying common structure of personality with an associated finite number of personality variables. The uniqueness of the individual comes from their particular mix of variables from the finite set. It is how these personality variables are combined that makes each individual unique. Some idiographic researchers also go beyond the focus purely on the individual. They collect sets of case studies, for example, and then identify common themes across these case studies. In this way, they can generate theories and make predictions that can be tested, often by using nomothetic approaches.

Question 24

Detail distinctions and assertions in personality research

Answer 24

Personality is perceived to be a relatively stable, enduring, important aspect of the self. People may act differently in 9 different situations, but personality will have a major influence on their behaviour.

While it is accepted that individuals can and do change over time, there is a contention that personality is relatively stable over time. People may learn from their mistakes and change their behaviour; but the more profound the change, the longer it generally takes. Changing aspects of ourselves is typically not easy, as counsellors and therapists will attest. It tends to take considerable time and effort for individuals to change aspects of themselves, if indeed they are successful. Expert help is frequently needed from counsellors or therapists before change is achieved.

Psychologists, through their research over time, have identified the personality characteristics that can be reliably assessed, where differences make most impact on behaviour and are most consistent over time (the Big Five).

Personality theorists make a further distinction between the overt, observable aspects of personality and the unobservable aspects of personality such as thoughts, memories and dreams.

The psychoanalytic theoretical school goes further, making a distinction between the conscious and unconscious aspects of personality. Specific drives or mechanisms of which the individual is unaware are thought to be influential in determining personality. From specific examples of behaviour or habitual styles of behaving, the existence of these personality characteristics in the individual are inferred.

A further distinction is often made between what is called the individual’s private persona and his/her public persona. The private persona is conceptualised as being the ‘real’ inner person, while the public persona is the way that individuals present themselves to the outside world. Measures of personality and theoretical explanations are considered to define the persona.

Question 25

Detail the effects of personality versus situational effects

Answer 25

Some social psychologists, especially social deconstructionists, claim that it is the situation that largely dictates how we behave, whereas personality theorists argue that individual personality plays a crucial role in shaping our behaviour whatever the situation. Individuals do behave differently in different situations. We may be confident and outgoing in some situations and less sure of ourselves and more retiring in other situations, but it is not simply the situation that influences our behaviour. Even in what are described as highly socially proscribed situations – that is, situations where the behavioural choices open to individuals are limited as there are rules that have to be followed – individual differences in behaviour can be observed.

Most psychologists would accept that most behaviour results from an interaction between the effects of personality and the dictates of the situation.

Question 26

Detail some issues with measurement of personality

Answer 26

The methods of measuring important personality characteristics have to be reliable. This is obviously important if you are going to use personality tests to assess individuals for training or further education or as a tool to aid staff recruitment in an organisation. With the organisational example, you need to identify which factors are relevant to performance within the specific organisational context, whether these can be consistently and reliably measured, and whether they are relatively enduring over time. It is not a simple exercise, as the example on occupational testing in ‘Stop and think: Occupational testing’ demonstrates. We shall return to issues of assessment later, as it is a critical area for psychologists to get right.

Question 27

Describe occupational testing

Answer 27

Many organisations now use psychometric testing as part of employee selection. The underlying principles are simple. If we know the demands made by a job in terms of personality and abilities, then we can test individuals and match them against the job requirements. It is estimated that somewhere between 50 and 70 per cent of companies use some form of testing to select their employees. Testing should help to improve job selection, but there are dangers.

Question 28

Describe the Ancient Greek philosopher and teacher Aristotle (384–23 bce) contribution to the study of personality

Answer 28

He was the first person to write about individual differences in character and how these relate to behaviour. He suggested that personality characteristics, such as modesty, vanity and cowardice, determined how moral or immoral individuals were.

Question 29

Describe the Ancient Greek philosopher Plato (428/427–348/347 bce) theory of personality

Answer 29

Plato wrote that knowledge was not ‘given’ by the senses but acquired through them, and it was intelligence through reason that organised and made sense out of what was perceived. Both Plato and Aristotle believed that active intellect explained intellectual activities such as thinking and intuition.

Question 30

What does Plato’s allegory of the cave have to do with individual differences?

Answer 30

• Hints at the notion of latent variables
• Prisoners can only observe the shadows
• The origin of these shadows is unknown
• The prisoners interpret reality from their observations.
• Much of differential psychology is about identifying
underlying latent variables that can explain observed
behaviours.
• Psychometrics is an area of differential psychology that is concerned with the measurement of latent variables.

Question 31

Detail Plato’s Tripartite Theory of the Soul

Answer 31

In The Republic, Plato defines his idea that there is a tripartite soul. In other words, each person’s soul is divided into three different parts, and these parts are simply in different balance from one person to the next.

Plato defines the soul’s three parts as the logical part, the spirited part, and the appetitive part.

Question 32

Detail the appetitive part of Plato’s Tripartite Theory of the Soul

Answer 32

The appetites, which includes all our myriad desires for various pleasures, comforts, physical satisfactions, and bodily ease. There are so many of these appetites that Plato does not bother to enumerate them, but he does note that they can often be in conflict even with each other. This element of the soul is represented by the ugly black horse on the left.

Question 33

Detail the spirited part of Plato’s Tripartite Theory of the Soul

Answer 33

The spirited, or hot-blooded, part, i.e., the part that gets angry when it perceives (for example) an injustice being done. This is the part of us that loves to face and overcome great challenges, the part that can steel itself to adversity, and that loves victory, winning, challenge, and honour. (Note that Plato’s use of the term “spirited” here is not the same as “spiritual.” He means “spirited” in the same sense that we speak of a high-spirited horse, for example, one with lots of energy and power.) This element of the soul is represented by the noble white horse on the right.

Question 34

Detail the logical part of Plato’s Tripartite Theory of the Soul

Answer 34

The mind (nous), our conscious awareness, is represented by the charioteer who is guiding (or who at least should be guiding) the horses and chariot. This is the part of us that thinks, analyses, looks ahead, rationally weighs options, and tries to gauge what is best and truest overall.

Question 35

Name and order the three parts of Plato’s Tripartite Theory of the Soul

Answer 35

• The first part of the tripartite soul is the logical part (logistikon).
• The second part of the tripartite soul is the spirited part (thymoeides).
• The third part of the soul is the appetitive part (epithymetikon).

Question 36

Describe the difference between Plato and Freud’s theories

Answer 36

Both Plato and Sigmund Freud have accounts of human nature; they describe three agencies of action within the psyche, which can be taken to mean “mind” or “soul.” But they differ on what some of these agencies are, on the relative influence of some of the agencies, and on the moral precepts to be derived. Plato’s is the much older position, of course―not dependent upon, or taking account of, the somewhat controversial psychoanalytic techniques developed by Freud in the late nineteenth and early twentieth centuries.

Question 37

Detail Freud’s (1923) theory of the structure of personality

Answer 37

Freud proposed that our psyche (personality) has 3 components: the ego (represents our conscious thoughts), the superego (represents our social conscience and the id (represents subconscious, pleasure seeking and inner desires).

The ego develops strategies to defend yourself from daily conflicts that cause stress or anxiety due to the id’s desires and superego’s attempt to control these desires. These protective strategies are called defence mechanisms.

Question 38

Describe Theophrastus’ (student of Aristotle) contribution to study of personality

Answer 38

Theophrastus continued Aristotle’s work and observed and wrote short stories/paragraphs about 30 personality types through a lexical approach.

Question 39

What is taxonomy of classification?

Answer 39

Taxonomic classification is the act of placing an object or concept into a set or sets of categories (such as a taxonomy or a subject index), based on the properties of the object or concept. A person may classify the object or concept according to an ontology.

Question 40

What is a lexical approach?

Answer 40

The lexical approach is based on the assumption that the most important personality traits are encoded as words in natural languages and that the analysis of the structure of those words may lead to a scientifically acceptable personality model.

Question 41

What impact did the age of enlightenment have on differential psychology?

Answer 41

• Mid 17thC to 18th C - intense revolutions in science,
philosophy, society and politics.
• Key figures in the development of differential psychology.

Question 42

What impact did Rene Descartes (1596-1650) have on differential psychology?

Answer 42

René Descartes was a French mathematician and philosopher from the 1600s. He theorised that the body and mind are separate entities. The body was viewed as a physical entity and the mind as a spiritual entity. Descartes believed that the two interacted only through a tiny structure at the base of the brain called the pineal gland. His position of the mind and body as separate entities became known as dualism. According to dualism, the body’s behaviour is scientifically measurable, however the mind is not, as it transcends the material world.

Descartes developed a theory of mind as an immaterial, non-extended substance that engages in various activities or undergoes various states such as rational thought, imagining, feeling (sensation), and willing. Matter, or extended substance, conforms to the laws of physics in mechanistic fashion, with the important exception of the human body, which Descartes believed is causally affected by the human mind and which causally produces certain mental events. For example, willing the arm to be raised causes it to be raised, whereas being hit by a hammer on the finger causes the mind to feel pain. This part of Descartes’s dualistic theory, known as interactionism, raises one of the chief problems faced by Descartes and his followers: the question of how this causal interaction is possible.

Question 43

Describe Thomas Hobbes’ (1588-1679) impact on differential psychology

Answer 43

Thomas Hobbes and John Locke were English philosophers who disagreed with the concept of dualism. They argued that all human experiences are physical processes occurring within the brain and nervous system. Thus, their argument was that sensations, images, thoughts and feelings are all valid subjects of study. As this view holds that the mind and body are one and the same, it later became known as monism. Today, most psychologists reject a rigid dualist position since many years of research has indicated that the physical and mental aspects of human experience are intertwined.

Question 44

Describe John Locke’s’ (1588-1679) impact on differential psychology

Answer 44

• At birth the mind is a blank slate (tabula rasa).
• We are born without innate ideas, and knowledge is instead
determined only by experience derived from sense perception.
• Nature vs NURTURE.

Question 45

Describe Charles Darwin’s (1809-1882) impact on differential psychology

Answer 45

Galton strongly believed, following on from
Darwin’s theories of evolution and natural selection, that “we should attempt to exert control over
organic evolution in the same way as we exert
control over the physical world and to direct it into
channels of our own choosing”.4 This would provide practical applications for Darwin’s theories
and replace his idea of natural selection by a type
of artificial selection. The publication of Darwin’s
Origin of Species in 1859 and the elaboration of his
theory of evolution by natural selection provoked
both bitter theological controversies with the
creationist proponents of the animal world as well
as spirited debates on its application to social
progress and reform. The subject of eugenics was initiated by Francis Galton with considerable support from Charles Darwin in the latter half of the 19th century.

Question 46

Define eugenics

Answer 46

Eugenics can be defined as the use of science applied
to the qualitative and quantitative improvement of
the human genome.

Question 47

Give a brief history on eugenics

Answer 47

The past history of eugenics has been appalling,
with gross abuses in the USA between 1931 and
1945 when compulsory sterilisation was practised;
and in Germany between 1933 and 1945 when mass
extermination and compulsory sterilisation were
performed. To prevent such abuses in the future
statutory bodies, such as a genetics commission,
should be established to provide guidance and rules of
conduct for use of the new information and
technologies as applied to the human genome.
(Journal of Medical Ethics 1998;24:99-105)

Question 48

How did eugenicists determine ‘gifted individuals’

Answer 48

1) Name, place and date of birth, address, occupation. Parent occupations.
2) Have you undergone a physical fitness examination? State particulars and date.
3) Can you refer to any physical competition in which you ranked higher than average?
4) Have you performed any physical feats that were beyond the powers of men of the
same age and training to yourself?
5) Have you been awarded prizes or other distinctions at any large college, school or
university, or by any literary or scientific body?
6) Have you been elected to any coveted post of trust, paid or unpaid, in any school or
college, or in any association, whether it be athletics, scholastic or other?

Question 49

What is psychometrics?

Answer 49

Psychometrics is the field of study concerned with the theory and technique of psychological measurement, which includes the measurement of knowledge, abilities, attitudes, and personality traits through the construction and validation of questionnaires. The field is primarily concerned with the study of differences between individuals.

Question 50

Detail Adolphe Quetelet’s (1796 – 1874) social physics

Answer 50

• He was the first person to systematic application of statistical methods to
humans– ‘Social mechanics’ or ‘social physics’
• The ‘Average Man’
• Body Mass Index – aka the Quetelet index
- “weight increases as a square of the
height”
• Comparison to the norm
• Primary interest in defining the characteristics of the normal man
- ‘Normal distribution’
• Extended beyond the physical characteristics to include
behaviours, mind and soul.
• Founder of the social sciences and statistical testing

Question 51

Detail Francis Galton’s departure from the average

Answer 51

• Influenced by Quetelet
• Interests centred on differences and deviation from the norm (e.g. extremely intelligent people to select for breeding)
• Developed standard deviation - mechanism to identify ‘gifted’ individuals
• Eugenics

Question 52

What are latent variables?

Answer 52

In statistics, latent variables are variables that are not directly observed but are rather inferred from other variables that are observed. Mathematical models that aim to explain observed variables in terms of latent variables are called latent variable models.

Question 53

Explain why measuring psychological individual differences is different to biological or physical differences

Answer 53

Indirect rather than direct and thus requires the development of valid and reliable tools. We need to develop ways of measuring these underlying
variables – also known as ‘latent variables’.
• Multiple items
• Reliability and validity (comparison with objective
measures)
• Social desirability biases

Question 54

What is factor analysis?

Answer 54

Factor analysis is a technique that is used to reduce a large number of variables into fewer numbers of factors. This technique extracts maximum common variance from all variables and puts them into a common score. As an index of all variables, we can use this score for further analysis.

• Theory development - emerging patterns inform theory development
• Questionnaire creation and refinement - e.g. start with 60 reduce to 20

Question 55

How did Charles Spearman measure intelligence?

Answer 55

o Use of factor analysis in development of his two factor theory of intelligence ‘G’.
• Tests of different skills on 24 school children from a small village e.g., Memory, Spatial abilities, Mathematical abilities, Vocabulary.
He measured 3 intellectual measures: School Cleverness, Common Sense A and Common Sense B. His results showed the average r between intellectual and sensory measures to be +.38, School Cleverness and Common sense to be at +0.55, and the three tasks intercorrelated at +0.25. This data was looked at other populations including high school. Spearman proposed that intellectual and sensory measure be combined as assessment of general intelligence
• Observed a positive correlation between
scores on different tests, e.g. if a child did well on a maths test likely to do well on the other tests. Known as the “positive manifold”.

Spearman believed that general intelligence represented an intelligence factor underlying specific mental abilities. All tasks on intelligence tests, whether they related to verbal or mathematical abilities, were influenced by this underlying g-factor.

Many modern intelligence tests, including the Stanford-Binet, measure some of the cognitive factors that are thought to make up general intelligence, e.g. knowledge, working memory and quantitative reasoning.

Spearman proposed that his two-factor theory has two components. The general intelligence, g, another component influences abilities on a particular task. To explain the differences in performance on different tasks, Spearman hypothesised that this other component was specific to a certain aspect of intelligence. This second factor he named s, for specific ability. Regarding g, Spearman saw individuals as having more or less general intelligence, while s varied from person to person on a task. In 1999, behaviour geneticist Robert Plomin described g by saying: “g is one of the most reliable and valid measures in the behavioural domain… and it predicts important social outcomes such as educational and occupational levels far better than any other trait.