Individual differences in human functioning
Individual differences are the special ways in which people differ from each other. We differ in height and colour, and also in thinking, feeling and behaving.
- Variability is found in all living things. No two leaves, and no two people, are exactly alike.
- Trait: a steady quality inside a person, like being shy or friendly.
- Situationism: the view that the situation strongly shapes behaviour. A person may be quiet in a temple and loud at a cricket match.
Behaviour = person (traits) + situation working together. Psychologists study both.
Why study differences?
It helps in schools (right help for each child), jobs (right person for the right work), and counselling (knowing oneself).
Psychological attributes we study
An attribute is a quality that can be measured. Five are most studied:
- Intelligence: the ability to understand, think well and adjust to the world.
- Aptitude: the hidden ability to learn a skill with training.
- Interest: what a person likes to do.
- Personality: a person's steady pattern of thinking, feeling and acting.
- Values: beliefs about what is good or important.
Attributes cannot be seen directly. We see behaviour and infer (guess carefully) the attribute.
Assessment of psychological attributes
Assessment means measuring a person's attribute using standard methods. Formal assessment is planned, fair and the same for all. Informal assessment changes from person to person and is less exact.
Methods of assessment
- Psychological test: a standard, objective measure of an attribute. A good test is reliable (gives the same result again), valid (measures what it says) and standardised (same rules and norms for all).
- Interview: talking face to face to gather information.
- Case study: a deep study of one person using many sources.
- Observation: watching behaviour in a planned way.
- Self-report: the person answers questions about themselves.
The bell curve
When many people take a test, most scores fall near the middle and few are very high or very low. This shape is called the normal curve.
Try it at home
Ask 10 family members or friends to hold their breath as long as they can. Write the seconds. Draw a bar for each range (0-20, 21-40, 41-60 s). You will see most people in the middle ranges. That is a small bell curve of individual differences.
Key formulas and definitions
- Individual differences: special ways in which people differ
- Behaviour = Person (traits) + Situation
- Five attributes: intelligence, aptitude, interest, personality, values
- Assessment: measuring attributes using standard methods
- Good test: reliable + valid + standardised
- Methods: test, interview, case study, observation, self-report
Worked examples
1. Riya is chatty at home but silent during a job interview. What does this show?
It shows situationism: the situation changes behaviour. Her trait (talkative) is present, but the formal interview situation holds it back. Behaviour depends on both person and situation.
2. A counsellor wants to know if Arjun will do well in engineering after training. Which attribute should be assessed?
Aptitude. Aptitude is the hidden ability to learn a skill with training, so it predicts future success in a field.
3. A psychologist studies one child with memory loss for many months using talks with parents, school records and tests. Which method?
A case study. It is a deep study of one person using many sources of information.
4. A test gives Neha 60 marks today and 30 marks next week, with no change in her. What is wrong with the test?
The test is not reliable. A reliable test gives nearly the same score each time for the same person.
Common mistakes
- Thinking individual differences mean only body differences. They include thinking, feeling and behaving too.
- Mixing up aptitude and intelligence. Intelligence is general ability; aptitude is the ability to learn a special skill.
- Believing only traits decide behaviour. The situation also matters (situationism).
- Calling any quiz a psychological test. A real test is standardised, reliable and valid.