psychological investigations experiments

PSYCHOLOGICAL INVESTIGATIONS EXPERIMENTS

AS Psychology

QUESTION: WHAT MAKES A

PIECE OF RESEARCH AN EXPERIMENT?

AS Psychology

VariablesA basic experiment has two variables.

A variable is ...

In psychological experiments we use two types of variables:

Independent Variable – is the variable the experimenter manipulates

Dependent Variable – is the variable the experimenter measures

A thing which can vary or change. 

ACTIVITY!

Each person will read out their experiment description

If you have the card with the correct IV, stand up and read it

Then it’s the turn of the person with the correct DV

Do students recall more words from a list in the morning or evening?

IV? DV?

IV: TIME OF DAY TESTED DV: NUMBER

OF WORDS RECALLED

Can students identify actors’ faces better straight after a film or after a delay of 30 mins?

IV? DV?

IV: TESTED IMMEDIATELY OR AFTER 30

MINSDV: NUMBER

OF FACES IDENTIFIED

Does listening to music while revising affect A level grades?

IV? DV?

IV: MUSIC OR NO MUSIC DV: A LEVEL

GRADES

Are reaction times slower for drivers who have had 4 hours sleep or 8 hours sleep?

IV? DV?

IV: 4 OR 8 HOURS SLEEP

DV: TIME TAKEN TO

REACT TO A STIMULUS

Will football fans be able to remember a list of football scores better than non-football fans?

IV? DV?

IV: FOOTBALL FAN OR NOT

DV: NUMBER OF SCORES RECALLED

FROM A LIST

Do women read facial expressions better than men?

IV? DV?

IV: PARTICIPANT

GENDERDV: FACIAL

EXPRESSIONS CORRECTLY IDENTIFIED

Will participants complete more press-ups when in competition with other people than alone?

IV? DV?

IV: COMPETING

WITH OTHERS OR ALONE

DV: NO. OF PRESS-UPS COMPLETED

Does caffeine affect ability to understand new mathematical concepts?

IV? DV?

IV: TEA/COFFEE/COKE DRUNK OR

NO DRINK

DV: GRADE IN A MATHS TEST AFTER A NEW

TOPIC

What is a hypothesis??????

A hypothesis is a statement or prediction

of the results you expect to find after your experiment.

It must include descriptions of the IV and DV

Examples from studies you know: Maguire:There will be a difference between the

hippocampi of taxi-drivers and non-taxi-drivers

GriffithsThere will be no differences in the skill levels of

RGs and NRGs

Dement & KleitmanThere will be an association between

REM sleep and dreaming

What does ‘operationalisation’ mean?

Ensuring that variables are in a form that is easily

testable / measurable; it has to be very specific so

that the reader knows exactly what you mean and

how you are going to measure that variable

Try operationalising these DVs:Educational attainmentMemoryDriving skillHappinessHelpfulness

Null HypothesesAs well as writing an ‘experimental’ hypothesis when carrying out research, you will also need to write a null hypothesis. What is a null hypothesis?

A null hypothesis is a statement that the IV will make no difference to the DV

Your hypotheses might be: Null hypothesis

There will be no difference in the exam performance of students whether they have a computer in their home or not

Alternative hypothesis:

Students who have a computer at home will achieve higher grades in their AS exams than those who don’t.

Your hypotheses might be: Null hypothesis Alternative

hypothesis:

People eating 5 portions of fruit and vegetables a day will live longer than those who don’t.

Your hypotheses might be: Null hypothesis

There will be no difference in the lifespans of those who eat 5 portions of fruit and veg a day and those who don’t.

Alternative hypothesis:

People eating 5 portions of fruit and vegetables a day will live longer than those who don’t.

Your hypotheses might be: Null hypothesis Alternative

hypothesis:

Men whose wives stay at home while they go out to work will have a happier marriage than those whose wives work

Your hypotheses might be: Null hypothesis

There will be no difference in the happiness of marriages whether the wife stays at home or goes out to work

Alternative hypothesis:

Men whose wives stay at home while they go out to work will have a happier marriage than those whose wives work

One-tailed and two-tailed hypothesesNOTE!: (these both refer to the alternative hypothesis, not the null)

One-tailed and two-tailed hypotheses

One-tailed hypotheses are predictions that state the

direction the results will go in. This is also known as a

‘directional hypothesis’.It states that not only will be there be an

effect but you know what effect that will be

Eg: Students will remember words better in a cold room than a warm one

One-tailed and two-tailed hypotheses

Two-tailed hypotheses are predictions that do not

state the direction the results will go in. This is also

known as a non-directional hypothesis.It states that you think there will be an

effect but you don’t know exactly what that effect will be

Eg: There will be a difference in the number of words students remember in a hot or cold room

One-tailed or two??

Think – does this state what the effect will be, or just that there will be an effect?

Boys score differently on aggressiveness tests from girls

One-tailed or two??

Think – does this state what the effect will be, or just that there will be an effect?

People remember the words that appear early in a list better than the words that appear later

One-tailed or two??

Think – does this state what the effect will be, or just that there will be an effect?

People given a list of emotionally charged words recall less than participants given a list of emotionally neutral words

One-tailed or two??

Think – does this state what the effect will be, or just that there will be an effect?

Hamsters are better pets than budgies

One-tailed or two??

Think – does this state what the effect will be, or just that there will be an effect?

Words presented in a written form are recalled differently from those presented in a pictorial form

Pick one of the following scenarios and write a null and an alternative hypothesis for it; then state whether you have written a one-tailed or two-tailed alternative hypothesisDo students recall more words from a list in the morning or evening?Can students identify actors’ faces better straight after a film or after a delay of 30 mins?Does listening to music while revising affect A-level grades?Are reaction times slower for drivers who have had 4 hours sleep or 8 hours sleep?Will football fans be able to remember a list of football scores better than non-football fans?Do women read facial expressions better than men?Do better-qualified people borrow more library books than people with few qualifications?

Experimental DesignIndependen

t Groups• Different

participants take part in each ‘condition’ of the study, e.g. one group studies with TV, one group without

Repeated Measures

• The same participants take part in two different conditions, e.g. studying for one test with TV, one without TV

Matched Pairs

• Participants are matched (e.g. two students with similar scores on earlier tests) and one takes part in each condition

EXPERIMENT 1- real words v. nonsense

You are going to take part in two experiments to demonstrate how each of these designs work in practice.

Repeated measures design Learn the items on the paper in front of you. You

have 1 min to study the items, after this time turn the sheet over and write down as many of the

items as you can remember.You have 1 minute to do this.

Repeated measures design

You will be given one more word list. 1 minute to memorise and then 1

minute to write down as many words as you can remember

(Nonsense and real words)

The same participants did both conditions

Click icon to add pictureThat was a repeated measures design experiment because.....?

Independent measures design; words v pictures

Each participant only takes part in one condition, e.g. Words or pictures.

Half the participants are allocated to one condition and half to the otherLet’s have a go at that now!

EXPERIMENT 2 - words v. pictures

Independent measures design You will ALL be a given a piece of paper for

which you must memorise the ten items for 1 minute and then you will be asked to write down as many items as you can remember in

1 minute.

(Words and pictures)

Different participants did both conditions

Click icon to add pictureThat was an independent measures design experiment because.....?

Experimental design.....

Strengths? Weakness

es?Ensure that you can think of strengths and weaknesses for repeated measures and independent measures designs. How might you overcome them? What about matched pairs?

See textbook p15

Strengths WeaknessesEnable you to test hypotheses by manipulating of an IV; therefore can assume cause and effect

Often low in ecological validity as the situations don’t reflect everyday life

Scientific as follow standardised procedures, enabling replication

Practical problems mean sample sizes are often small, reducing generalisability

Control extraneous variables, improving reliability

May stress participants due to unfamiliar tasks/surroundings

Often produce quantitative data which can be analysed

Often don’t get deep understanding due to lack of qualitative data

Strengths and weaknesses of experiments in general, compared with

other research methods

Strengths WeaknessesLab experiments High levels of control

means only the IV can affect the DV

Low in ecological validity meaning doesn’t tell us about real life behaviour

Field experiments Lower levels of control

Higher in ecological validity

Quasi experiments Only way of studying some IVs such as gender

Other features of the group may be confounding variable

Independent measures

No order effectsNo demand characteristics as they don’t guess the purpose of the study

Other features of the group may be confounding variable

Repeated measures

Removes individual differences as you are comparing the group against themselves

Order effectsGreater likelihood of demand characteristics

Matched participants

Extraneous variables are well controlled

Other variables may still exist

How might you have to use this

information on the exam paper?

Let’s have a

look......

Section B A researcher wants

to conduct an experiment to investigate if there is a difference in the memory ability of primary school pupils in the morning compared to the afternoon. Each pupil will be assessed in both the morning and the afternoon.

a) Describe and evaluate one way in which memory could be measured in this investigation (10)

b) Explain the difference between an independent and repeated measures design (4)

c) Outline one strength and one weakness of using a repeated measures design for this investigation (6)