18.1.9
Griffiths on Cognitive Bias
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Griffiths (1994): Cognitive Biases Using Fruit Machines
Griffiths recorded the verbalisations of 30 gamblers and 30 non-gamblers as they played on fruit machines. He concluded that gamblers were more likely to have cognitive biases, specifically the illusion of control.

Method
- The field study compared 30 gamblers to 30 people who played fruit machines occasionally.
- Each of the players was given £3, the equivalent of 30 gambles on a fruit machine.
- The players were told to think aloud during their play and to get to 60 gambles.

Method cont.
- If they reached 60, they had a choice to keep playing or take any winnings they had received.
- Griffiths recorded:
- The number of gambles.
- The players’ verbalisations of their thoughts.
- The number of wins.
- The outcome of each specific gamble.

Results
- Initially, some of the regular gamblers refused to play on the specific fruit machine the researchers assigned them.
- Regular gamblers were more likely than the occasional players to play to 60 gambles.
- The regular gamblers also were more likely to play until they had lost all of their money.

Results cont.
- The regular gamblers had more irrational verbalisations, such as talking to the machine.
- E.g. This machine doesn't like me.
- They also referred to lost gambles as ‘near misses’ or ‘near wins’.
- Finally, in a post-gamble interview, the gamblers believed themselves to be more skilful than the occasional players.
Griffiths (1994): Cognitive Biases Using Fruit Machines
Griffiths recorded the verbalisations of 30 gamblers and 30 non-gamblers as they played on fruit machines. He concluded that gamblers were more likely to have cognitive biases, specifically illusion of control.

Conclusions
- Gamblers are more likely to demonstrate cognitive distortions. - Specifically, they are likely to show illusion of control, where they believe themselves to be more skilful than the occasional gamblers.
- Note that the fruit machines are a game of chance where there is no skill involved.

Conclusions cont.
- Additionally, they believed if they were familiar with the specific machine, they were more likely to win. This is why some refused to play on their designated machine at first.
- Finally, they also showed distorted views of reality by personifying and talking to the machines.

Evaluation
- This was a field study, which means it was done on location in a casino. So this shows high ecological validity.
- But in field studies, it is difficult to control for extraneous variables.
- An example of an extraneous variable could have been the effect of other people/gamblers nearby.

Generalisability
- The sample was also not representative of the whole population because only one female gambler participated, so the results should not be generalised to the entire population.

Validity
- Lastly, the study was trying to record cognitive distortions, which take place internally.
- But the participants were asked to verbalise them, which may have altered their thinking.
- So the study’s results may be invalid.
1Social Influence
1.1Social Influence
2Memory
2.1Memory
3Attachment
3.1Attachment
4(2026 Exams) Psychopathology
4.1Psychopathology
5(2027 Exams) Clinical Psychology & Mental Health
5.1Clinical Psychology & Mental Health
6Approaches in Psychology
6.1Approaches in Psychology
6.2Comparison of Approaches (A2 only)
7Biopsychology
7.1Biopsychology
8Research Methods
8.1Research Methods
8.2Scientific Processes
8.3Data Handling & Analysis
9Issues & Debates in Psychology (A2 only)
9.1Issues & Debates in Psychology (A2 only)
10Option 1: Relationships (A2 only)
10.1Relationships: Sexual Relationships (A2 only)
10.2Relationships: Romantic Relationships (A2 only)
10.3(2026 Exams) Relationships: Virtual (A2 only)
10.4(2027 Exams) Relationships: Online (A2 only)
11Option 1: Gender (A2 only)
11.1(2026 Exams) Gender (A2 only)
11.2(2027 Exams) Gender (A2 only)
12Option 1: Cognition & Development (A2 only)
12.1Cognition & Development (A2 only)
13Option 2: Schizophrenia (A2 only)
13.1Schizophrenia: Diagnosis (A2 only)
13.2Schizophrenia: Treatment (A2 only)
14Option 2: Eating Behaviour (A2 only)
14.1Eating Behaviour (A2 only)
15Option 2: Stress (A2 only)
15.1Stress (A2 only)
16Option 3: Aggression (A2 only)
16.1Aggression: Physiological (A2 only)
16.2Aggression: Social Psychological (A2 only)
17Option 3: Forensic Psychology (A2 only)
17.1Forensic Psychology (A2 only)
18Option 3: Addiction (A2 only)
18.1Addiction (A2 only)
18.2Treating Addiction (A2 only)
Jump to other topics
1Social Influence
1.1Social Influence
2Memory
2.1Memory
3Attachment
3.1Attachment
4(2026 Exams) Psychopathology
4.1Psychopathology
5(2027 Exams) Clinical Psychology & Mental Health
5.1Clinical Psychology & Mental Health
6Approaches in Psychology
6.1Approaches in Psychology
6.2Comparison of Approaches (A2 only)
7Biopsychology
7.1Biopsychology
8Research Methods
8.1Research Methods
8.2Scientific Processes
8.3Data Handling & Analysis
9Issues & Debates in Psychology (A2 only)
9.1Issues & Debates in Psychology (A2 only)
10Option 1: Relationships (A2 only)
10.1Relationships: Sexual Relationships (A2 only)
10.2Relationships: Romantic Relationships (A2 only)
10.3(2026 Exams) Relationships: Virtual (A2 only)
10.4(2027 Exams) Relationships: Online (A2 only)
11Option 1: Gender (A2 only)
11.1(2026 Exams) Gender (A2 only)
11.2(2027 Exams) Gender (A2 only)
12Option 1: Cognition & Development (A2 only)
12.1Cognition & Development (A2 only)
13Option 2: Schizophrenia (A2 only)
13.1Schizophrenia: Diagnosis (A2 only)
13.2Schizophrenia: Treatment (A2 only)
14Option 2: Eating Behaviour (A2 only)
14.1Eating Behaviour (A2 only)
15Option 2: Stress (A2 only)
15.1Stress (A2 only)
16Option 3: Aggression (A2 only)
16.1Aggression: Physiological (A2 only)
16.2Aggression: Social Psychological (A2 only)
17Option 3: Forensic Psychology (A2 only)
17.1Forensic Psychology (A2 only)
18Option 3: Addiction (A2 only)
18.1Addiction (A2 only)
18.2Treating Addiction (A2 only)
Practice questions on Griffiths on Cognitive Bias
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