• Created by: vicky
  • Created on: 26-04-11 11:39

Griffiths experiment.


In this study Mark Griffiths is investigating some of the cognitive differences between regular and non-regular gamblers. In particular he is interested in discovering whether regular fruit machine payers think differently to non-regular players. That is, whether regular fruit machine players display cognitive distortions.

Wagenaar argues that gamblers use a range of cognitive distortions called heuristics.


The aim of this study was to investigate cognitive bias involved in gambling behaviour.

There were three main hypotheses

There would be no difference between regular and non regular fruit machine gamblers on objective measures of skill.

Regular gamblers would produce more irrational verbalisations than non-regular gamblers

Regular gamblers would be more skill orientated than non-regular gamblers on subjective measures of self-report

A further hypothesis was also added that thinking aloud participants would take longer to complete the task than non-thinking aloud participants.


This study is using a quasi experimental approach. The main independent variable is whether participants are regular or non-regular gamblers.

The dependent variables are objective measurements of skill on the fruit machine, the content analysis of utterances from the thinking aloud method and the subjective measures of skill perception from the post-experimental semi-structured interview.

A further independent variable was created by a half of both the regular and non-regular gamblers being randomly assigned to the ‘thinking aloud’ condition.

The sample consisted of 60 participants. Most of the participants were recruited via a small poster advertisement circulated around a university and college campus. A number of the regular players were recruited via a regular gambler known to Griffiths.

The regular gamblers consisted of 29 males and 1 female and the mean age was 21.6 years.

The non regular gamblers consisted of 15 males and 15 females and the mean age was 25.5 years.

Each participant was tested individually at an arcade in the UK. All of the participants were asked to gamble on a fruit machine called ‘Fruitskill’ which played at 10 pence a go.

Each participant was given £3 to gamble on the fruit machine which gave them 30 ‘free’ gambles.

All of the participants were asked to try and stay on the machine for a minimum of 60 plays – which means that had to break even and win back £3 from the money they had put in.

If they managed to achieve 60 gambles with the initial £3 stake they were given the choice of either keeping any of the winnings or carry on gambling.

To measure the participants objective skill levels, Griffiths recorded the gamblers behaviour.

The experimenter stood nearby recording…


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