Tversky and Kahneman (1974)

• Highschool students were used as participants in this study
• Conditions of the study

  1. Ascending condition: estimate 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 in five seconds

  2. Descending condition: estimate 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1 in five seconds
• Anchoring bias


  The first number biases the participant’s estimate
• Results showed that ‘ascending condition’ participants had a median of 512
• Results showed that ‘descending condition’ participants had a median of 2250
• The real value is 40320
• Strengths of the study

  • Simple experiment
  • Establish reliability of findings
  • Highly controlled - high internal validity
• Limitations of the study

  • Low ecological validity - artificial situation
  • Independent measures design
• First number of the mathematical expression
biases the participants to estimate a lower number if the expression started with 1, and a higher number if the expression started with 9.