Key Study: Gandhi and the Anchoring Effect
Strack & Mussweiler, 1997

Travis DixonCognitive Psychology, Key Studies, Studies and Theories

This study tests the anchoring effect using guesses of Mahatma Ghandi (1869-1948).(Wikicommons).

Are we always in control of our thoughts, or can they be influenced by invisible forces? The art of persuasion and subtle manipulation is a fascinating field of study in psychology. In this post, we’ll look at how people can manipulate our cognitive biases to influence our decision-making. One of the more interesting cognitive biases  is the “anchoring effect.” 

The anchoring effect is “…a systematic influence of initially presented numerical values on subsequent judgments of uncertain quantities,” (Teovanovic, 2019). What does that mean? It means you can give someone a random number and that can influence their guess about the value of an unrelated item.

Can a pingpong ball affect how much we pay for champagne?

Let’s look at an example. Imagine you pick a pingpong ball out of a bag. That ball has a number written on it, let’s say, 99. You’re then given a bottle of champagne and asked to say for how much you are willing to buy that champagne. The chances are that you will say you are willing to spend more money than someone else who picked out a pingpong ball with the number 10 on it. Don’t believe me? You can see this demonstrated in this BBC documentary (watch from 23:10 link).

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In one of their earliest studies on the anchoring effect Daniel Kahneman and Amos Tversky got participants to spin a wheel. It was designed to land on 10 or 65. This was the “anchor.” They then asked the participants to guess what % of the countries in the United Nations were from Africa. If participants landed on 10 their average guess was 25%. If they landed on 65 their average guess was almost double at 45% (Kahmenan and Tversky, 1974 link).

According to the IB Psychology guide, the anchoring effect is an example of a heuristic and can be used in exams on questions about cognitive biases.

The anchoring effect is one of many cognitive biases that Kahneman and Tversky uncovered in their decades of research. It is also one of the most robust findings in cognitive psychology but it’s very difficult to explain. Before we get into trying to explain the anchoring effect, let’s look at one more interesting study.

Gandhi and the Anchoring Effect (Strack and Mussweiler, 1997)

This study shows that numbers that are impossibly linked to the target question can still have an effect. Their aim was to see how the anchoring effect could influence guesses of Mahatma Gandhi age when he died.

This study tests the anchoring effect using guesses of Mahatma Gandhi (1869-1948).(Wikicommons).


  • Participants were 60 male and female German University students.
  • They were asked two questions.
  • Half of the participants were asked if Gandhi was older or younger than 9 years old when he died.
  • The other half were asked if he was older or younger than 140 years old.
  • They were then asked how old they think he was when he died.


Participants in the high anchor condition guessed on average he was 67 years old, whereas those in the low anchor condition guessed he was 50 years old when he died.

Conclusions and Applications:

This study demonstrates the anchoring effect – numerical information given to participants before making a judgment can influence their later judgements. It also shows it can have an effect even if the numbers are implausible.


Anchoring and Availability Heuristic: One explanation is that the anchoring effect occurs because people begin their judgement with the anchor and then adjust step-by-step until they reach the desired answer. In the above example, participants in the high anchor condition might begin at 140 and realize this is far too high so adjust by reducing the number until they get to something that seems reasonable. The same would work for the low anchor condition, but they adjust upwards.

The anchor is the information that is easily accessible (available) and this is used in the judgement. (A heuristic is a cognitive short-cut, so here the anchor is used as a short-cut to making a guess).

Dual Processing Model: A second explanation is that System 1 and System thinking can explain anchoring. In terms of System 1 (fast, intuitive, automatic), participants’ anchor-consistent knowledge is activated by the anchor. This influences their guess. For example, people in the 140 condition might link this number to the fact that Gandhi was old when he died, so 67 sounds about right.On the other hand, those in the 9 condition might have some other knowledge activated, like he died too young (he was assassinated), resulting in a lower guess.

Alternatively, they might use System 2 processing if they start their guess with the anchor and then re-adjust from there. e.g. they know 140 is too high so they make readjustments. This requires more cognitive effort than the first approach. (Teovanovic, 2019).

IB Psychology IA Anchoring effect studies can be used for the internal assessment. Before they’re used, make sure students can provide one theoretical explanation for the effect. This will help them get top marks.

Critical Thinking Considerations

  • Do you think all people are equally vulnerable to the anchoring effect? There are numerous studies that show some types of people are more vulnerable than others. Can you hypothesize what character traits might be related to anchoring?
  • The anchoring effect has been applied in marketing. How do you think it could be used?


  • Teovanović, Predrag. Individual Differences in Anchoring Effect: Evidence for the Role of Insufficient Adjustment. Europe’s Journal of Psychology | 1841-0413 (Link)
  • Fritz Strack and Mussweile, Thomas. Considering the Impossible: Explaining the Effects of Implausible Anchors. Social Cognition, Vol. 19, No. 2, 2001, pp. 145-160 (Link)(Link 2)
  • Fritz Strack and Mussweile, Thomas. Explaining the Enigmatic Anchoring Effect: Mechanisms of Selective Accessibility. Journal of Personality and Social Psychology, 1997, Vol. 73, No. 3, 437-446. (Link)