The Dual Processing Model argues that there are two ways in which we make decisions.  First, there is System 1 thinking; this system is the one that is reliant on past information and schema with the goal of making a quick and effortless decision based on limited information.  System 2 thinking, however, is much more effortful and requires more conscious reasoning.

When we use System 1 thinking we tend to use mental short-cuts called heuristics.  One example of a heuristic is “anchoring bias.”  Anchoring bias occurs when we rely too heavily on an initial piece of information offered (considered to be the "anchor") when making decisions. Often this information is numeric.

In the courtroom, in many countries, often a sentence is demanded or recommended by a prosecutor.  Psychologists Englich and Mussweiler wanted to know if the simple request for a certain length of prison sentence would unduly influence the decision made by a judge.

To test their hypothesis that the recommended sentence proposed by a prosecutor would unduly influence a judge’s decision, the researchers used an independent samples design.  This allowed the researchers to use the same case study for both conditions – the high anchor and the low anchor.

In order to control for the level of courtroom experience, the sample was made up of 19 young trial judges (15 male and 4 female) – with an average age of 29.37 and with an average of 9.34 months of experience.

The participants were given a case of alleged rape.  The prosecutor in one condition demanded a sentence of 2 months vs. 34 months.

To develop the case materials, advice was sought from highly experienced trial judges.  Then the case materials were tested on a group of 24 senior law students – this served as a pilot study.  The average recommended prison term suggested by the law students was 17.21 months.   This was then used as a basis for determining the anchors.

Participants were given the case materials along with copies of the penal code. They were asked to read through the materials and form an opinion about the case.  After they had formed an opinion about the case (about 15 minutes), they were given a questionnaire.  Half of the participants were told that the prosecutor demanded a 34-month sentence; while the other half were told that he demanded a 2-month sentence.

They were then asked the following questions:

• Do you think that the sentence was too low, adequate or too high?
• What sentence would you recommend?
• How certain are you about your sentencing decision? (a scale of 1 – 9)
• How realistic do you think this case is? (a scale of 1 – 9)

The average rating for the realistic nature of the case was 7.17, with a standard deviation of 1.3.  The judges' certainty about their responses, however, were not as strong, with an average rating of 4.53 and a standard deviation of 2.29.

When presented with a low anchor of two months, the average sentence was 18.78 months, with a standard deviation of 9.11.  in the high anchor condition of 34 months, the average sentence was 28.70 months, with a standard deviation of 6.53.

The study was a true experiment, allowing the researchers to infer a cause and effect relationship between the value of the anchor and the sentence.

The use of an independent samples design means that participant variability may have played a role in the results - serving as a confounding variable.

The sample size is small.  It is difficult to generalize the findings. In addition, the sample was limited in courtroom experience - which means that the results can best be generalized to younger, less experienced judges.

The use of the pilot group helped to establish reasonable anchors.  In addition, the pilot group demonstrated System 2 thinking, serving as a control group for the other two conditions, which demonstrated System 1 thinking.

The low scores on the judges' sense of confidence indicate that they may have been aware that their judgment was being influenced by other factors.