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Simple Jury Persuasion: When you want to stack the jury with extraverts

Friday, July 29, 2011
posted by Douglas Keene

Extraverts are the ones in the jury box who are making plans for lunch and organizing jury reunion parties.  They chat up their bench-mates during voir dire, and can be seen making good-natured eye contact with everyone in the courtroom. They are also, according to some new research, more likely to believe in free will, and that may be a good thing (or perhaps a bad thing) for your case.

Researchers in Germany wanted to study whether personality characteristics (in this case, extraversion) would be related to a belief in free will (and therefore, ultimate responsibility for one’s actions).

Participants in a study in Berlin, Germany read the following scenario (of course it was presented in German, but we figured most of our readers would rather see it in English):

Most respected neuroscientists are convinced that eventually we will figure out exactly how all of our decisions and actions are entirely caused. For instance, they think that whenever we are trying to decide what to do, the decision we end up making is completely caused by the specific chemical reactions and neural processes occurring in our brains. The neuroscientists are also convinced that these chemical reactions and neural processes are completely caused by our current situation and the earlier events in our lives, and that these earlier events were also completely caused by even earlier events, eventually going all the way back to events that occurred before we were born.

So, if these neuroscientists are right, then once specific earlier events have occurred in a person’s life, these events will definitely cause specific later events to occur. For instance, once specific chemical reactions and neural processes occur in the person’s brain, they will definitely cause the person to make the specific decision he or she makes. So, once specific earlier events have occurred in a person’s life, these events will definitely cause specific later events to occur.

For example, one day a person named John decides to kill a shop owner, because he needs money and does it. Once the specific thoughts, desires, and plans occur in John’s mind, they will definitely cause his decision to kill a shop owner. (Nahmias et al., 2007).

Participants were asked to rate their level of agreement with the following statements on a scale from 1 (absolutely disagree) to 7 (absolutely agree):

1. John is morally responsible for his action.

2. John did it because of his own free will.

3. John’s decision was up to him.

Researchers found that the extraverts were more likely to focus on moral responsibility and free will in their evaluations of “John’s” behavior. They were less likely to listen to mitigating explanations [such as brain-based rationales] for John’s behavior. Data analysis showed that individual “warmth” explained much of this tendency in extraverts. It is possible that extraverts experience increased empathy for whoever is harmed in the interaction. Obviously, this would play better for one side of a dispute than the other.

The researchers also questioned (given the strong relationship of personality style to the support of free will/responsibility) whether we can really trust the objectivity of expert witnesses as they examine case data. Depending on the personality style, the expert witness may support one explanation or the other [unless accepting payment to support a particular position].

There is an old saying that floats around saying introverts are about 25% of the population and extraverts are 75%. If this were the case, your jury panel would almost always be made up of a majority of extraverts. Thankfully, there is actually no data to support that assertion. The latest actual figures from a Myers-Briggs 1998 manual show we are pretty much evenly divided between introverts and extraverts. It is simply a matter of where we find ourselves on the continuum (how introverted or how extraverted].

So when you want a free will/moral responsibility [and likely more punitive] juror, it won’t hurt to see just which jurors are the social butterflies on the panel.


Schulz E, Cokely ET, & Feltz A (2011). Persistent bias in expert judgments about free will and moral responsibility: A test of the expertise defense. Consciousness and cognition PMID: 21596586


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