Can We Trust Intuitive Jurors? Standards of Proof and the Probative Value of Evidence in Coherence‐Based Reasoning

• Author: Christoph Engel,Andreas Glöckner
• Date: 01 June 2013
• DOI: http://doi.org/10.1111/jels.12009
• Published date: 01 June 2013

Can We Trust Intuitive Jurors? Standards

of Proof and the Probative Value of

Evidence in Coherence-Based Reasoning

Andreas Glöckner and Christoph Engel*

Jury members are confronted with highly complex, ill-defined problems. Coherence-based

reasoning (Pennington & Hastie 1992; Simon 2004), which partially relies on intuitive-

automatic processing, empowers them to nonetheless make meaningful decisions. These

processes, however, have a downside. We tested possible negative effects in a set of studies.

Specifically, we investigated whether stricter standards of proof are suppressed by stronger

coherence shifts and whether the probative value of the evidence is properly taken into

account. We found that U.S. model jury instructions for preponderance of the evidence and

beyond a reasonable doubt influence conviction rates in the intended direction and are not

undermined by coherence shifts, although probabilistic estimations of these standards are

inappropriate. However, even massive changes in explicitly stated probabilities, while

holding the overall constellation of facts constant, did not influence conviction rates or the

estimated probability of conviction. We argue that reforms in legal procedure should focus

on measures to reduce the negative side effects of coherence-based reasoning in general but,

more specifically, to make probabilistic information better evaluable for decisionmakers

in law.

I. Introduction

Jury members face a daunting task. They have to make decisions based on multiple pieces

of probabilistic evidence. These pieces of information are usually contradictory, essentially

always incomplete, presented in multiple formats (making them hard to compare and

integrate), and introduced by parties clearly intending to bias the jury. Explicitly handling

all this information according to normative standards, including properly assessing how

individual pieces of evidence interact, is usually not possible given severe limitations of

deliberate cognitive resources (Simon 1955). How do jury members then make meaningful

decisions? There is mounting evidence that most people do not mathematically integrate

evidence. Their behavior is better explained by sense making (Pennington & Hastie

*Address correspondence to Andreas Glöckner, Georg-Elias-Müller-Institute for Psychology, Georg-August-University

Göttingen, Gosslerstrasse 14, D-37073 Göttingen, Germany; email: gloeckner@coll.mpg.de. Glöckner is Professor of

Psychological Assessment, Judgment and Decision Making at the Georg-Elias-Müller-Institute for Psychology, Georg-

August-University Göttingen and head of the research group Intuitive Experts at the Max Planck Institute for

Research on Collective Goods, Bonn; Engel is Director of the Max Planck Institute for Research on Collective Goods,

Bonn.

The authors thank Dan Simon and Jeffrey Rachlinski for helpful comments.

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Journal of Empirical Legal Studies

Volume 10, Issue 2, 230–252, June 2013

230

1991:519) and constructing coherent stories from the evidence. People are storytellers, not

meter readers. Jurors attempt to create complete narratives from the pieces of evidence

they hear (Pennington & Hastie 1986, 1988, 1993).

In a similar vein, parallel constraint satisfaction (PCS) models (Glöckner & Betsch

2008b; Holyoak & Simon 1999; Thagard & Millgram 1995) postulate that when decision-

makers actively construct coherent mental representations of the situation, they thereby

unconsciously modify their perception of the evidence. People reason bi-directionally. Not

only do they construct an interpretation from the evidence but they also reason backward

from possible interpretations to the evidence. In this cognitive process, the original infor-

mation is systematically distorted (Holyoak & Simon 1999; Simon 2004; Simon et al. 2001,

2004b). It has been shown that different interpretations of the evidence are weighed against

each other, leading to a progressive radicalization of the evidence. Information supporting

the favored interpretation is highlighted, whereas the perceived importance or reliability of

information that contradicts this interpretation is reduced. These coherence shifts (also

referred to as coherence effects or predecisional information distortion) seem to be a fairly

widespread phenomenon (e.g., DeKay et al. 2009; Russo et al. 1996). They have not only

been observed for legal decisions (e.g., Engel & Glöckner in press; Holyoak & Simon 1999;

Simon 2004; Simon et al. 2004b) but it has, for example, also been reported that (1)

persons distort their perceptions of the attributes when selecting between apartments

(Simon et al. 2004a), (2) participants reassess the credibility of well-known weather fore-

casts when making their own prediction (Glöckner et al. 2010:Exps. 1, 2), and (3) subjects

even revalue the predictive power of relatively subtle cues (e.g., is the city a state capital or

not?) when asked to compare city sizes (Glöckner et al. 2010:Exp. 3).

From a legal perspective, decision making by way of storytelling and parallel con-

straint satisfaction is worrisome. Studies show that the underlying information distortions

induce persons to be overly confident in their judgments, mainly because conflicting

evidence is devalued (Simon et al. 2004b). Furthermore, appellate courts might give too

little weight to the influence of inadmissible evidence on trial court decisions (harmless

error analysis) if they rely on a guilt-focused approach, that is, if they are content with

showing that the unchallenged evidence provides sufficient grounds for conviction. Parallel

constraint satisfaction makes it likely that the inadmissible evidence has nonetheless indi-

rectly influenced the assessment of the remaining evidence (Simon 2004:575).

Further problems might result from this specific kind of information processing and

are explored in this article. First, since persons do not compare probabilities but construct

overall mental representations, they may be insufficiently sensitive to changes in the pro-

bative value of the evidence. This should particularly be the case if they have no good

standards against which to compare specific pieces of evidence (Hsee 1996; see also Slovic

et al. 2002). For example, when constructing their mental representations of the case,

persons may recognize that eyewitnesses are notoriously unreliable, but they might not

differentiate between cases in which the witness states she is 80 percent sure as opposed to

99 percent. Second, parallel constraint satisfaction might override the differences between

standards of proof. Specifically, persons could suppress stricter standards by larger coher-

ence shifts. Initial evidence for this argument is provided by research indicating that several

versions of standard of proof instructions do not influence conviction rates (Kagehiro

Can We Trust Intuitive Jurors? 231