Both academic and legal communities have cautioned that laypersons may be unduly persuaded by images of the brain and may fail to interpret them appropriately. While early studies confirmed this concern, a second wave of research was repeatedly unable to find evidence of such a bias. The newest wave of studies paints a more nuanced picture in which, under certain circumstances, a neuroimage bias reemerges. To help make sense of this discordant body of research, we highlight the contextual significance of understanding how laypersons' decision making is or is not impacted by neuroimages, provide an overview of findings from all sides of the neuroimage bias question, and discuss what these findings mean to public use and understanding of neuroimages.

Several highly-cited experiments have presented evidence suggesting that neuroimages may unduly bias laypeople’s judgments of scientific research. This finding has been especially worrisome to the legal community in which neuroimage techniques may be used to produce evidence of a person’s mental state. However, a more recent body of work that has looked directly at the independent impact of neuroimages on layperson decision-making (both in legal and more general arenas), and has failed to find evidence of bias. To help resolve these conflicting findings, this research uses eye tracking technology to provide a measure of attention to different visual representations of neuroscientific data. Finding an effect of neuroimages on the distribution of attention would provide a potential mechanism for the influence of neuroimages on higher-level decisions. In the present experiment, a sample of laypeople viewed a vignette that briefly described a court case in which the defendant’s actions might have been explained by a neurological defect. Accompanying these vignettes was either an MRI image of the defendant’s brain, or a bar graph depicting levels of brain activity–two competing visualizations that have been the focus of much of the previous research on the neuroimage bias. We found that, while laypeople differentially attended to neuroimagery relative to the bar graph, this did not translate into differential judgments in a way that would support the idea of a neuroimage bias.

Previous research on the relation between working memory capacity (WMC) and shooting behavior suggests that individuals with low working memory spans are more prone to shooting errors than are individuals with high working memory spans. The present study investigated how WMC interacts with the proportion of “shoot” to “don’t shoot” decisions to affect overall shooting performance. Participants were 186 undergraduate students who completed a series of complex span tasks, rated a series of negative photographs for valence and arousal, and then completed a computerized shooting task in which participants were shooting on 20%, 50%, or 80% of the trials. Results indicated that participants with high working memory spans outperformed participants with low working memory spans in all conditions. Participants also exhibited a greater tendency to inappropriately shoot as the proportion of shoot decisions increased. These results suggest that WMC and the proportion of shoot trials interact to affect shooting behavior.

This chapter examines the emerging use of neuroscience evidence in criminal trials and its influence on jury decision-making. It begins with a look at the prevalence of neuroscience expert evidence in criminal cases, finding a rapid increase in its use both in and outside of the United States. It then looks at the broader research on how the lay public is persuaded by neuroscience-derived information, followed by an examination of the relatively young literature on the specific (and often paradoxical) impact of neuroscience and neuroimagery on jurors’ judgments of criminal defendants. The chapter concludes with some caveats about the current state of neuroscience with respect to the legal system and some recommendations for future research.