Opposing experts, relative judgments and the reemergence of the neuroimage bias

There is conflicting evidence regarding whether a biasing effect of neuroscientific evidence exists. Early research warned of such bias, but more recent papers dispute such claims, with some suggesting a bias only occurs in situations of relative judgment, but not in situations of absolute judgment. The current studies examined the neuroimage bias within both criminal and civil court case contexts, specifically exploring if a bias is dependent on the context in which the neuroimage evidence is presented (i.e. a single expert vs. opposing experts). In the first experiment 408 participants read a criminal court case summary in which either one expert witness testified (absolute judgment) or two experts testified (relative judgment). The experts presented neurological evidence in the form of functional magnetic resonance imaging (fMRI) data and the evidence type varied between a brain image and a graph. A neuroimage bias was found, in that jurors who were exposed to two experts were more punitive when the prosecution presented the image and less punitive when the defense did. In the second experiment 240 participants read a summary of a civil court case in which either a single expert witness testified or two experts testified. The experts presented fMRI data to support or refute a claim of chronic pain and the evidence type again varied between image and graph. The expected neuroimage bias was not found, in that jurors were more likely to find in favor of the plaintiff when either side proffered the image, but more likely to find for the defense when only graphs were offered by the experts. These findings suggest that the introduction of neuroimages as evidence may affect jurors punitiveness in criminal cases, as well as liability decisions in civil cases and overall serves to illustrate that the influence of neuroscientific information on legal decision makers is more complex than originally thought.