ABSTRACT
We investigated the neural signatures of expert decision making in the context of police training in a virtual reality-based shoot/don't shoot scenario. Police officers can use stopping force against a perpetrator, which may require using a firearm and each decision made by an officer to discharge their firearm or not has substantial implications. Therefore it is important to understand the cognitive and underlying neurophysiological processes that lead to such a decision. We used virtual reality-based simulations to elicit ecologically valid behaviour from Authorised Firearms Officers (AFOs) in the UK and matched novices in a Shoot/Don't Shoot task and recorded electroencephalography concurrently. We found that AFOs had consistently faster response times than novices, suggesting our task was sensitive to their expertise. To investigate differences in decision making processes under varying levels of threat and expertise, we analysed electrophysiological signals originating from the anterior cingulate cortex. In line with similar response inhibition tasks, we found greater increases in pre-response theta power when participants inhibited the response to shoot when under no threat as compared to shooting. Most importantly, we showed that when preparing against threat, theta power increase was greater for experts than novices, suggesting that differences in performance between experts and novices are due to their greater orientation towards threat. Additionally, shorter beta-rebounds suggest that experts were "ready for action" sooner. More generally, we demonstrate that investigation of expert decision making should incorporate naturalistic stimuli and an appropriate control group to enhance validity.Significance statement This study aims to unravel the complexities of how expertise affects neural processes during uncertain scenarios by investigating police decision making. We present our variant on shoot/don't shoot tasks which was co-developed with police instructors to allow graded levels of force to elicit realistic responses. We show that experts exhibit superior performance in this virtual reality-based task and that this is associated with greater modulation of frontal midline theta activity prior to a decision. Understanding the intricacies of police decision making-especially concerning the use of firearms-is vital to inform policy effectively. Further, the naturalistic imaging methods employed here hold broader significance for neuroscientists aiming to investigate real world behaviour.
ABSTRACT
A rotation stage was developed to allow the surface of bullet casings to be imaged under ultra-high vacuum (UHV) conditions using time-of-flight secondary ion mass spectrometry (ToF-SIMS). Experiments were performed over a period of seven months to determine how fingermarks deposited on the surface of Webley MkII revolver rounds change over time. Stitching software written in Python was used to combine image strips that were collected by performing ToF-SIMS analysis along the length of the revolver rounds. The ToF-SIMS analysis was performed by analysing a thin strip along the length of the casings, before rotating them through a few degrees and analysing a new strip. This process was repeated until the entire casing had been imaged. The resulting secondary ion images of the fingermarks were compared to optical images obtained from the same and similar rounds that had been exposed to cyanoacrylate fumes and subsequently stained using Basic Yellow 40 (BY40) dye. ToF-SIMS images were shown to display evidence of ridge and sweat pore level detail on samples that displayed no evidence of fingermarks when developed with cyanoacrylate and BY40. The effects of the curvature of the round casings on the morphology of fingermarks were also assessed. ToF SIMS images were compared to marks that had been deposited onto flat paper surfaces using ink. The distortions caused by differences in surface curvature and the deposition methods were found to be within acceptable limits.
Subject(s)
Copper , Zinc , Spectrometry, Mass, Secondary IonABSTRACT
Virtual reality (VR) provides an immersive environment in which a participant can experience a feeling of presence in a virtual world. Such environments generate strong emotional and physical responses and have been used for wide-ranging applications. The ability to collect functional neuroimaging data whilst a participant is immersed in VR would represent a step change for experimental paradigms; unfortunately, traditional brain imaging requires participants to remain still, limiting the scope of naturalistic interaction within VR. Recently however, a new type of magnetoencephalography (MEG) device has been developed, that employs scalp-mounted optically-pumped magnetometers (OPMs) to measure brain electrophysiology. Lightweight OPMs, coupled with precise control of the background magnetic field, enables participant movement during data acquisition. Here, we exploit this technology to acquire MEG data whilst a participant uses a virtual reality head-mounted display (VRHMD). We show that, despite increased magnetic interference from the VRHMD, we were able to measure modulation of alpha-band oscillations, and the visual evoked field. Moreover, in a VR experiment in which a participant had to move their head to look around a virtual wall and view a visual stimulus, we showed that the measured MEG signals map spatially in accordance with the known organisation of primary visual cortex. This technique could transform the type of neuroscientific experiment that can be undertaken using functional neuroimaging.
