Friendly fire and the proportion of friends to foes

Losses of inhibitory control may be partly responsible for some friendly fire incidents. The Sustained Attention to Response Task (SART; Robertson, Manly, Andrade, Baddeley, & Yiend, 1997) may provide an appropriate empirical model for this. The current investigation aimed to provide an ecologically valid application of the SART to a small arms simulation and examine the effect of different proportions of enemy to friendly confederates. Seven university students engaged in a small arms simulation where they cleared a building floor using a near-infrared emitter gun, tasked with firing at confederates representing enemies and withholding fire to confederates representing friends. All participants completed three conditions which were differentiated by the proportion of enemies to friends present. As hypothesized, participants failed to withhold responses more often when the proportion of foes was higher, suggesting that a prepotent motor response routine had developed. This effect appeared to be disproportionately more substantial in the high foe condition relative to the others. Participants also subjectively reported higher levels of on-task focus as foe proportions increased, suggesting that they found this more mentally demanding. Future research could examine closer the nature of the performance reductions associated with high proportions of foes, as it appears that this is more complex than a simple linear relationship.