Knowledge is power? Outcome probability information impairs detection of deceptive intent

The benefits and costs of prior expectations that are (i.e., congruent) or are not in harmony (i.e., incongruent) with action outcomes appear to be balanced; however, researchers have yet to examine the influence on skilled detection of deception. In this study we investigated whether response bias resulting from probability information (a) is stronger for low-skilled than high-skilled participants, (b) is stronger for deceptive actions than genuine actions, and (c) impairs the discriminability of genuine and deceptive actions. High-skilled (n = 15) and low-skilled (n = 15) soccer players responded to life-sized projected video clips showing an oncoming opponent taking the ball to their left or right, with or without a deceptive ‘stepover’ action. Three probability conditions were used with respect to outcome direction: 50/50, 67/33, and 83/17. Participants responded by stepping on one of two corresponding pressure mats, as if attempting to intercept the player. Response accuracy for genuine and deceptive actions was used to generate measures of bias (c) and sensitivity (d’). The results confirmed stronger probability bias for deceptive actions than genuine ones, and for low-skilled than high-skilled participants. Congruence between high outcome probability and the direction of the fake significantly enhanced the effectiveness of the deceptive action. The study provides the first evidence that outcome probability information impairs skilled detection of deceptive intent.