‘Liars are less detailed’ …So what? Comparing two recall instructions to detect deception within-subject

Most deception research provides between-subject results (e.g., liars give on average less detailed accounts), which might be of limited value for professionals evaluating credibility on an individual basis. This study examines the optimal instructions of a within-subject multiple recalls strategy to detect deception. A total of 110 participants, divided into a Lie and Truth group, were randomly placed into four interview conditions: two Basic report-everything instructions (1), a Basic recall followed by an Open depth instruction (2), a Basic recall followed by the Verifiability Approach and Information Protocol (3), and two recalls with the Verifiability Approach and Information Protocol (4). All recalls were coded for total details and verifiable details. Group (lie and truth) × Recall (first and second) was only significant in condition 3, with truth tellers providing more verifiable details in the second recall than the first. A simple within-subject decision rule was derived, allowing a 76.9% discrimination rate. Professionals can optimally evaluate credibility using two recalls (Basic recall followed by Verifiability Approach and Information Protocol) and observing the evolution of verifiable details.