Which statement best describes the effect of asking unanticipated questions on deception detection?

• A. Unanticipated questions reduce the advantage of rehearsed lies and improve detection.
• B. Unanticipated questions increase liars' cognitive load more than truth-tellers.
• C. Unanticipated questions have no effect on deception detection.
• D. Unanticipated questions cause truth-tellers to behave more deceptively.

Answer: (A)

Unanticipated questions test a liar’s ability to improvise, not just recite a rehearsed script. When someone fabricates a story, they often rely on a memorized sequence of details. Surprise prompts force them to generate new information on the spot, increasing cognitive strain and making inconsistencies more likely to appear. Truth-tellers, recounting real experiences, tend to respond more fluently and consistently even to unexpected prompts, so the gap between truth and deception grows. This is why unanticipated questions reduce the advantage of rehearsed lies and improve deception detection.

The idea that there’s no effect isn’t supported by research, and the notion that truth-tellers start behaving deceptively under surprise isn’t accurate. Focusing only on cognitive load without linking it to observable detection outcomes also doesn’t capture why these questions aid identification of deceit.