Cost and benefit of a new instruction for the cognitive interview: the open depth instruction

The quality and the quantity of information recalled by eyewitnesses during a criminal investigation is of crucial importance. To increase the volume of details recalled during an interview, the cognitive interview recommends using various retrieval strategies to enhance recall. We tested a new retrieval instruction, the open depth (OD) instruction. The efficacy of this new instruction was assessed with the number of unit of information and the accuracy rate. We also assessed the cost-and-benefit of this new instruction with measures of repetition. Students watched a video of a simulated robbery and participated later in face-to-face interviews. In Study 1 (N=60), the cognitive interview using the OD instruction increased recall compared to the interview using the change of perspective (CP) instruction, without affecting the accuracy rate. The redundancy rate was higher with the OD instruction than with the CP instruction. In Study 2 (N=40), the OD instruction generated more new information without affecting the accuracy rate than the interview using motivated recall (MR) instruction. The repeated information to new information ratio was lower with the OD instruction than with the MR instruction. The advantages of the OD instruction for investigative interviewing purposes are discussed.