Earwitness line-ups: effects of speech duration, retention interval and acoustic environment on identification accuracy

Abstract

An experiment was conducted to investigate the effects of retention interval, exposure duration and acoustic environment on speaker identification accuracy in voice line-ups. In addition, the relation between confidence assessments by participants and test assistant and identification accuracy was explored. A total of 361 participants heard a single target voice in one of four exposure conditions (short or long speech sample, recorded only indoors or indoors and outdoors). Half the participants were tested immediately after exposure to the target voice and half one week later. The results show that the target was correctly identified in 42% of cases. In the target-absent condition there were 51% false alarms. Acoustic environment did not affect identification accuracy. There was an interaction between speech duration and retention interval in the target-absent condition: after a one-week interval, listeners made fewer false identifications if the speech sample was long. No effects were found when participants were tested immediately. Only the confidence scores of the test assistant had predictive value. Taking the confidence score of the test assistant into account therefore increases the diagnostic value of the line-up.