Clarifying the effects of sequential item presentation in the police lineup task

Previous research has reported diverging patterns of results with respect to discriminability and response bias when comparing the simultaneous lineup to two different lineup procedures in which items are presented sequentially, the sequential stopping rule lineup and the UK lineup. In a single large sample experiment, we compared discriminability and response bias in six-item photographic lineups presented either simultaneously, sequentially with a stopping rule, or sequentially requiring two full laps through the items before making an identification and including the ability to revisit items, analogous to the UK lineup procedure. Discriminability was greater for the simultaneous lineup compared to the sequential stopping rule lineup, despite a non-significant difference in empirical discriminability between the procedures. There was no significant difference in discriminability when comparing the simultaneous lineup to the sequential two lineup and the sequential two lap lineup to the sequential stopping rule lineup. Responding was most lenient for the sequential two lap lineup, followed by the simultaneous lineup, followed by the sequential lineup. These results imply that sequential item presentation may not exert a large effect in isolation on discriminability and response bias. Rather, discriminability and response bias in the sequential stopping rule lineup and UK lineup result from the interaction of sequential item presentation with other aspects of these procedures.