Effects of presentation format and instructions on the ability of people with intellectual disability to identify faces.

The aim of this work was to analyze the effect of presentation format and instructions on the ability of people with intellectual disability to identify individuals they did not know and had seen only briefly. With this objective in mind, 2 groups of subjects with mild to moderate intellectual disability were shown a photograph of a person and, after a distracting task, were asked to identify that person in 2 line-ups (target-absent and target-present) with 6 photographs each, where 2 types of instructions (neutral vs specific, between-subject design) and 2 presentation formats (simultaneous vs sequential, within-subject design) for the line-up photographs were used. Each subject completed 4 trials. The results showed that, generally speaking, people with intellectual disability were capable of distinguishing the face of a person previously seen under all these conditions. There was a significantly higher incidence of false alarms, however, when the photographs were presented sequentially and when specific instructions were not given. With specific instructions designed to lessen the social desirability effect and increase motivation for the task, false alarms on the target-absent line-up were reduced. The results were discussed with a view to their applicability in legal and law enforcement contexts.