The dud effect: adding highly dissimilar fillers increases confidence in lineup identifications

Area of Science:

• Cognitive Psychology
• Forensic Psychology
• Decision Making

Background:

• The dud-alternative effect describes increased confidence in a choice when surrounded by implausible options.
• This effect may influence eyewitness identification accuracy and confidence in legal settings.

Purpose of the Study:

• To investigate if the dud-alternative effect impacts eyewitness confidence in lineup identification.
• To determine the mechanisms behind this confidence inflation and its boundary conditions.

Main Methods:

• Four studies (N=665) examined the impact of highly dissimilar fillers (duds) in eyewitness lineups.
• Participants made identification decisions, and confidence ratings were analyzed in relation to filler dissimilarity.

Main Results:

• The presence of highly dissimilar fillers significantly inflated eyewitnesses' confidence in mistaken identifications.
• Evidence suggests duds increase confidence by inflating the perceived similarity of other lineup members to the perpetrator.
• The effect was observed under specific conditions across the studies.

Conclusions:

• Dissimilar lineup fillers are not inert and can actively bias eyewitness confidence.
• The dud-alternative effect demonstrates a potential flaw in standard lineup procedures that can inflate confidence in inaccurate identifications.