Nosewitness Identification: Effects of Lineup Size and Retention Interval

Abstract

Although canine identification of body odor (BO) has been widely used as forensic evidence, the concept of nosewitness identification by human observers was only recently put to the test. The results indicated that BOs associated with male characters in authentic crime videos could later be identified in BO lineup tests well above chance. To further evaluate nosewitness memory, we assessed the effects of lineup size (Experiment 1) and retention interval (Experiment 2), using a forced-choice memory test. The results showed that nosewitness identification works for all lineup sizes (3, 5, and 8 BOs), but that larger lineups compromise identification performance in similarity to observations from eye- and earwitness studies. Also in line with previous eye- and earwitness studies, but in disagreement with some studies on odor memory, Experiment 2 showed significant forgetting between shorter retention intervals (15 min) and longer retention intervals (1-week) using lineups of five BOs. Altogether this study shows that identification of BO in a forensic setting is possible and has limits and characteristics in line with witness identification through other sensory modalities.

The Effects of Emotional Visual Context on the Encoding and Retrieval of Body Odor Information

“…At retrieval, receivers immediately identified the target BO and only rated the perceptual features of the BOs after the identification (Alho et al, 2015), whereas in the present study, receivers only identified the target BO after providing the ratings to all the BOs included in the lineup. As a result, the time passed between encoding and retrieval may be slightly longer than 15 min, and in line with the findings by Alho et al (2016), incrementing the delay between encoding and retrieval may have a disruptive effect in the accuracy of the identification performance.…”

“…Indeed, a methodological change implemented in the present study may have increased the difficulty of the recognition task when compared to Alho et al (2015Alho et al ( , 2016 and consequently reduced the accuracy performance. At retrieval, receivers immediately identified the target BO and only rated the perceptual features of the BOs after the identification (Alho et al, 2015), whereas in the present study, receivers only identified the target BO after providing the ratings to all the BOs included in the lineup.…”

“…Thus, complex and hard to verbalize stimuli, such as BOs, may lead to impairments in the accuracy performance (Cain, 1979). If this were generally true, it would go against the evidence produced by Alho et al (2015Alho et al ( , 2016, who revealed a facilitation effect in the identification of the BO paired with a criminal video, with a recognition delay of up to 15 min. Another option is that the nature of the memory here used to correctly remember the BO is implicit in nature, and therefore explicitly questioning the participants on the recognition of the BO may not be ideal to reveal whether and how the odor information was encoded.…”

“…The results showed an enhanced memory performance for target BOs that were encoded under the arousing condition (Alho et al, 2015). However, the effects seemed to be short-lived (15 min; Alho et al, 2016), and no emotional manipulation was performed at retrieval. In previous studies (e.g., de Groot, Semin, & Smeets, 2014), the emotional context is manipulated to induce in the donors different emotional states, namely to directly affect BO production.…”

“…The previously collected BOs were presented in odor-free glass jars and constituted the target and foil odor stimuli (Alho et al, 2015(Alho et al, , 2016. Please note that the foils were four BOs of the same emotional tone of the target which were not presented at encoding.…”