TY - JOUR
T1 - Why do we miss rare targets? Exploring the boundaries of the low prevalence effect
AU - Rich, Anina N.
AU - Kunar, Melina A.
AU - Van Wert, Michael J.
AU - Hidalgo-Sotelo, Barbara
AU - Horowitz, Todd S.
AU - Wolfe, Jeremy M.
PY - 2008/11/24
Y1 - 2008/11/24
N2 - Observers tend to miss a disproportionate number of targets in visual search tasks with rare targets. This 'prevalence effect' may have practical significance since many screening tasks (e.g., airport security, medical screening) are low prevalence searches. It may also shed light on the rules used to terminate search when a target is not found. Here, we use perceptually simple stimuli to explore the sources of this effect. Experiment 1 shows a prevalence effect in inefficient spatial configuration search. Experiment 2 demonstrates this effect occurs even in a highly efficient feature search. However, the two prevalence effects differ. In spatial configuration search, misses seem to result from ending the search prematurely, while in feature search, they seem due to response errors. In Experiment 3, a minimum delay before response eliminated the prevalence effect for feature but not spatial configuration search. In Experiment 4, a target was present on each trial in either two (2AFC) or four (4AFC) orientations. With only two response alternatives, low prevalence produced elevated errors. Providing four response alternatives eliminated this effect. Low target prevalence puts searchers under pressure that tends to increase miss errors. We conclude that the specific source of those errors depends on the nature of the search.
AB - Observers tend to miss a disproportionate number of targets in visual search tasks with rare targets. This 'prevalence effect' may have practical significance since many screening tasks (e.g., airport security, medical screening) are low prevalence searches. It may also shed light on the rules used to terminate search when a target is not found. Here, we use perceptually simple stimuli to explore the sources of this effect. Experiment 1 shows a prevalence effect in inefficient spatial configuration search. Experiment 2 demonstrates this effect occurs even in a highly efficient feature search. However, the two prevalence effects differ. In spatial configuration search, misses seem to result from ending the search prematurely, while in feature search, they seem due to response errors. In Experiment 3, a minimum delay before response eliminated the prevalence effect for feature but not spatial configuration search. In Experiment 4, a target was present on each trial in either two (2AFC) or four (4AFC) orientations. With only two response alternatives, low prevalence produced elevated errors. Providing four response alternatives eliminated this effect. Low target prevalence puts searchers under pressure that tends to increase miss errors. We conclude that the specific source of those errors depends on the nature of the search.
UR - http://www.scopus.com/inward/record.url?scp=56749107401&partnerID=8YFLogxK
U2 - 10.1167/8.15.15
DO - 10.1167/8.15.15
M3 - Article
C2 - 19146299
AN - SCOPUS:56749107401
VL - 8
SP - 1
EP - 17
JO - Journal of Vision
JF - Journal of Vision
SN - 1534-7362
IS - 15
M1 - 15
ER -