More is better: Relative prevalence of multiple targets affects search accuracy.

In real-world searches such as airport baggage screening and radiological examinations, miss errors can be life threatening. Misses increase for additional targets after detecting an initial target, termed "subsequent search misses" (SSMs), and also when targets are more often absent than present, termed the low-prevalence effect. Real-world search tasks often contain more than one target, but the prevalence of these multitarget occasions varies. For example, a cancerous tumor sometimes coexists with a benign tumor and sometimes exists alone. This study aims to investigate how the relative prevalence of multiple targets affects search accuracy. Naive observers searched for all Ts (zero, one, or two) among Ls. In Experiment 1, SSMs occurred in small but not large set sizes, which may be explained by classic capacity limit effects such as the attentional blink and repetition blindness. Experiment 2 showed an interaction between SSMs and the relative prevalence of dual-target trials: Low prevalence of dual-target trials increased SSMs relative to high prevalence dual-target trials. The prevalence of dual-target trials did not affect accuracy on single-target trials. These results may provide a novel avenue for reducing misses by increasing the prevalence of instances with multiple targets. Future efforts should take into account the relative prevalence of multiple targets to effectively reduce life-threatening miss errors.