Cameron, E.L., Tai, J.C., Eckstein,
M.P. & Carrasco, M. (2004). Signal detection theory applied to three
visual search tasks: Identification, Yes/No detection and localization.
Spatial Vision. 17, 295-325.
Adding distracters to a display impairs performance on visual tasks (i.e.
the set-size effect). While keeping the display characteristics constant,
we investigated this effect in three tasks: 2 target identification, yes-no
detection with 2 targets and 8-alternative localization. A Signal Detection
Theory (SDT) model, tailored for each task, accounts for the set-size
effects observed in identification and localization tasks, and slightly
under-predicts the set-size effect in a detection task. Given that sensitivity
varies as a function of spatial frequency (SF), we measured performance
in each of these three tasks in neutral and peripheral precue conditions
for each of six spatial frequencies (0.5 - 12 cpd). For all spatial frequencies
tested, performance on the three tasks decreased as set size increased
in the neutral precue condition, and the peripheral precue reduced the
effect. Larger set-size effects were observed at low SFs in the identification
and localization tasks. This effect can be described using the SDT model,
but was not predicted by it. For each of these tasks we also established
the extent to which covert attention, modulates performance across a range
of set sizes. A peripheral precue substantially diminished the set-size
effect and improved performance, even at set size 1. These results provide
support for distracter exclusion, and suggest that signal enhancement
may also be a mechanism by which covert attention can impose its effect.
Keywords:Visual search; signal detection theory; transient covert attention;
yes/no detection; discrimination; localization.