Wu Chia-Chien, Kowler Eileen
Department of Psychology, Rutgers University, Piscataway, NJ, USA.
J Vis. 2013 Sep 18;13(11):11. doi: 10.1167/13.11.11.
Visual search requires sequences of saccades. Many studies have focused on spatial aspects of saccadic decisions, while relatively few (e.g., Hooge & Erkelens, 1999) consider timing. We studied saccadic timing during search for targets (thin circles containing tilted lines) located among nontargets (thicker circles). Tasks required either (a) estimating the mean tilt of the lines, or (b) looking at targets without a concurrent psychophysical task. The visual similarity of targets and nontargets affected both the probability of hitting a target and the saccade rate in both tasks. Saccadic timing also depended on immediate conditions, specifically, (a) the type of currently fixated location (dwell time was longer on targets than nontargets), (b) the type of goal (dwell time was shorter prior to saccades that hit targets), and (c) the ordinal position of the saccade in the sequence. The results show that timing decisions take into account the difficulty of finding targets, as well as the cost of delays. Timing strategies may be a compromise between the attempt to find and locate targets, or other suitable landing locations, using eccentric vision (at the cost of increased dwell times) versus a strategy of exploring less selectively at a rapid rate.
视觉搜索需要一系列的扫视运动。许多研究都集中在扫视决策的空间方面，而相对较少的研究（例如，Hooge和Erkelens，1999）考虑时间因素。我们研究了在搜索位于非目标（较粗的圆圈）中的目标（包含倾斜线条的细圆圈）时的扫视时间。任务要求要么（a）估计线条的平均倾斜度，要么（b）在没有同时进行心理物理学任务的情况下查看目标。目标和非目标的视觉相似性在两项任务中均影响命中目标的概率和扫视率。扫视时间也取决于即时条件，具体而言，（a）当前注视位置的类型（在目标上的停留时间比在非目标上更长），（b）目标的类型（在命中目标的扫视之前停留时间更短），以及（c）扫视在序列中的顺序位置。结果表明，时间决策考虑了找到目标的难度以及延迟的代价。时间策略可能是一种折衷，即在尝试使用周边视觉找到并定位目标或其他合适的着陆位置（以增加停留时间为代价）与以快速速率进行较少选择性探索的策略之间进行折衷。
