Grubert Anna, Eimer Martin
Birkbeck, University of London.
J Cogn Neurosci. 2016 Feb;28(2):319-32. doi: 10.1162/jocn_a_00898. Epub 2015 Oct 21.
Finding target objects among distractors in visual search display is often assumed to be based on sequential movements of attention between different objects. However, the speed of such serial attention shifts is still under dispute. We employed a search task that encouraged the successive allocation of attention to two target objects in the same search display and measured N2pc components to determine how fast attention moved between these objects. Each display contained one digit in a known color (fixed-color target) and another digit whose color changed unpredictably across trials (variable-color target) together with two gray distractor digits. Participants' task was to find the fixed-color digit and compare its numerical value with that of the variable-color digit. N2pc components to fixed-color targets preceded N2pc components to variable-color digits, demonstrating that these two targets were indeed selected in a fixed serial order. The N2pc to variable-color digits emerged approximately 60 msec after the N2pc to fixed-color digits, which shows that attention can be reallocated very rapidly between different target objects in the visual field. When search display durations were increased, thereby relaxing the temporal demands on serial selection, the two N2pc components to fixed-color and variable-color targets were elicited within 90 msec of each other. Results demonstrate that sequential shifts of attention between different target locations can operate very rapidly at speeds that are in line with the assumptions of serial selection models of visual search.
在视觉搜索显示中，从干扰项中找到目标物体通常被认为是基于对不同物体之间注意力的顺序移动。然而，这种序列性注意力转移的速度仍存在争议。我们采用了一项搜索任务，该任务鼓励在同一搜索显示中依次将注意力分配到两个目标物体上，并测量N2pc成分，以确定注意力在这些物体之间移动的速度。每个显示包含一个具有已知颜色的数字（固定颜色目标）和另一个数字，其颜色在不同试验中不可预测地变化（可变颜色目标），以及两个灰色干扰数字。参与者的任务是找到固定颜色的数字，并将其数值与可变颜色数字的数值进行比较。对固定颜色目标的N2pc成分先于对可变颜色数字的N2pc成分出现，这表明这两个目标确实是按照固定的序列顺序被选择的。对可变颜色数字的N2pc成分在对固定颜色数字的N2pc成分出现后约60毫秒出现，这表明注意力可以在视野中的不同目标物体之间非常迅速地重新分配。当搜索显示持续时间增加，从而放宽对序列选择的时间要求时，对固定颜色和可变颜色目标的两个N2pc成分在彼此90毫秒内被诱发。结果表明，不同目标位置之间注意力的序列转移可以以与视觉搜索序列选择模型假设相符的速度非常迅速地进行。
