How fixation durations are related to the functional visual field and attentional guidance

我们每天都在我们的环境中搜索物品，但当医生在X光片上搜索结节或机场安检人员在随身行李中搜索危险物品时，搜索过程的准确性和速度变得至关重要。如果我们知道搜索目标的视觉特征(例如，在停车点搜索一辆蓝色汽车)，就会发生“引导式搜索”。则视觉系统被设置为对具有该特征的项目进行优先排序，使得在搜索期间(例如，当红色和绿色汽车不被检查为可能的目标候选时)，不需要顺序地关注每个项目。视觉搜索过程中引导的一个制约因素是眼睛的视网膜不均质性：如果我们在空白的桌面上搜索关键字，我们通常可以立即找到它，甚至在我们的眼角也是如此。然而，如果桌面杂乱无章，充满了让人分心的东西，我们通常必须在不同的位置进行多次凝视才能找到钥匙。也就是说，作为一般规则，视觉处理变得不那么可靠，物品离中央注视越远，视野中的物品越多。能够在注视中心附近可靠地检测到目标的视野区域被称为功能视野(FVF)，如果搜索到困难的目标，它将缩小。影响搜索难度的两个重要因素是干扰物和目标之间的相似性，以及干扰物的异质性。这项拟议的项目首先对凝视注视持续时间如何受到这两个组成部分的影响进行了更深入的研究。由此得出的结果将成为项目中将要建立的一种创新方法的基础，该方法将在参与者在屏幕上执行标准视觉搜索任务时测量FVF的大小。虽然目前最先进的方法模拟了在搜索过程中遮挡外围视觉输入的凝视应急聚光灯，但该项目的方法产生了一种替代方法来测量FVF大小，而不需要这种可能影响搜索行为的操作。重要的是，新方法揭示了在搜索过程中哪些注视是空间引导的，并且可以应用于搜索简单的人工刺激，并且潜在地也可以应用于搜索复杂的场景或射线照片，其中很难确定干扰物的数量。然而，在实验中，参与者搜索不同视觉特征尺寸的目标，并通过与其他方法的比较来估计FVF的大小，这是拟议项目的目的，因此有必要进行进一步的检查。

Every day we search for items in our environment, but the accuracy and the speed of the search process become critical when medical doctors search for nodules on radiographs or when airport security screeners search for dangerous items in the carry-on baggage. A “guided search” occurs if we know the visual features of the search target (e.g., in search for a blue car at the parking spot). Then the visual system is set to prioritize items with that features such that not every item has to be attended serially during search (e.g., when red and green cars are not inspected as possible target candidates). A constraining component for guidance in visual search processes is the retinal inhomogeneity of the eyes: If we search for a key on an empty desktop, we can often find it immediately, even at the corner of our eye. However, if the desktop is messy and full of distracting items, we usually must perform multiple gaze fixations at different locations to find the key. That is, as a general rule, visual processing becomes less reliable, the further away an item is from the central fixation, and the more items are in the visual field. The visual area within which a target can reliably be detected around the center of fixation is called the functional visual field (FVF) and it shrinks if a difficult target is searched for. Two important components that affect search difficulty are the similarity between distractors and the target, as well as the heterogeneity of the distractors. The proposed project begins with the closer investigation of how gaze fixation durations are affected by the two of these components. The resulting findings will be the basis for an innovative method that is going to be established in the project in order to measure the size of the FVF when participants perform standard visual search tasks on a screen. While current state-of-the-art methods simulate gaze contingent spotlights which obscure the peripheral visual input during search, the method of the project yields an alternative to measure the FVFs size without such a manipulation that may affect search behaviour. Importantly, the new method reveals which fixations are spatially guided during the search course and can be applied in search for simple, artificial stimuli, and potentially also in search through complex scenes or radiographs where it is difficult to define the number of distractors. However, further examination is necessary by the application on experiments where participants search for targets of different visual feature dimensions and by comparisons with other methods to estimate the FVF’s size, which is the purpose of the proposed project.