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

我们每天都在搜索周围环境中的物品，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，在停车场寻找一辆蓝色的车）。然后，视觉系统被设置为对具有该特征的项目进行优先级排序，使得在搜索期间不必连续关注每个项目（例如，当红色和绿色汽车不作为可能的目标候选被检查时）。视觉搜索过程中的一个限制因素是眼睛的视网膜不均匀性：如果我们在空桌面上搜索一个键，我们通常可以立即找到它，甚至在我们的眼角。然而，如果桌面很乱，到处都是分散注意力的东西，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，视觉处理变得不太可靠，项目离中心注视越远，视野中的项目越多。在注视中心周围能够可靠地检测到目标的视觉区域被称为功能性视野（FVF），如果搜索困难的目标，则功能性视野缩小。影响搜索难度的两个重要因素是干扰项与目标之间的相似性以及干扰项的异质性。拟议的项目开始密切调查如何注视注视持续时间的影响，这两个组件。由此产生的结果将是一种创新方法的基础，该方法将在该项目中建立，以测量当参与者在屏幕上执行标准视觉搜索任务时FVF的大小。虽然目前最先进的方法模拟凝视偶然聚光灯，在搜索过程中模糊的周边视觉输入，该项目的方法产生了一种替代方法来测量FVF的大小，而没有这样的操纵，可能会影响搜索行为。重要的是，新的方法揭示了在搜索过程中，哪些注视点是空间引导的，并且可以应用于搜索简单的人工刺激，并且可能也可以应用于搜索复杂的场景或射线照片，其中难以定义干扰物的数量。然而，进一步的检查是必要的应用程序的实验中，参与者搜索不同的视觉特征尺寸的目标，并通过与其他方法的比较，以估计FVF的大小，这是拟议的项目的目的。

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.