Changes in visual computations across the visual field: depth and crowding

我们视野的中心（中央凹）具有最高的分辨细节（敏锐度）的能力，如果我们注意到周围有什么感兴趣的东西，我们会移动眼睛，使物体的图像福尔斯在中央凹上，而不是我们视网膜的外围部分。我们这样做是因为我们的视觉系统在远离中央凹的地方敏锐度很低。如果经常是令人惊讶的是，我们能够识别的字母很少，因为它们与中央凹的距离（偏心率）增加。 多年来，视觉科学家们研究了周边视觉，并证实当刺激物以越来越多的偏心度呈现时，视觉敏锐度福尔斯会下降。这可以通过让观察者注视计算机显示器上的一个点来完成，然后在外围闪烁刺激，这样他们就没有时间移动眼睛直接看它。然而，已经发现，在许多情况下，当外围呈现的刺激足够大时，（相对于中央凹标准放大），观察者可以像对呈现给中央凹的标准刺激一样准确地对放大的刺激做出判断。 多年来，这类实验中使用的刺激都是简单的几何形状（线条和字母），很少有人关注刺激放大是否能让我们发现物体的三维形状、人行走的方向甚至行走者的身份等微小差异。这里提出的大部分研究正是针对这类问题。具体来说，我们询问刺激放大是否允许我们对外围的3D形状做出与我们在中央凹处做出的判断一样准确的判断。我们问这种能力，无论是在视野中孤立的刺激，或在不同距离的侧翼项目包围，因为它是众所周知的，识别刺激在拥挤的背景是在外围比固定困难得多。虽然我们的兴趣是理论上的，但从长远来看，更好地了解周边视觉的能力将使我们能够更好地帮助那些因黄斑变性等疾病而失去中心凹视力的人。

The centre of our visual field (the fovea) has the highest ability to resolve fine details (acuity), and if we notice something of interest in our surroundings we will move our eyes so that the image of the object falls on the fovea, rather than some peripheral part of our retinas. We do this because our visual systems have low acuity away from the fovea. If is often surprising how few letters on a page we are able to identify as their distance from the fovea (eccentricity) increases. For many years vision scientists have studied peripheral vision and verified that visual acuity falls off as stimuli are presented at increasing eccentricities. This can be done by having observers fixate at a point on computer monitor, and then flashing a stimulus in the periphery so that they don't have time to move their eyes to look directly at it. It has been found, however, that in many cases, when peripherally presented stimuli are made sufficiently large (magnified relative to a foveal standard), observers can be as accurate at making judgments about the magnified stimuli as they are about the standard stimuli presented to the fovea. For many years the stimuli used in experiments of this sort have been simple geometric forms (lines and letters) and little attention has been paid to whether stimulus magnification allows us to detect small differences the the three-dimensional shapes of objects, the direction that person is walking or even the identity of walkers. A large portion of the research proposed here deals with exactly this kind of question. Specifically, we asked whether stimulus magnification permits us to make judgements about 3D shapes in the periphery that are as accurate as those we can make at the fovea. We ask about this ability both for stimuli isolated in the visual field, or surrounded by flanking items at varying distances, because it is well know that identifying stimuli in a crowded background is much harder in the periphery than at fixation. Although our interests are theoretical, in the long run a better understanding of the abilities of peripheral vision will put us in a better position to help those who have lost foveal vision because of diseases like macular degeneration.