Iterative Models in Figure-Ground Perception: Tests and Challenges

图形-背景感知中的迭代模型：测试和挑战

• 批准号: 0960529
• 负责人: Mary Peterson
• 金额: $ 44.42万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-06-15 至 2014-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0960529&HistoricalAwards=false
• 关键词: Iterative; Models; Figure; Ground; Perception

Visual perception seems trivially easy. Nevertheless, it has long withstood the attempts of both computer scientists and vision scientists to crack its code, most likely because past theories were based predominantly on conscious vision. In order for perceivers to experience a coherent visual world, perceptual input must be organized into separate objects, or "figures." As part of this process, the brain decides where a figure lies with respect to every border between two contiguous regions of space. Consider a vertical border, for instance. The brain decides whether that border is a boundary for a figure lying on the left or the right. When the border is perceived as a boundary of a figure lying on the left, the region on the right seems simply to continue behind the figure at the border; no shape is perceived there. These "figure-ground" decisions are made outside of conscious awareness. Because of this, it is extremely difficult to investigate the mechanisms that produce figure-ground perception. An important, unanswered, question is whether figure-ground perception is accomplished via fast, feed-forward mechanisms or whether iterative mechanisms involving feedback from higher processing levels are involved. In feed-forward models, the input is processed in successive stages until a coherent percept emerges. In iterative models, feed-forward processing is not sufficient; feedback from higher to lower levels is necessary to create the percept.Mary Peterson and her colleagues at the University of Arizona have designed visual displays that allow them to investigate this question. One display type is a small symmetric, bounded silhouette lying on a larger ground. Portions of familiar shapes are hidden along the groundside of the silhouette's border; these shapes are not perceived consciously, only the shape of the enclosed silhouette is perceived consciously. (The classic "face-vase illusion" is an example of this.) Previous experiments have shown that the shape of the hidden object is suppressed when it is not perceived, supporting the view that figure-ground perception results from inhibitory competition between shapes that might be seen on opposite sides of a border; the winner is perceived as the shaped figure, whereas the loser is suppressed and the portion of space where it might have been seen is perceived as a shapeless ground. These displays are designed to isolate competition at the shape processing stage. Dr. Peterson and colleagues will also conduct a series of experiments which test whether suppression can be observed at lower levels where individual parts are represented and at higher levels where shape descriptions ("semantics") are represented. According to a feed-forward account, suppression of the losing shape would prevent access to its semantics; hence, no effects should be evident at higher levels. Without feedback, no effects should be evident at lower, part-processing, levels either. An iterative view could account for suppression at lower and/or higher levels by assuming that the outcome of the between-shape competition was relayed to higher and lower levels. Thus the proposed experiments will adjudicate between these competing views of how perception occurs. The researchers will also attempt to identify the processes involved in segregating figures from grounds in crowded real-world scenes. The perception of these more complex displays constitutes a challenge to current iterative models of figure-ground perception. The planned research will provide a foundation for neurophysiological experiments and formal computational models of vision and will contribute to our understanding of the temporal and spatial dynamics of shape perception.

视觉感知似乎很简单。尽管如此，它长期以来经受住了计算机科学家和视觉科学家破解其代码的尝试，很可能是因为过去的理论主要基于有意识的视觉。为了让感知者体验一个连贯的视觉世界，感知输入必须被组织成单独的对象或“图形”。“作为这个过程的一部分，大脑决定一个图形相对于两个相邻空间区域之间的每个边界的位置。例如，考虑垂直边界。大脑决定这个边界是一个躺在左边还是右边的图形的边界。当边界被感知为左侧图形的边界时，右侧区域似乎只是在边界处的图形后面延续;那里没有形状。这些“图形-背景”的决定是在意识之外做出的。正因为如此，研究产生图形-背景知觉的机制是极其困难的。一个重要的，未回答的问题是，图形背景感知是否是通过快速，前馈机制或迭代机制，涉及来自更高的处理水平的反馈。在前馈模型中，输入在连续的阶段中被处理，直到出现相干的接收。 在迭代模型中，前馈处理是不够的;从更高到更低的层次的反馈是必要的，以创建一个新的概念。亚利桑那大学的玛丽彼得森和她的同事设计了视觉显示，使他们能够研究这个问题。一种显示类型是一个小的对称，有界的轮廓躺在一个较大的地面。熟悉形状的部分被隐藏在轮廓边界的地面沿着;这些形状不会被有意识地感知到，只有封闭轮廓的形状被有意识地感知到。(The经典的“脸-花瓶错觉”就是一个例子。先前的实验表明，隐藏物体的形状在未被感知时会受到抑制，这支持了图形-背景感知是由可能在边界两侧看到的形状之间的抑制竞争引起的观点;赢家被感知为有形状的图形，而失败者被抑制，可能被看到的空间部分被感知为无形状的背景。这些显示器被设计成在形状加工阶段隔离竞争。彼得森博士和他的同事们还将进行一系列实验，测试抑制是否可以在代表各个部分的较低水平和代表形状描述（“语义”）的较高水平上观察到。 根据前馈解释，对丢失形状的抑制将阻止对其语义的访问;因此，在更高的级别上不应该有明显的影响。没有反馈，在较低的部分处理水平上也不会有明显的效果。一个迭代的观点可以通过假设形状间竞争的结果被传递到更高和更低的水平来解释在更低和/或更高水平的抑制。因此，拟议中的实验将在这些关于感知如何发生的相互竞争的观点之间做出裁决。 研究人员还将试图确定在拥挤的现实世界场景中将人物与地面分离的过程。这些更复杂的显示器的感知构成了对当前图形-背景感知的迭代模型的挑战。 计划中的研究将为神经生理学实验和视觉的正式计算模型提供基础，并将有助于我们理解形状感知的时间和空间动态。