Specification of multiple visual processes in metacontrast masking by means of individual differences

一种检查视觉刺激对感知和动作的处理的方法采用元对比掩蔽范例，其特征在于具有目标的两个刺激序列和不与目标刺激重叠的后续掩蔽刺激。当目标和掩蔽之间的刺激起始不同步(SOA)不同时，掩蔽效应的时间过程导致掩蔽函数在某些条件下遵循U形，但在其他条件下仅随刺激起始异步而增加。然而，尽管条件相同，我们发现能见度函数在U形函数和递增函数之间整个范围内变化的个体之间存在稳定的差异。这一发现挑战了所有假设单一机制的元对比掩蔽的描述。个体差异更支持元对比掩蔽的多加工解释。能见度函数的因子分析表明，至少可以区分三个潜在变量。我们假设这些潜在变量指向三个过程，这三个过程根据各自不同的权重对个别观察者的表现做出贡献。在拟议的项目中，我们希望通过比较元对比掩蔽的个体差异和其他功能可解释的实验条件下的个体差异，来确定这些过程的功能。我们假设了一个促进短SOA感知的整合过程，一个有助于提高中等SOA性能的运动感知过程，以及一个支持长SOA目标感知的分割过程。在六项研究中，我们希望研究与刺激轮廓、运动和深度相关的过程，以及两个刺激的时间整合如何导致元对比掩蔽中的个体差异。为了定位视觉系统中的过程，我们比较单视和双视刺激条件下的个体差异，并检查元对比中使用的刺激序列的电生理反应。这个项目可以举例说明个体差异如何对视觉处理的一般描述做出贡献。我们期望这一方法有助于明确在元对比掩蔽中以加权组合方式对视觉感知做出贡献的过程的功能。

One approach to examine the processing of visual stimuli for perception and action employs the metacontrast masking paradigm that is characterized by at two-stimulus sequence with a target and a following masking stimulus which does not overlap with the target stimulus. When the stimulus onset asynchrony (SOA) between target and mask is varied, the time course of masking effects results in a masking function which follows a u-shape in some conditions but simply increases with SOA in other conditions. Despite identical conditions, however, we have found stable differences between individuals with visibility functions that varied in the entire range between u-shaped and increasing functions. This finding challenges all accounts of metacontrast masking that assume a single mechanism. The individual differences rather support multi-process accounts of metacontrast masking. Factor analyses of the visibility functions suggest that at least three latent variables can be distinguished. We assume that these latent variables point to three processes which contribute according to an individually different weighting to the performance of individual observers. In the proposed project we want to specify these processes in their function by comparing individual differences in metacontrast masking with individual differences in other functional interpretable experimental conditions. We assume an integration processes which facilitates perception with short SOAs, a motion perception process that contributes to performance with intermediate SOAs, and a segmentation process which supports target perception with long SOAs. In six studies we want to examine how processes related to stimulus contour, motion and depth, as well as temporal integration of two stimuli contribute to individual differences in metacontrast masking. To localize processes in the visual system we compare individual differences in monoptic and dichoptic stimulus conditions and examine electrophysiological responses to the stimulus sequence used in metacontrast. This project can exemplify how individual differences can contribute to general accounts of visual processing. We expect that this approach helps to specify the function of the processes that contribute in a weighted combination to visual perception in metacontrast masking.