Department of Psychology, American University, Washington, DC, United States of America.
PLoS One. 2010 Oct 13;5(10):e13296. doi: 10.1371/journal.pone.0013296.
The human visual system does not treat all parts of an image equally: the central segments of an image, which fall on the fovea, are processed with a higher resolution than the segments that fall in the visual periphery. Even though the differences between foveal and peripheral resolution are large, these differences do not usually disrupt our perception of seamless visual space. Here we examine a motion stimulus in which the shift from foveal to peripheral viewing creates a dramatic spatial/temporal discontinuity.
METHODOLOGY/PRINCIPAL FINDINGS: The stimulus consists of a descending disk (global motion) with an internal moving grating (local motion). When observers view the disk centrally, they perceive both global and local motion (i.e., observers see the disk's vertical descent and the internal spinning). When observers view the disk peripherally, the internal portion appears stationary, and the disk appears to descend at an angle. The angle of perceived descent increases as the observer views the stimulus from further in the periphery. We examine the first- and second-order information content in the display with the use of a three-dimensional Fourier analysis and show how our results can be used to describe perceived spatial/temporal discontinuities in real-world situations.
CONCLUSIONS/SIGNIFICANCE: The perceived shift of the disk's direction in the periphery is consistent with a model in which foveal processing separates first- and second-order motion information while peripheral processing integrates first- and second-order motion information. We argue that the perceived distortion may influence real-world visual observations. To this end, we present a hypothesis and analysis of the perception of the curveball and rising fastball in the sport of baseball. The curveball is a physically measurable phenomenon: the imbalance of forces created by the ball's spin causes the ball to deviate from a straight line and to follow a smooth parabolic path. However, the curveball is also a perceptual puzzle because batters often report that the flight of the ball undergoes a dramatic and nearly discontinuous shift in position as the ball nears home plate. We suggest that the perception of a discontinuous shift in position results from differences between foveal and peripheral processing.
人类视觉系统不会平等对待图像的所有部分：落在中央凹的图像中央部分，其处理分辨率高于落在视觉外围的部分。尽管中央凹和外围分辨率之间的差异很大，但这些差异通常不会破坏我们对无缝视觉空间的感知。在这里，我们研究了一种运动刺激，其中从中央凹到外围观察的转变会产生显著的空间/时间不连续性。
方法/主要发现：该刺激由一个下降的圆盘（全局运动）和一个内部移动的光栅（局部运动）组成。当观察者在中央观察圆盘时，他们会感知到全局和局部运动（即观察者会看到圆盘的垂直下降和内部旋转）。当观察者在边缘观察圆盘时，内部部分看起来是静止的，圆盘看起来以一定角度下降。当观察者从更远的外围观察刺激时，感知到的下降角度会增加。我们使用三维傅里叶分析来检查显示中的一阶和二阶信息含量，并展示如何使用我们的结果来描述真实世界情况中的感知空间/时间不连续性。
结论/意义：在边缘处圆盘方向的感知转变与一种模型一致，该模型认为中央凹处理分离了一阶和二阶运动信息，而外围处理则整合了一阶和二阶运动信息。我们认为感知到的失真可能会影响现实世界的视觉观察。为此，我们提出了一个关于棒球运动中曲线球和上升快球感知的假设和分析。曲线球是一个可测量的物理现象：球的旋转产生的力不平衡导致球偏离直线，并遵循平滑的抛物线轨迹。然而，曲线球也是一个感知难题，因为击球手经常报告说，当球接近本垒板时，球的飞行位置会发生戏剧性且几乎不连续的转变。我们认为，位置的不连续转变的感知结果来自于中央凹和外围处理之间的差异。
