Gurnsey Rick, Roddy Gabrielle, Chanab Waël
Department of Psychology, Concordia University, Montreal, Quebec, Canada.
J Vis. 2011 Jun 17;11(7):15. doi: 10.1167/11.7.15.
Crowding is a form of lateral interaction in which flanking items interfere with the detection or discrimination of a target stimulus. It is believed that crowding is a property of peripheral vision only and that no crowding occurs at fixation. If these two claims are true, then there must be a change in the nature of crowding interactions across the visual field. In three different tasks, we determined target size and flanker separation at threshold for eccentricities of 0 to 16° in the lower visual field for 7 relative separations (1.25 to 8 times target size). In all three tasks, the magnitude of crowding increases with eccentricity; there was no crowding at fixation and extreme crowding at 16°. Using a novel double-scaling procedure, we show that the non-foveal data in all three tasks can be characterized as shifted versions of the same psychometric function such that different sections of the function characterize data at each eccentricity. This pattern of results can be understood in terms of size-dependent responses to the target and distance-dependent interference from the flankers. The data suggest that the distance-dependent interference increases with eccentricity.
拥挤是一种侧向相互作用形式，其中侧翼项目会干扰目标刺激的检测或辨别。人们认为拥挤仅是周边视觉的一种特性，在注视点不会发生拥挤。如果这两个说法属实，那么在整个视野中，拥挤相互作用的性质必然会发生变化。在三项不同任务中，我们针对下视野中0至16°的偏心度，在7种相对间距（目标大小的1.25至8倍）下确定了阈值时的目标大小和侧翼间距。在所有三项任务中，拥挤程度均随偏心度增加；在注视点没有拥挤，而在16°时出现极度拥挤。使用一种新颖的双标度程序，我们表明所有三项任务中的非中央凹数据都可被表征为同一心理测量函数的移位版本，这样该函数的不同部分就表征了每个偏心度下的数据。这种结果模式可以根据对目标的大小依赖性反应以及侧翼的距离依赖性干扰来理解。数据表明，距离依赖性干扰随偏心度增加。
