Gajewski Daniel A, Wallin Courtney P, Philbeck John W
Department of Psychology, The George Washington University, 2125 G Street, NW, Washington, DC, 20052, USA,
Atten Percept Psychophys. 2014 Aug;76(6):1739-51. doi: 10.3758/s13414-014-0700-9.
The angular declination of a target with respect to eye level is known to be an important cue to egocentric distance when objects are viewed or can be assumed to be resting on the ground. When targets are fixated, angular declination and the direction of the gaze with respect to eye level have the same objective value. However, any situation that limits the time available to shift gaze could leave to-be-localized objects outside the fovea, and, in these cases, the objective values would differ. Nevertheless, angular declination and gaze declination are often conflated, and the role for retinal eccentricity in egocentric distance judgments is unknown. We report two experiments demonstrating that gaze declination is sufficient to support judgments of distance, even when extraretinal signals are all that are provided by the stimulus and task environment. Additional experiments showed no accuracy costs for extrafoveally viewed targets and no systematic impact of foveal or peripheral biases, although a drop in precision was observed for the most retinally eccentric targets. The results demonstrate the remarkable utility of target direction, relative to eye level, for judging distance (signaled by angular declination and/or gaze declination) and are consonant with the idea that detection of the target is sufficient to capitalize on the angular declination of floor-level targets (regardless of the direction of gaze).
当观察物体或假定物体放置在地面上时，目标相对于眼睛水平高度的角偏角是自我中心距离的一个重要线索。当注视目标时，角偏角和相对于眼睛水平高度的注视方向具有相同的客观值。然而，任何限制转移注视时间的情况都可能使待定位物体位于中央凹之外，在这些情况下，客观值会有所不同。尽管如此，角偏角和注视偏角常常被混淆，而且视网膜离心率在自我中心距离判断中的作用尚不清楚。我们报告了两项实验，结果表明即使刺激和任务环境仅提供视网膜外信号，注视偏角也足以支持距离判断。额外的实验表明，对于中央凹外注视的目标，准确性没有损失，并且没有发现中央凹或周边偏差的系统性影响，尽管对于视网膜离心率最大的目标，精度有所下降。结果表明，相对于眼睛水平高度的目标方向在判断距离（由角偏角和/或注视偏角表示）方面具有显著作用，这与以下观点一致，即检测到目标就足以利用地面目标的角偏角（无论注视方向如何）。
