THE PRECISION OF SIZE CONSTANCY
THE PRECISION OF SIZE CONSTANCY
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DOI：
10.1016/0042-6989(92)90201-s
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发表时间：
1992-08-01
期刊：
影响因子：
1.8
通讯作者：
WELCH, L
中科院分区：
文献类型：
--
作者：
MCKEE, SP;WELCH, L
目标的大小判断的精度，当目标视差随机变化，从审判到审判，进行了比较，在相同条件下的角度大小的判断精度。受试者判断一对水平线之间垂直距离的增量变化。对于客观的判断（厘米），对向的目标分离的角度随着深度的增加而减少，符合自然的物理对象的几何形状。对于角度判断（以arc min为单位），角度间隔不随视差而变化。对于对向角< 10弧分的分离，客观阈值远高于角度阈值，表明尺寸恒定性在小尺度下不起作用。在更大的尺度（> 20弧分），角度和客观阈值的韦伯分数几乎相等（约6%）的三个科目中的两个。这两个同样的主题也学会了判断“客观的大小”时，角度对向系统地增加与增加深度在一个确切的反转的自然关系。虽然他们的“反恒常性”判断不如他们的恒常性判断准确（约9%），但受试者几乎不需要练习就能学会这项任务的事实表明，恒常性本身可能是一种习得性反应。仅在固定平面中呈现的目标的角度阈值显著低于视差随机变化测量的角度阈值，表明具有正常立体视觉的观察者不能直接获得关于视网膜所对的角度的信息。
The precision of objective size judgments, made when target disparity changed at random from trial-to-trial, was compared to the precision of angular size judgments made under the same condition. Subjects judged incremental changes in the vertical distance separating a pair of horizontal lines. For the objective judgments (in cm), the angle subtended by the target separation decreased with increasing depth consistent with the natural geometry of physical objects. For the angular judgments (in arc min), the angular separation did not change with disparity. For separations subtending an angle < 10 arc min, objective thresholds were considerably higher than angular thresholds, indicating that size constancy does not function well at small scales. At larger scales (> 20 arc min), the Weber fractions for angular and objective thresholds were nearly equal (approximately 6%) for two of the three subjects. These same two subjects also learned to judge "objective size" when angular subtense systematically increased with increasing depth in an exact inversion of the natural relationship. Although their "anti-constancy" judgments were less precise (approximately 9%) than their constancy judgments, the fact that subjects could learn this task with little practice suggests that constancy itself may be a learned response. Angular thresholds for targets presented only in the fixation plane were significantly lower than the angular thresholds measured with random changes in disparity, showing that observers with normal stereopsis do not have direct access to information about the angle subtended at the retina.