Kiely Patricia M, Crewther Sheila G, Crewther David P
La Trobe University, Melbourne, Victoria, Australia.
Percept Psychophys. 2007 Aug;69(6):1035-9. doi: 10.3758/bf03193941.
Recognition of phantom objects--those with contours defined by rapid contrast reversal of adjacent fields of dark and light random dots--was investigated under conditions of abrupt or ramped onset and offset. Discrimination contrast thresholds were determined for a random-dot phantom letter in four possible orientations. For abrupt onset or offset, thresholds were almost independent of the duration of presentation time, over a range that varied tenfold, from 34-340 msec. However, when the onset and offset were shaped by a triangular envelope, thresholds were raised, so that form blindness occurred even when peak d ot contrasts exceeded 60%. Also under ramped onset and offset conditions, threshold contrast varied strictly linearly with stimulus duration in all subjects, suggesting a new construct--contrast velocity, the rate of change of contrast critical for phantom-object recognition.
对虚幻物体的识别——那些轮廓由相邻的暗点和亮点随机区域的快速对比度反转所定义的物体——在突然或斜坡式的起始和结束条件下进行了研究。确定了一个随机点虚幻字母在四个可能方向上的辨别对比度阈值。对于突然的起始或结束，在34至340毫秒的十倍变化范围内，阈值几乎与呈现时间的持续时间无关。然而，当起始和结束由三角形包络线塑造时，阈值会提高，以至于即使峰值点对比度超过60%也会出现形状盲视。同样在斜坡式起始和结束条件下，所有受试者的阈值对比度都与刺激持续时间严格呈线性变化，这表明了一种新的概念——对比度速度，即对于虚幻物体识别至关重要的对比度变化率。
