Gegenfurtner K R
Max-Planck-Institute für biologische Kybernetik, Tübingen, Germany.
Vision Res. 1998 Mar;38(6):881-8. doi: 10.1016/s0042-6989(97)00214-9.
Contrast thresholds for identification of the direction of motion were determined for sinusoidal gratings and plaid patterns moving in eight possible directions. Since plaid patterns are the sum of two component gratings, a prediction of the thresholds for plaids can be made by assuming that the motions of both component gratings are independently identified (probability summation). In agreement with standard two-stage models of plaid perception, our results show that for stimuli defined by luminance contrast, plaid direction thresholds can be predicted well from the component thresholds. This also holds for fast-moving isoluminant plaid patterns, but for slowly moving (< 4 Hz) isoluminant plaids, direction thresholds were substantially higher than the prediction from the components. In the latter case, subjects frequently were unable to identify the motion of the plaid in the pattern direction, even when the direction of motion of both components could be reliably identified. Different mechanisms might underlie the perception of luminance and isoluminant plaids at slow speeds.
针对在八个可能方向上移动的正弦光栅和方格图案，确定了用于识别运动方向的对比度阈值。由于方格图案是两个分量光栅的总和，通过假设两个分量光栅的运动是独立识别的（概率求和），可以对方格的阈值进行预测。与标准的方格感知两阶段模型一致，我们的结果表明，对于由亮度对比度定义的刺激，方格方向阈值可以根据分量阈值很好地预测。这对于快速移动的等亮度方格图案也成立，但对于缓慢移动（<4 Hz）的等亮度方格，方向阈值远高于根据分量得出的预测值。在后一种情况下，即使两个分量的运动方向能够可靠识别，受试者也常常无法识别方格图案方向上的运动。低速时亮度方格和等亮度方格的感知可能有不同的机制。
