Chen Y, Bedell H E, Frishman L J, Levi D M
Department of Psychology, Harvard University, Cambridge, MA 02138, USA.
Vision Res. 1998 May;38(9):1265-72. doi: 10.1016/s0042-6989(97)00282-4.
Velocity discrimination thresholds were determined for 1 c/deg drifting gratings when uncertainty about the reference velocity was introduced by interleaving stimuli with different reference velocities from trial to trial. When drifting gratings with reference velocities spanning 4 octaves (1-16 deg/sec) were mixed randomly within a series of trials, the velocity discrimination threshold for a 4 deg/sec stimulus increased by more than a factor of 3. The threshold elevation decreased as the range of interleaved velocities was reduced from 4 to approx. 0.75 octaves, below which velocity interleaving had little effect. In contrast, when gratings that spanned a 4-octave range in spatial frequency were interleaved on successive trials, velocity discrimination for 4 deg/sec was essentially unaffected. Our results indicate that the psychophysical mechanisms underlying velocity discrimination are not spatial-frequency specific, but are turned to the velocity or speed of the stimulus.
当在逐次试验中穿插呈现具有不同参考速度的刺激，从而引入关于参考速度的不确定性时，测定了1周/度漂移光栅的速度辨别阈值。当参考速度跨越4个八度（1-16度/秒）的漂移光栅在一系列试验中随机混合时，4度/秒刺激的速度辨别阈值增加了3倍多。随着穿插速度范围从4个八度减小到约0.75个八度，阈值升高降低，低于该范围时速度穿插几乎没有影响。相反，当在连续试验中穿插呈现空间频率跨越4个八度范围的光栅时，4度/秒的速度辨别基本不受影响。我们的结果表明，速度辨别背后的心理物理机制不是空间频率特异性的，而是针对刺激的速度或速率。
