De Weerd P, Vandenbussche E, Orban G A
Laboratorium voor Neuro- en Psychofysiologie, Katholieke Universiteit te Leuven, Belgium.
Behav Brain Res. 1990 Nov 30;40(3):201-14. doi: 10.1016/0166-4328(90)90077-r.
We measured 73.5% correct just noticeable differences (JNDs) in bar orientation with the method of constant stimuli and with a Wetherill and Levitt staircase procedure, using a total of 25 cats. For the same number of trials per threshold assessment, the variability of the threshold remained independent of the testing method used. However, the JNDs measured using the method of constant stimuli were significantly influenced by the range of the orientation differences (ODs) utilized for measuring the JND. This effect was particularly large in incompletely trained cats, but it also was significant in extensively trained subjects. On the other hand, staircase threshold measurements were not affected by the starting OD, independently of how well the animals had been trained. This shows that the staircase procedure is a more efficient instrument with which to measure JNDs in orientation than is the method of constant stimuli. With the staircase procedure, we found that the JNDs measured at oblique reference orientations did not exceed those measured at principal reference orientations (no oblique effect). Two earlier studies from this laboratory using the method of constant stimuli did report an oblique effect. Our data suggest that this oblique effect might stem from a less efficient training at the right oblique reference orientation in these studies, combined with a relatively inefficient testing procedure such as the constant stimuli method.
我们使用恒定刺激法和韦瑟里尔与莱维特阶梯程序，对总共25只猫测量了条形方向上73.5%正确的恰可察觉差异（JND）。对于每次阈值评估的相同试验次数，阈值的变异性与所使用的测试方法无关。然而，使用恒定刺激法测量的JND受用于测量JND的方向差异（OD）范围的显著影响。这种效应在训练不完全的猫中尤为明显，但在训练广泛的受试者中也很显著。另一方面，阶梯阈值测量不受起始OD的影响，与动物的训练程度无关。这表明，与恒定刺激法相比，阶梯程序是一种测量方向JND更有效的工具。通过阶梯程序，我们发现，在倾斜参考方向上测量的JND不超过在主要参考方向上测量的JND（无倾斜效应）。该实验室之前两项使用恒定刺激法的研究确实报告了倾斜效应。我们的数据表明，这种倾斜效应可能源于这些研究中在右倾斜参考方向上训练效率较低，以及诸如恒定刺激法等相对低效的测试程序。
