School of Psychology, Georgia Institute of Technology, 654 Cherry Str NW, Atlanta, GA, 30332, USA.
Sci Rep. 2021 Jan 8;11(1):45. doi: 10.1038/s41598-020-79765-2.
It is often thought that the diffusion model explains all effects related to the speed-accuracy tradeoff (SAT) but this has previously been examined with only a few SAT conditions or only a few subjects. Here we collected data from 20 subjects who performed a perceptual discrimination task with five different difficulty levels and five different SAT conditions (5000 trials/subject). We found that the five SAT conditions produced robustly U-shaped curves for (i) the difference between error and correct response times (RTs), (ii) the ratio of the standard deviation and mean of the RT distributions, and (iii) the skewness of the RT distributions. Critically, the diffusion model where only drift rate varies with contrast and only boundary varies with SAT could not account for any of the three U-shaped curves. Further, allowing all parameters to vary across conditions revealed that both the SAT and difficulty manipulations resulted in substantial modulations in every model parameter, while still providing imperfect fits to the data. These findings demonstrate that the diffusion model cannot fully explain the effects of SAT and establishes three robust but challenging effects that models of SAT should account for.
人们通常认为扩散模型可以解释与速度准确性权衡（SAT）相关的所有效应，但这之前仅在少数几个 SAT 条件或仅少数几个被试中进行了检验。在这里，我们收集了 20 名被试的数据，他们完成了一个具有五个不同难度水平和五个不同 SAT 条件的感知辨别任务（每个被试 5000 次试验）。我们发现，这五个 SAT 条件产生了稳健的 U 型曲线，分别对应于：（i）错误和正确反应时间（RT）之间的差异，（ii）RT 分布标准差与均值的比值，以及（iii）RT 分布的偏度。关键的是，只有对比随漂移率变化，只有 SAT 随边界变化的扩散模型无法解释这三个 U 型曲线中的任何一个。此外，允许所有参数在条件之间变化，揭示了 SAT 和难度操纵都导致了每个模型参数的实质性调制，同时仍然对数据提供了不完美的拟合。这些发现表明，扩散模型不能完全解释 SAT 的影响，并确立了三个稳健但具有挑战性的效应，SAT 的模型应该对此加以解释。
