Meador Kimford J, Boyd Alan, Loring David W
*Department of Neurology & Neurological Sciences, Stanford University, Stanford, California †CNS Vital Signs LLC, Morrisville, North Carolina ‡Department of Neurology, Emory University, Atlanta, Georgia.
Cogn Behav Neurol. 2017 Jun;30(2):57-61. doi: 10.1097/WNN.0000000000000121.
Initiation of response in a simple reaction time (RT) task may precede conscious perception of the stimulus. Since volitionally delayed responses may require conscious perception of the stimulus before response initiation, it has been hypothesized that volitionally delayed responses will markedly delay RT.
We conducted two experiments with separate groups of healthy volunteers (n=16; n=13) who performed computerized simple and choice RT tasks. In the standard condition, we instructed the participants to respond to a visual stimulus by pushing a button as quickly as possible. In the second condition, we instructed the participants to respond after a slight volitional delay. The second experiment had an additional volitional delay condition in which we asked participants to delay their responses by an estimated 50% above their usual standard response.
We found marked delays and increased variability when participants volitionally delayed their responses, averaging 322 ms for standard and 861 ms for delayed simple RTs (267% increase), and 650 ms for standard and 1018 ms for delayed choice RTs (157% increase). Effects did not differ across age, sex, or handedness. However, a minority of participants did not meaningfully delay their RT during the volitional delay conditions.
On average, participants had marked delays when they tried to delay their responses slightly, but a subset of participants exhibited essentially no delay despite trying to delay. We suggest some potential mechanisms that future investigations might delineate.
在简单反应时（RT）任务中，反应的启动可能先于对刺激的有意识感知。由于自主延迟反应可能需要在反应启动前对刺激有有意识的感知，因此有人推测自主延迟反应会显著延长反应时。
我们对两组健康志愿者（n = 16；n = 13）进行了两项实验，他们分别执行计算机化的简单和选择反应时任务。在标准条件下，我们指示参与者尽快按下按钮对视觉刺激做出反应。在第二种条件下，我们指示参与者在稍有自主延迟后做出反应。第二个实验还有一个额外的自主延迟条件，我们要求参与者将反应延迟至比其通常的标准反应长约50%。
我们发现，当参与者自主延迟反应时，反应时显著延长且变异性增加，简单反应时的标准平均反应时为322毫秒，延迟反应时为861毫秒（增加267%），选择反应时的标准平均反应时为650毫秒，延迟反应时为1018毫秒（增加157%）。这些效应在年龄、性别或利手方面没有差异。然而，少数参与者在自主延迟条件下并没有显著延迟其反应时。
平均而言，参与者在试图稍有延迟反应时反应时显著延长，但有一部分参与者尽管试图延迟，却基本没有延迟。我们提出了一些未来研究可能会阐明的潜在机制。
