Kamienkowski Juan Esteban, Sigman Mariano
Integrative Neuroscience Laboratory, Physics Department, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
PLoS One. 2008 Sep 12;3(9):e3196. doi: 10.1371/journal.pone.0003196.
When two tasks are presented within a short interval, a delay in the execution of the second task has been systematically observed. Psychological theorizing has argued that while sensory and motor operations can proceed in parallel, the coordination between these modules establishes a processing bottleneck. This model predicts that the timing but not the characteristics (duration, precision, variability...) of each processing stage are affected by interference. Thus, a critical test to this hypothesis is to explore whether the quality of the decision is unaffected by a concurrent task.
METHODOLOGY/PRINCIPAL FINDINGS: In number comparison--as in most decision comparison tasks with a scalar measure of the evidence--the extent to which two stimuli can be discriminated is determined by their ratio, referred as the Weber fraction. We investigated performance in a rapid succession of two non-symbolic comparison tasks (number comparison and tone discrimination) in which error rates in both tasks could be manipulated parametrically from chance to almost perfect. We observed that dual-task interference has a massive effect on RT but does not affect the error rates, or the distribution of errors as a function of the evidence.
CONCLUSIONS/SIGNIFICANCE: Our results imply that while the decision process itself is delayed during multiple task execution, its workings are unaffected by task interference, providing strong evidence in favor of a sequential model of task execution.
当在短时间间隔内呈现两项任务时，已系统观察到第二项任务执行的延迟。心理学理论认为，虽然感觉和运动操作可以并行进行，但这些模块之间的协调会形成一个处理瓶颈。该模型预测，每个处理阶段的时间安排而非特征（持续时间、精度、变异性……）会受到干扰的影响。因此，对这一假设的关键测试是探究决策质量是否不受并发任务的影响。
方法/主要发现：在数字比较中——与大多数具有证据标量测量的决策比较任务一样——两个刺激能够被区分的程度由它们的比率决定，称为韦伯分数。我们研究了在快速连续进行的两项非符号比较任务（数字比较和音调辨别）中的表现，其中两项任务的错误率都可以从随机水平参数化地操纵到几乎完美。我们观察到，双任务干扰对反应时间有巨大影响，但不影响错误率，也不影响作为证据函数的错误分布。
结论/意义：我们的结果表明，虽然在多任务执行期间决策过程本身会延迟，但其运作不受任务干扰的影响，这为支持任务执行的顺序模型提供了有力证据。
