Devkar Deepna, Wright Anthony A, Ma Wei Ji
Department of Neurobiology & Anatomy, University of Texas Medical School, Houston, TX, USA.
Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA.
J Vis. 2017 Sep 1;17(11):4. doi: 10.1167/17.11.4.
Since sensory measurements are noisy, an observer is rarely certain about the identity of a stimulus. In visual perception tasks, observers generally take their uncertainty about a stimulus into account when doing so helps task performance. Whether the same holds in visual working memory tasks is largely unknown. Ten human and two monkey subjects localized a single change in orientation between a sample display containing three ellipses and a test display containing two ellipses. To manipulate uncertainty, we varied the reliability of orientation information by making each ellipse more or less elongated (two levels); reliability was independent across the stimuli. In both species, a variable-precision encoding model equipped with an "uncertainty-indifferent" decision rule, which uses only the noisy memories, fitted the data poorly. In both species, a much better fit was provided by a model in which the observer also takes the levels of reliability-driven uncertainty associated with the memories into account. In particular, a measured change in a low-reliability stimulus was given lower weight than the same change in a high-reliability stimulus. We did not find strong evidence that observers took reliability-independent variations in uncertainty into account. Our results illustrate the importance of studying the decision stage in comparison tasks and provide further evidence for evolutionary continuity of working memory systems between monkeys and humans.
由于感官测量存在噪声，观察者很少能确定刺激的身份。在视觉感知任务中，当考虑刺激的不确定性有助于任务表现时，观察者通常会将其纳入考量。在视觉工作记忆任务中是否也是如此，在很大程度上尚不清楚。十名人类受试者和两只猴子受试者在一个包含三个椭圆的样本显示和一个包含两个椭圆的测试显示之间定位了方向上的单一变化。为了操纵不确定性，我们通过使每个椭圆或多或少地拉长（两个级别）来改变方向信息的可靠性；可靠性在不同刺激之间是独立的。在这两个物种中，一个配备“不确定性无差异”决策规则的可变精度编码模型，该模型仅使用有噪声的记忆，对数据的拟合效果很差。在这两个物种中，一个观察者还会考虑与记忆相关的可靠性驱动的不确定性水平的模型提供了更好的拟合。特别是，低可靠性刺激中的测量变化比高可靠性刺激中的相同变化权重更低。我们没有发现有力证据表明观察者考虑了与可靠性无关的不确定性变化。我们的结果说明了在比较任务中研究决策阶段的重要性，并为猴子和人类之间工作记忆系统的进化连续性提供了进一步的证据。
