The pupil diameter has been shown to provide insight to a person's experienced cognitive strain. Pupillary light responses, however, make this measure unreliable in uncontrolled settings. Two derived indicators—Index of Cognitive Activity (ICA) and Index of Pupillary Activity (IPA)—aim to ‘eliminate’ lighting influences, changing based only on the perceived cognitive strain. The IPA potentially offers a valuable alternative to the ICA through its fully transparent calculation, which lifts the restrictions to proprietary software and supported eye trackers. The measures are examined and compared based on two experimental studies; (i) as indicators of cognitive strain during mental arithmetic tasks and (ii) under different conditions of computer screen luminance. Results indicate that neither indicator differentiates between the increasing levels of cognitive strain. Differences in screen luminance are reflected in both indicators, although differently between the conditions. Both results contradict the claims of the indicators and further investigations are thus required.

中文翻译：

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两种瞳孔测量作为认知紧张指标和屏幕亮度影响下的比较

瞳孔直径已被证明可以洞察一个人所经历的认知压力。然而，瞳孔光反应使得该测量在不受控制的环境中不可靠。两个衍生指标——认知活动指数（ICA）和瞳孔活动指数（IPA）——旨在“消除”照明影响，仅根据感知到的认知紧张而变化。IPA 通过其完全透明的计算，有可能为 ICA 提供有价值的替代方案，从而解除了对专有软件和支持的眼动仪的限制。根据两项实验研究对这些措施进行检查和比较；（i）作为心算任务期间认知紧张的指标，以及（ii）在不同的计算机屏幕亮度条件下。结果表明，这两个指标都无法区分认知紧张程度的增加。屏幕亮度的差异反映在两个指标中，尽管条件之间有所不同。这两项结果都与指标的说法相矛盾，因此需要进一步调查。