Comparison of two pupillometric measures as indicators of cognitive strain and under the influence of screen luminance.

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.

A meta-analytic review of the reliability of the Index of Cognitive Activity concerning task-evoked cognitive workload and light influences.

The Index of Cognitive Activity (ICA) was introduced as a promising pupillary workload measure for field investigations since, unlike pupil dilation, it is not affected by illumination. Recent studies have investigated the ICA for task-evoked cognitive workload with contradictory findings. However, few studies investigated the influence of illumination on the ICA. Therefore, to examine inconsistencies regarding the reliability for workload measurement and the effects of light, a meta-analysis was conducted based on a structured literature review. The meta-analysis considered k = 14 studies with a total sample size of N = 751 participants. Results showed significant effects for workload (r = 0.61) and light (r = 0.45) on the ICA. Since moderating effects were found for several between-study differences, it seems likely that different cognitive processes and settings affect the indicator and should be considered in empirical investigations. According to the findings, the ICA is a reliable indicator for task-evoked workload. However, light influences were found which indicates that evidence-based conclusions regarding the ICA's practical applicability require further research.

The Index of Cognitive Activity - Eligibility for task-evoked informational strain and robustness towards visual influences.

Various researchers have proposed pupillometric indicators to assess a person's cognitive strain. However, to distinguish the variation of pupil light response from psychosensory pupil response in experimental field conditions is a challenge. The Index of Cognitive Activity (ICA) addresses this problem by wavelet separation. This research investigates the ICA's sensitivity for multiple level task-evoked cognitive activity and visual influences concerning informational work tasks. Objective and subjective measures assessed cognitive strain of participants (N = 22) during various tasks. In a first experiment, mental arithmetic tasks were used to induce different levels of cognitive activity. In a second experiment, influences of screen polarity and presentation of information were investigated (N = 18). The results indicate that eye metrics are rarely sensitive to slight variations in task difficulty. Moreover, the ICA is likely to be sensitive towards constant screen illumination and shows tendencies regarding changes in displayed information. Possible ramifications for the objective assessment of cognitive strain are discussed.