H-infinity time-varying adaptive filtering of pupil diameter for affective sensing - biomed 2009.

Recently, it has been confirmed that the diameter of the human pupil, which is controlled by the Autonomic Nervous System (ANS), responds to cognitive and emotional processes. However, it is also well known that the dominant factor in determining pupil diameter (PD) is the pupillary light reflex (PLR), which decreases the pupil size as larger amounts of light are sensed by the retina. In this study, we attempt to minimize the PLR-driven PD changes in the PD signal measured during human-computer interaction, through an Adaptive Interference Canceller (AIC), with the H8 time-varying (HITV) adaptive algorithm, so that the output of the AIC, the Modified Pupil Diameter (MPD), can be used to estimate the affective changes of a computer user. The results of this study confirm that the AIC with the HITV adaptive algorithm is able to minimize the PD changes caused by PLR to an acceptable level, which will allow the monitoring of affective changes in a computer user through the resulting MPD signal.