A primary objective of optical see-through (OST) Augmented Reality (AR) systems is to enable users to perceive the depth of AR objects with the same accuracy as they perceive the depth of realworld objects. Previous studies have shown that individuals often make depth judgments that either underestimate or overestimate the depth of AR objects compared to real-world objects. Recently, OST AR devices have incorporated eye-tracking technology, offering the opportunity to objectively measure and investigate the depth-dependent components of the human visual system (e.g., eye vergence angle) while perceiving the depth of real and AR objects. This paper measures and examines the eye vergence angle (EVA) for both real and AR objects at four different depths (0.35 m, 0.75 m, 1.5 m, and 4.0 m) using integrated eye-tracking systems of the two commercial devices: Microsoft HoloLens 2 and Magic Leap 2. The experiment considered a four-alternative forced-choice visual discrimination task with a repeated-measures design, involving 24 participants. Our findings showed that subjective (verbal estimation) and objective (EVA) measures of depth perception were consistent with the depth of both real and AR objects in both OST AR devices. The results demonstrated individual differences in EVA for each device across various depths. No difference in EVA was identified between real and AR objects. Additionally, the EVA range differs between the OST AR devices for each depth. These findings indicate that objective EVA measurements can not be generalized across different OST AR devices and individuals.

Virtual Reality (VR) technology has advanced to include eye-tracking, allowing novel research, such as investigating how our visual system coordinates eye movements with changes in perceptual depth. The purpose of this study was to examine whether eye tracking could track perceptual depth changes during a visual discrimination task. We derived two depth-dependent variables from eye tracker data: eye vergence angle (EVA) and interpupillary distance (IPD). As hypothesized, our results revealed that shifting gaze from near-to-far depth significantly decreased EVA and increased IPD, while the opposite pattern was observed while shifting from far-to-near. Importantly, the amount of change in these variables tracked closely with relative changes in perceptual depth, and supported the hypothesis that eye tracker data may be used to infer real-time changes in perceptual depth in VR. Our method could be used as a new tool to adaptively render information based on depth and improve the VR user experience.

Neurochemical systems are well studied in animal learning; however, ethical issues limit methodologies to explore these systems in humans. Pupillometry provides a glimpse into the brain's neurochemical systems, where pupil dynamics in monkeys have been linked with locus coeruleus (LC) activity, which releases norepinephrine (NE) throughout the brain. The objective of my research is to understand the role of neurochemicals in human learning. Specifically, I aim to 1) Establish a non-invasive method to study the role of neurochemicals in human learning, 2) Develop methods to monitor learning in real time using pupillometry, and 3) Discover causal relationships between neurochemicals and learning in human subjects. In this article, to address Objective 1, we present evidence that pupil dynamics can be used as a surrogate measure of neurochemical activity during learning. Specifically, we hypothesize that norepinephrine modulates the encoding of memories, the influence of which can be measured with pupil dynamics. To examine this hypothesis a task-irrelevant learning paradigm was used, in which learning is boosted for stimuli temporally paired with task targets. We show that participants better recognize images that are paired with task targets than distractors and, in correspondence, that pupil size changes more for target-paired than distractor-paired images. To further investigate the hypothesis that NE nonspecifically guides learning for stimuli that are present with its release, a second procedure was used that employed an unexpected sound to activate the LC--NE system and induce pupil-size changes; results indicated a corresponding increase in memorization of images paired with the unexpected sounds. Together, these results suggest a relationship between the LC--NE system, pupil-size changes, and learning. My ongoing work aims to develop methods to monitor learning in real time by investigating the relationship between, pupil size changes, eye movement and learning in context of a free visual search task. Future work will investigate the causal relationship between neurochemicals, learning and pupil dynamics by using NE specific drugs to up- and down-regulate levels of NE during learning.