Standardized speech quality assessments should optimally occur in soundproof environments with minimal noise interference. However, poor ventilation in such environments can lead to increased CO2concentrations, which may affect cognitive function and judgement. This study investigates whether CO2levels affect speech quality ratings and response behaviour in listening tests. Across over 5,000 trials with 24 participants, we found three key effects: (1) higher CO2levels were associated with faster response times, indicating more impulsive decision-making; (2) ratings of poor-quality samples became more favorable, and high-quality samples less favorable under high CO2, suggesting reduced perceptual discrimination; (3) rating variability decreased, implying diminished sensitivity. These findings highlight a previously overlooked factor in speech quality research: ambient air quality may introduce bias into subjective ratings.

Traditional 2D video telephony systems often fail to convey critical non-verbal cues and spatial depth, limiting naturalistic remote communication and contributing to user fatigue. This study systematically investigates the experiential and interactive benefits of stereoscopic 3D video telephony compared to conventional 2D video calls. Thirty participants engaged in two communicative tasks—a free conversation and a game of Taboo—using a shutter-glasses-based stereoscopic setup and a matched 2D control. Measures included user satisfaction (UEQ), non-verbal immediacy (NIS-O), communication quality (audiovisual ratings, comfort, cognitive workload), and immersion (Film-IEQ). Results consistently demonstrated significantly higher user satisfaction, richer non-verbal communication, improved perceived audiovisual quality, and greater immersion in the 3D condition without increased cognitive workload or physical discomfort. These findings highlight the value of stereoscopic 3D video to enhance remote interpersonal interactions by providing depth cues that support more natural and engaging communication. The study contributes empirical evidence guiding the design and evaluation of emerging immersive telepresence technologies, offering a benchmark for future volumetric and point-cloud-based 3D communication systems.

The ability to establish eye contact is a central aspect of human communication and interaction. In video communication, however, it is impaired by the physical separation between camera and screen. This study investigates the effects of three video telephony configurations – standard video calls, teleprompter-assisted calls, and AI-based gaze correction – on user experience and perceived communication quality. In a collaborative task with 32 participants, we evaluated subjective dimensions such as Engagement, Naturalness of Eye Contact, and Social Presence across four conditions, including a face-to-face baseline. The results indicate that face-to-face interactions significantly outperform all video conditions in central dimensions. Notably, technical attempts to replicate natural eye contact, particularly through AI-based gaze correction, proved ineffective, leading to reduced perceived Naturalness of Eye Contact and increased Anxiety. These findings point to a heightened user sensitivity to artificial modifications in socially salient contexts. Although teleprompter-based solutions elicited less Anxiety, their technical constraints limit practical applicability. We conclude that current implementations of AI gaze correction, specifically the version in our study, are not yet suitable for enhancing conversational quality. Future efforts might benefit from focusing on design that build on the unique affordances of digital interaction, rather than aiming to replicate face-to-face dynamics.

Objectively measuring affective states remains a recurring challenge in psychology and user experience research. A promising proxy for perceived arousal is the momentary assessment of the pupil diameter. However, the pupillometric signal is highly susceptible to variations in stimulus luminance, which can substantially confound the results. We introduce a method to improve the accuracy of pupillometric signals as an arousal predictor by eliminating frame-by-frame luminance variations in visual stimuli (i.e. scaling the brightness value for all pixels such that each frame has the same average luminance). This process was termed "equalization". We tested our approach in a study with 31 participants between the ages of 21 and 64. Our study focused on two metrics: (1) the perceived quality of the stimuli should not be affected by the process, and (2) the predictive power of the pupillometric signal for the perceived arousal should be greater for the equalized videos than for the non-equalized ones. We used a within-subjects design, where each participant rated their affective response and five distinct quality dimensions of four videos (two in the equalized and two in the non-equalized condition). Our results indicate that the equalization process does improve the predictive power of the pupillometric signal by a substantial amount. Statistical analyses also show that the participants rated all quality dimensions equivalently for an equalized and non-equalized variant of the same stimulus, with only small differences that are limited to a subset of the perceptual dimensions. While potentially limiting the efficacy of the process in some scenarios, the strengthened explanatory power of the pupillometric signal leaves room for a wide range of possible applications.