Sustaining student attention during lectures presents a significant pedagogical challenge, as cognitive focus typically declines after 10 to 20 minutes. Numerous variables influence attentional capacity, among which Indoor Environmental Quality (IEQ) plays a critical role. Multiple IEQ factors—including air quality, thermal comfort, lighting conditions, and acoustics—have been empirically linked to fluctuations in cognitive performance, attention levels, and mental relaxation. In educational contexts, understanding the neurocognitive implications of IEQ is essential, given the direct correlation between mental states and learning effectiveness.

This study investigates the effects of various IEQ factors, specifically air temperature (T), relative humidity (RH), and daylight exposure, on students’ attention and relaxation during lecture sessions, focusing on undergraduate design students. The investigation was conducted in a controlled experimental setting simulating a typical lecture environment. Two sessions were carried out, each comprising four scenarios:
(i) baseline condition,
(ii) enhanced daylight exposure,
(iii) increased RH, and
(iv) elevated T.

Participants wore portable, non-invasive electroencephalogram (EEG) headsets to continuously record neurophysiological activity during each lecture scenario. Concurrently, environmental data—T, RH, carbon dioxide (CO2), total volatile organic compounds (TVOC), and particulate matter (PM)—were collected via sensors, while participants’ subjective experiences were assessed using pre- and post-experiment questionnaires. A mixed-methods approach was employed to triangulate EEG measurements with self-reported cognitive states. EEG-derived indicators (attention and relaxation levels) were analyzed alongside environmental and subjective data to identify statistical correlations using Pearson coefficient (r).

Objective measures indicated that increased natural light enhanced participants’ sense of relaxation but modestly impaired attention, suggesting a trade-off between restorative effects and cognitive focus. Optimal attention was observed under moderately warm and dry conditions (T: ~25–26 °C; RH: 16–19 %), with attention positively correlated with T (r = 0.32) and negatively with RH (r = -0.50). In contrast, relaxation peaked under slightly cooler and more humid conditions (T: ~23–24 °C; RH: 24–26 %). Elevated CO2 and PM2.5 levels were associated with reduced attention (r = -0.47 and r = -0.46), while relaxation showed weaker but positive correlations with PM2.5 (r = 0.38), PM1.0 (r = 0.35), and CO2 (r = 0.32). Ultrafine particles (PM0.3, PM0.5) and TVOC showed negligible associations with cognitive outcomes.

In contrast, self-report data presented a more nuanced picture. Pre-exposure questionnaires suggested participants felt more focused in the baseline environment, yet post-exposure reports reflected increased perceived attention with greater natural light exposure. While temperature did not significantly influence self-reported attention levels, participants consistently noted its sensory impact in qualitative feedback.

These findings highlight the complexity of IEQ effects on cognition, revealing discrepancies between subjective perception and objective performance. By integrating EEG data with environmental metrics and self-reports, this study underscores the importance of multi-sensory, evidence-based design strategies to enhance cognitive function in learning environments.

Keywords: Indoor Environmental Quality, non-invasive Electroencephalogram devices, Lecture Classroom, Attention, Relaxation.