Evidence for Your learning environment #

Every substantive claim on the Your learning environment page is checked against current research. Here is each claim, how well today’s evidence supports it, and the sources. The full, de-duplicated source list lives on the references page.

Supported · moderate evidence — The mere presence of one’s own smartphone within reach reduces available cognitive capacity (attention and working memory) even when the phone is silent and not used.

Ward et al. (2017) found a graded ‘brain drain’ effect: performance on working-memory and fluid-intelligence tasks was best when the phone was in another room, worse on the desk, with the effect strongest for high phone-dependent users. The headline finding is well known and the direction is widely accepted, though some later replications report smaller or null effects, so strength is moderate rather than strong.

Sources: Ward, A. F., Duke, K., Gneezy, A., & Bos, M. W. (2017), Brain drain: The mere presence of one’s own smartphone reduces available cognitive capacity. Journal of the Association for Consumer Research — https://doi.org/10.1086/691462 · full reference ›

Supported · moderate evidence — People who engage heavily in media multitasking tend to show poorer sustained attention and greater susceptibility to distraction.

Uncapher & Wagner’s (2018) review concludes that heavier media multitaskers, on average, perform worse on tasks requiring sustained attention and working memory, while noting the literature is correlational and mixed in places. The association is real and replicated in aggregate but causal direction is not established, so the page frames it as a habit/correlate rather than proven cause.

Sources: Uncapher, M. R., & Wagner, A. D. (2018), Minds and brains of media multitaskers: Current findings and future directions. PNAS — https://doi.org/10.1073/pnas.1611612115 · full reference ›

Supported · strong evidence — Switching between tasks carries a time and accuracy cost, so each interruption during study requires extra effort to refocus.

Task-switching costs are one of the most robust findings in cognitive psychology: Rubinstein, Meyer & Evans (2001) and a large subsequent literature consistently show slower and more error-prone performance when alternating between tasks versus repeating one. This remains uncontested in 2026.

Sources: Rubinstein, J. S., Meyer, D. E., & Evans, J. E. (2001), Executive control of cognitive processes in task switching. Journal of Experimental Psychology: Human Perception and Performance — https://doi.org/10.1037/0096-1523.27.4.763 · full reference ›

Supported · moderate evidence — Elevated indoor carbon dioxide concentrations, of the kind that build up in crowded poorly ventilated rooms, can impair cognitive performance such as decision-making.

Allen et al. (2016, the Harvard COGfx study) found substantially lower cognitive-function scores at higher indoor CO2 and VOC levels and better ventilation conditions. The broad direction (poor ventilation / high CO2 impairs cognition) is well supported, though some controlled-exposure replications find weaker or inconsistent effects at moderate CO2 alone, so the page avoids precise thresholds and dramatic timelines.

Sources: Allen, J. G., MacNaughton, P., Satish, U., Santanam, S., Vallarino, J., & Spengler, J. D. (2016), Associations of cognitive function scores with carbon dioxide, ventilation, and volatile organic compound exposures in office workers. Environmental Health Perspectives — https://doi.org/10.1289/ehp.1510037 · full reference ›

Supported · moderate evidence — Thermal comfort affects task performance, with hot or uncomfortable indoor conditions tending to reduce concentration and output relative to a moderate, comfortable temperature.

Lan, Wargocki & Lian (2011) and related indoor-environment research show that thermal discomfort, especially warm conditions, reduces performance and increases the mental effort needed to maintain it. The relationship is real but moderate and individually variable, which is why the page recommends ‘comfortable’ rather than a single optimal degree.

Sources: Lan, L., Wargocki, P., & Lian, Z. (2011), Quantitative measurement of productivity loss due to thermal discomfort. Energy and Buildings — https://doi.org/10.1016/j.enbuild.2011.01.011 · full reference ›

Supported · moderate evidence — Background sound containing intelligible speech or lyrics interferes with reading and verbal tasks more than steady non-speech sound, because words compete with the words being processed.

The irrelevant-speech effect is well established: changing-state and meaningful auditory material (including lyrics and overheard speech) disrupts serial recall and reading more than steady sound. Perham & Vizard (2011) show music with lyrics impairing serial recall; effects vary with task and listener, supporting the page’s ‘individual’ framing.

Sources: Perham, N., & Vizard, J. (2011), Can preference for background music mediate the irrelevant sound effect? Applied Cognitive Psychology — https://doi.org/10.1002/acp.1731 · full reference ›