Better Daylight, Sharper Decisions

Thirty knowledge workers each spent a week in two near-identical offices, one fitted with glass that let in the full daylight spectrum and one with ordinary blinds that dimmed it. Measured on their own wrists and in their own performance, the difference was marked: in the brighter, daylit week they slept around half an hour longer and scored roughly forty per cent higher on simulations of complex, higher-order decision-making. Because everyone did both conditions, each person acted as their own comparison, which makes daylight the likely cause rather than chance differences between people. It remains a small, week-long study, so it shows the effect rather than its ceiling. What it adds to the older window research is a performance outcome you can see: not just better sleep, but better judgement the next day. For a woman who leads and decides for a living, it frames daylight as an input to the quality of her thinking, and a reason to treat light at her desk as non-negotiable.