Study Description

A cognitive neuroscientist carried out a study to investigate whether evening exposure to blue-wavelength light from digital screens affects next-day cognitive function.

• Warm lighting condition: Participants read a printed paperback book under warm, non-blue-emitting ambient lighting (2700 K) for 60 minutes immediately prior to sleeping.
• Blue-light screen condition: Participants read on a tablet screen emitting high-intensity blue-wavelength light (450 nm) for 60 minutes immediately prior to sleeping.

Participants were randomly allocated to take part in only one of the conditions. The following morning, the researcher measured each participant's cognitive processing speed using a standardised visual reaction time task (with results recorded in milliseconds).