Near-infrared spectroscopy (NIRS) is a technology that uses the absorption of near-infrared light to reveal changes in blood flow related to brain activity.

Unlike fMRI, which requires participants to remain motionless inside the scanner, NIRS involves placing a cap with light emitters and detectors on the participant’s head. This technology is particularly useful for researchers studying brain activity in infants because these young study volunteers can sit on their caregiver’s lap, with some freedom of motion while they participate in research.