AS Level Psychology (9990) Case Studies Practice Exam 2026 – Complete Test Prep

In EEG, the frequency is about how often the brain waves repeat in a given time—how many cycles occur each second. It’s measured in hertz, and it tells us how fast the neural oscillations are varying. This is different from how tall the waves are (amplitude) or the overall voltage of the signal. So the correct idea is the number of events per fixed time. Higher frequencies mean faster oscillations, lower frequencies mean slower ones, which helps define bands like delta, theta, alpha, beta, and gamma.