A fresh study suggests that the way a person’s pupils change while they concentrate hints at how well that mental scratchpad is working.

Working memory does more than hold stray reminders; it stitches together phone digits until they are dialed, keeps track of a spoken sentence until the meaning lands, and buffers half-finished ideas during problem-solving.

Unlike long-term memory, it works on a tight clock measured in seconds. Because the capacity is finite – typically three to seven items at once – small differences in efficiency can ripple through reading, mathematics, and decision-making.