One digit too many: brain rhythms and autonomic responses at the limits of working memory capacity

Exceeding an individual’s digit span by one digit in a 123-participant adaptive task reduces full-sequence recall from 74.1% to 51.5% and raises mental demand.

• Why it matters: It remains unclear whether physiological signals can pinpoint when working-memory demands surpass a person’s capacity rather than merely tracking load.
• What they did: Participants completed an adaptive digit span task while recording EEG, pupillometry, and photoplethysmography; overload was defined as span+1 sequences relative to each person’s calibrated span.
• The result: Pulse wave amplitude and frontal midline theta shifted with overload and serial position, but no shared physiological breakpoint emerged, suggesting capacity limits can be crossed without immediate resource exhaustion or disengagement.

AI summary of the abstract · may contain errors · not medical advice · read the paper.