Working memory is the cognitive function most directly responsible for how intelligent you seem — and how intelligent you feel. Understanding its biological capacity limit (4 ± 1 chunks), why the prefrontal cortex is uniquely vulnerable to stress and sleep deprivation, and the specific interventions with RCT evidence for improvement is the difference between vague advice and a precision protocol. This guide covers the neuroscience, the clinical evidence, and the four-layer optimisation protocol that Peter has refined across 40+ Creyos testing sessions.