The reason the first and last items survive the list

Read a list of twelve items aloud and ask for recall. The first two and the last two come back; items five to eight are largely gone. Change nothing but insert a thirty-second unrelated task before recall and the last items disappear while the first ones remain.

What everyone sees

The curve is often explained as importance: openings and closings matter, so people pay more attention to them. That explanation predicts a single mechanism operating at both ends, which the delay experiment rules out — one end is destroyed by a short delay and the other is not.

What is actually happening

Murdock’s serial position work established the U-shape, and the two ends have distinct causes. Early items enter a rehearsal advantage and are transferred to longer-term storage, producing primacy. Late items remain in a short-lived store at the moment of recall, producing recency, which a filled delay eliminates. Glanzer and Cunitz demonstrated the dissociation directly. Middle items receive neither advantage and compete with neighbours on both sides.

Why it stays hidden

The structure hides because recall reports content without provenance. A remembered item does not arrive labelled as rehearsed or as still-in-the-buffer, so the two mechanisms are experienced identically. The single-cause explanation is available, intuitive and wrong in a way that ordinary experience cannot detect, since nobody runs the delay condition on themselves.