Case: Del Mar Light Switches

Norman's award-winning Del Mar house had neat rows of identical light switches (a horizontal row of 4, a vertical column of 6). Despite years of living there, no one could remember which switch controlled which light. The architects said "you'll get used to it." They never did.

Root problem: A 1-D row of switches on a wall cannot map naturally to the 2-D, horizontal layout of lights in the ceiling. Identical switches in a line = no natural mapping; the mapping problem worsens fast beyond two switches. (Same problem is dangerous in industry — and in one small airplane, identical adjacent switches for flaps and landing gear caused pilots to raise the wheels on the ground.)

The fix (Fig 4.5): Mount a floor plan of the room on a tilted plate; place each small switch on the plan where its light actually is → exact spatial natural mapping. The tilt makes the mapping readable and acts as an anti-affordance (discourages putting cups on it).

Larger point: Bad designs often arise from poor coordination among the professions (architect, contractor, electrician), not a single villain. The proper method is task analysis → Human-Centered Design (HCD). Yet decades later there are still no off-the-shelf components to build such a mapped switch panel — a recurring "the tools don't exist" lament.

Confidence

1.0 — detailed worked example.

Sources: ["DOET ch.4 'The Problem with Switches' p.135-140 (Fig 4.4-4.5)"]