Double descent appears even in ordinary linear regression, tutorial paper shows

RylanSchaeffer · x · 2026-10-20

'Double Descent Demystified' began as a Stanford AI Alignment tutorial aiming to explain double descent with nothing beyond introductory linear algebra, isolating the three factors necessary to produce it. The attached figure shows three real datasets (California Housing, Diabetes, WHO Life Expectancy) plus one synthetic set all exhibit double descent in plain linear regression, with test loss spiking at the interpolation threshold. Meta-lesson: simplifying systems to their most basic pieces is tremendously valuable for identifying what really matters.

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