The reason engagement and satisfaction diverge
Behaviour is easy to log and preference is not. A system optimised on the first will find items that produce action without producing approval.
Filed by The Archivist 2 min read
Intuition test — answer before you read on
Why can a recommender improve on every tracked metric while users report worse results?
Correct answer: B
Option A dismisses the subjective measure, but evidence indicates subjective and behavioural measures capture different, non-redundant information. Behaviour is consistent with multiple preference structures, so a system trained on it cannot separate satisfaction from capture.
A recommendation system improves on every measure it tracks while users report that the results are worse. Both observations can be accurate. Clicks and dwell time are recorded automatically; whether the item was wanted has to be asked, and what is asked is a fraction of what is logged.
What everyone sees
The divergence is read as a values problem — platforms choosing profit over experience. Incentives contribute. But the same gap appears in systems with no commercial motive, which indicates a measurement problem underneath: the available signal is a poor proxy for the objective, and optimisation exploits every gap between them.
What is actually happening
Kleinberg, Mullainathan and Raghavan formalise the difficulty of inferring what users want from what they do, showing that behavioural traces are consistent with multiple underlying preference structures, so a system trained on behaviour cannot distinguish a satisfied user from a captured one. Ekstrand and Willemsen argued that purely behavioural evaluation is insufficient for recommender research and that subjective measures capture distinct and non-redundant information. Together they describe an ordinary optimisation outcome: the objective and its proxy diverge under pressure, and the system moves toward whichever items maximise the proxy.
Why it stays hidden
The gap hides in the reporting cycle. Behavioural metrics arrive continuously, in volume, and are trusted; satisfaction is sampled occasionally, in small numbers, with wide intervals, and is discounted as noisy. The stronger evidence is therefore the weaker measure, and when the two disagree the decision goes to the one with more decimal places.
Behaviour is logged and preference is asked. Optimisation moves toward whichever one is being measured.
Behaviour is logged and preference is asked. Optimisation moves toward whichever one is being measured.
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Behaviour is logged and preference is asked. Optimisation moves toward whichever one is being measured.
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Sources & further reading 2
- Kleinberg, Mullainathan & Raghavan — the challenge of understanding what users want
- Ekstrand & Willemsen — behaviorism is not enough
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