A flaw in experimental design where the so-called "placebo" or control condition isn't truly neutral or inert, but instead contains hidden factors that skew the results. This bias invalidates comparisons because the baseline isn't a clean zero; it's already tilted. Common in psychology and medicine, it happens when researchers don't account for the placebo's own effects—like the color of a pill, a practitioner's demeanor, or the simple act of receiving any attention—which can exaggerate or mask the real treatment's impact. It's building your scientific house on a crooked foundation.
Example: A study on an herbal "mood-booster" uses a placebo pill made of plain sugar. But if participants can taste/smell the distinct herbs in the real pill, the placebo isn't blind. The Biased Placebo Bias occurs: the "control" group knows they didn't get the real thing, potentially depressing their reported mood and making the herbal pill seem more effective than it is.
by Dumu The Void February 4, 2026
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