Confirmation bias does not feel like bias from the inside. It feels like being right.
Most people picture bias as a conclusion reached despite the evidence. Confirmation bias is subtler: it shapes which evidence gets noticed, searched for, and remembered in the first place, tilting the whole process toward whatever belief was already in place before the looking started.
Psychologist Raymond Nickerson’s 1998 review, the field’s standard reference on the topic, opens by naming it as a leading candidate for the single most problematic feature of human reasoning. He traces the bias through three separate stages: how evidence is searched for, which evidence gets selected for attention, and how ambiguous evidence gets interpreted. Each stage independently skews toward confirming what a person already believes rather than testing it.
Nickerson does not treat the bias as a pure defect. He also considers whether it sometimes serves an adaptive function, a question the literature has continued to debate since. But the core finding holds across science, law, medicine, and everyday judgment: the mind is not a neutral evidence-processor, it is a lawyer for conclusions already reached.
Source: Nickerson, R. S. (1998). “Confirmation Bias: A Ubiquitous Phenomenon in Many Guises.” Review of General Psychology, 2(2), 175–220.