vahvistusharha

Vahvistusharha, or confirmation bias in English, is a cognitive bias in which people tend to favor information that confirms their preconceptions regardless of its accuracy. It affects how people search for evidence, interpret data, and remember past events, often leading to distorted conclusions. The term is widely used in psychology, education, journalism, and public discourse to describe a systematic pattern of information processing that reinforces existing beliefs.

Manifestations include selective information seeking (preferring sources that support one’s view), biased interpretation of ambiguous evidence in a way that favors one’s stance, and memory biases that enhance recall of confirming information while forgetting disconfirming data. The bias can operate both consciously and unconsciously and interacts with other cognitive biases such as motivated reasoning and the availability heuristic.

Vahvistusharha appears across many domains, including politics, science, and everyday decision making. It can contribute to polarization, resistance to new evidence, and persistent errors in judgment, yet it is a normal feature of human cognition given finite information processing capacity.

Mitigation strategies emphasize deliberate exposure to disconfirming evidence, skepticism toward source credibility, and structured argumentative approaches such as considering alternative hypotheses, preregistered analyses, and blind assessment. Education about cognitive biases and practices that encourage curiosity and intellectual humility are also recommended.

Historically, confirmation bias was demonstrated in experiments by Peter Wason in the 1960s, and has since been studied extensively by psychologists such as Tversky and Kahneman. In Finnish literature, vahvistusharha is used to refer to this bias and is discussed in the context of critical thinking and media literacy.