unexpectedness

Unexpectedness is the quality of a phenomenon that is not anticipated within a given context. It arises when outcomes differ from an individual's expectations or the established pattern of events, and it intersects with notions of novelty, surprise, and incongruity. The term is used across psychology, information theory, and the arts.

In cognitive science, expectation is shaped by prior knowledge and cues; when new information conflicts with these expectations, a prediction error occurs. Surprisal, a formal measure from information theory, assigns higher values to unlikely events via I(p) = -log2 p. Bayesian approaches treat unexpected events as powerful drivers of belief revision, quantified as Bayesian surprise.

Neural and behavioral research links unexpectedness to attentional capture and learning signals, including dopaminergic responses to surprising outcomes. In aesthetics and humor, unexpectedness often arises from incongruity or misdirection, contributing to engagement but potentially impairing comprehension if excessive.

Practically, designers and communicators modulate unexpectedness to guide attention, teach, or entertain, while in risk communication or safety-critical domains, too much surprise can be disorienting. Distinctions are sometimes drawn between unexpectedness (deviation from expectation) and novelty (newness).

See also: surprise, novelty, anomaly, incongruity, information theory, prediction error.