PsychologyJuly 13, 2026

surprisal

/sərˈpraɪzəl/

Definition

A mathematical or technical measure of information content or the degree of 'unexpectedness' associated with a sensory outcome or event.

Etymology

Derived from the verb 'surprise,' which traces back to the Old French 'surprendre' (to overtake or capture). The '-al' suffix is added in information theory to turn the noun into a technical term representing the quantifiable degree of unexpectedness.

In the news

In the article, 'surprisal' refers to the cognitive tension experienced when the brain encounters information that contradicts its internal predictions. This mismatch forces the brain to expend energy to either update its worldview or alter its behavior.

Modern Neuroscience Is Starting to Look Surprisingly Similar to Freud’s Theory of the Mind

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