Insect decisions are often evaluated as if behavioral variation around an apparently optimal response were measurement error, sensory failure, or imprecision. Yet natural decisions are made with incomplete and fluctuating sensory evidence, under changing reward structures and internal states, and through motor systems that can deliberately or intrinsically generate variable actions. This non-empirical behavioral theory separates decision noise by its point of entry into perception–decision–action sequences. It distinguishes sensory noise, environmental ambiguity, exploration, internal-state variability, and behavioral error, while treating ecological consequence and adaptive value as separate inferential questions. Decision variance can arise when the same external state generates different sensory samples, when different external states produce similar cues, when animals sample alternatives, when physiological or social state changes cue weighting, or when action selection departs from the current best-supported option. These sources are not interchangeable. Apparent error can therefore reflect limited evidence, context-inappropriate control, state-dependent valuation, or stochastic search rather than deficient sensory processing. Conversely, variability is not inherently beneficial: its value depends on uncertainty structure, costs of mistakes, temporal autocorrelation, and consequences for resource acquisition, predation, reproduction, and social information. The article proposes source-resolved decision noise as an analytical framework for insect behavior. The framework predicts that ecological interpretation improves when variance is decomposed before being labelled error, plasticity, exploration, or adaptation, and when laboratory choice metrics are linked cautiously to field-scale consequences.
