Abstract

The Operational Momentum (OM) is the systematic tendency to overestimate the answers to addition problems and underestimate the answers to subtraction problems. This effect has been found both in adults and infants using non-symbolic numerical quantities, and it is thought to arise from interactions between the spatial and numerical systems, as a side effect of attentional updating along the mental number line - attention is shifted to the right (larger numbers) for addition and to the left (smaller numbers) for subtraction. This experiment was aimed at investigating whether the OM effect is present even for the representation of increasing ordinal relations among continuous quantities in 12-month-olds. After been habituated to increasing sizebased sequences, infants showed a preference for an increasing against-momentum sequence vs. an increasing with-momentum sequence. Results are in line with the hypothesis that continuous and discrete quantities share a common representational system.