Decimals are not processed automatically, not even as being smaller than one.

Common fractions have been found to be processed intentionally but not automatically, which led to the conclusion that they are not represented holistically in long-term memory. However, decimals are more similar to natural numbers in their form and thus might be better candidates to be holistically represented by educated adults. To test this hypothesis, we investigated the automatic processing of decimals by college students in 4 experiments. When decimals were presented in a familiar form (e.g., 0.3, 0.05) the length of the stimuli (i.e., the number of digits) dominated performance rather than the decimal value. When controlling for the number of digits and their location within the digit string, using the place-value task, decimals were not processed automatically in either a numerical comparison task or a physical comparison task. Under the same conditions, natural numbers were processed automatically. We conclude that decimals are not represented holistically. Results of mixed pairs of a decimal and a natural number suggest that, unlike common fractions, decimals are not automatically perceived as smaller than natural numbers. We conclude that decimal place-values (e.g., tenths, hundredths) are not represented well enough to be automatically activated, and we discuss possible explanations.

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