Heuristics and biases in the mental manipulation of magnitudes: Evidence from length and time production

Giovanna Mioni, Martin H. Fischer, Samuel Shaki

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


There is a debate about whether and why we overestimate addition and underestimate subtraction results (Operational Momentum or OM effect). Spatial-attentional accounts of OM compete with a model which postulates that OM reflects a weighted combination of multiple arithmetic heuristics and biases (AHAB). This study addressed this debate with the theoretically diagnostic distinction between zero problems (e.g., 3 + 0, 3 − 0) and non-zero problems (e.g., 2 + 1, 4 − 1) because AHAB, in contrast to all other accounts, uniquely predicts reverse OM for the latter problem type. In two tests (line-length production and time production), participants indeed produced shorter lines and under-estimated time intervals in non-zero additions compared with subtractions. This predicted interaction between operation and problem type extends OM to non-spatial magnitudes and highlights the strength of AHAB regarding different problem types and modalities during the mental manipulation of magnitudes. They also suggest that OM reflects methodological details, whereas reverse OM is the more representative behavioural signature of mental arithmetic.

Original languageEnglish
Pages (from-to)536-547
Number of pages12
JournalQuarterly Journal of Experimental Psychology
Issue number3
StatePublished - Mar 2021


  • Heuristics and biases
  • SNARC effect
  • mental arithmetic
  • operational momentum


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