Can approximate mental calculation account for operational momentum in addition and subtraction?

André Knops, Stanislas Dehaene, Ilaria Berteletti, Marco Zorzi

Research output: Contribution to journalArticlepeer-review


The operational momentum (OM) effect describes a cognitive bias whereby we overestimate the results of mental addition problems while underestimating for subtraction. To test whether the OM emerges from psychophysical characteristics of the mental magnitude representation we measured two basic parameters (Weber fraction and numerical estimation accuracy) characterizing the mental magnitude representation and participants' performance in cross-notational addition and subtraction problems. Although participants were able to solve the cross-notational problems, they consistently chose relatively larger results in addition problems than in subtraction problems, thus replicating and extending previous results. Combining the above measures in a psychophysical model allowed us to partially predict the chosen results. Most crucially, however, we were not able to fully model the OM bias on the basis of these psychophysical parameters. Our results speak against the idea that the OM is due to basic characteristics of the mental magnitude representation. In turn, this might be interpreted as evidence for the assumption that the OM effect is better explained by attentional shifts along the mental magnitude representation during mental calculation.

Original languageEnglish
Pages (from-to)1541-1556
Number of pages16
JournalQuarterly Journal of Experimental Psychology
Issue number8
Publication statusPublished - 2014


  • Approximate number system
  • Attention
  • Mental number line
  • Operational momentum
  • Weber fraction

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)
  • Psychology(all)
  • Experimental and Cognitive Psychology
  • Neuropsychology and Physiological Psychology
  • Medicine(all)


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