Multiple left-to-right spatial representations of number magnitudes? Evidence from left spatial neglect

  • Jean-Philippe van DijckEmail author
  • Fabrizio Doricchi
Research Article


The SNARC effect reflects the observation that when healthy observers with left-to-right reading habits are asked to compare the magnitude or to judge the parity of numbers, they provide faster reaction times (RT) to small numbers with left-sided responses and faster RTs to large numbers with right-sided responses. In magnitude comparison (MC), right brain damaged patients with left-sided neglect typically show a pathologically enlarged SNARC for large numbers and selective slowing to numbers that are immediately lower than the numerical reference (e.g. 4 for reference 5). This asymmetry has been taken as evidence that small numbers are mentally positioned to the left of the reference and, therefore, are processed less efficiently by patients neglecting the left side of space. In parity judgement (PJ), on the other hand, the size of the SNARC effect is unaffected by neglect. This dissociation is typically attributed to the disturbed explicit processing of number magnitude in MC and preserved implicit processing of magnitude in PJ. Before accepting this interpretation, however, it remains to be investigated whether neglect patients show the same RT pattern that characterizes the performance of healthy participants (i.e. left-side RTs that increase linearly as a function of number magnitude and right-side RTs that decrease linearly as a function of magnitude). Clarifying this point is crucial, because an equally sized SNARC can originate from different RT patterns. Here we demonstrate that the RT pattern of neglect patients during PJ is entirely comparable to those of patients without neglect and healthy controls, while the same neglect patients show selective slowing to numbers that are immediately lower than the numerical reference in MC. These findings suggest the existence of multiple left-to-right spatial representations of number magnitude and provides an explanation of the functional dissociation between MC and PJ tasks.


SNARC effect Distance effect Spatial neglect Spatial codes 



We would like to thank Mario Pinto and Michelle Pellegrino for their help in testing additional patients.


  1. Abrahamse E, van Dijck J-P, Majerus S, Fias W (2014) Finding the answer in space: the mental whiteboard hypothesis on serial order in working memory. Front Hum Neurosci 8:932. Google Scholar
  2. Abrahamse E, van Dijck JP, Fias W (2016) How does working memory enable number-induced spatial biases? Front Psychol 7:977Google Scholar
  3. Abrahamse EL, van Dijck JP, Fias W (2017) Grounding verbal working memory: the case of serial order. Curr Dir Psychol Sci 26(5):429–433Google Scholar
  4. Aiello M, Jacquin-Courtois S, Merola S, Ottaviani T, Tomaiuolo F, Bueti D, Doricchi F (2012) No inherent left and right side in human ‘mental number line’: evidence from right brain damage. Brain 135(8):2492–2505Google Scholar
  5. Antoine S, Ranzini M, Dijck JP, Slama H, Bonato M, Tousch A et al (2018) Hemispatialneglect and serial order in verbal working memory. J Neuropsychol. Google Scholar
  6. Azouvi P, Samuel C, Louis-Dreyfus A, Bernati T, Bartolomeo P, Beis JM, De Montety G (2002) Sensitivity of clinical and behavioural tests of spatial neglect after right hemisphere stroke. J Neurol Neurosurg Psychiatry 73(2):160–166Google Scholar
  7. Berti A, Rizzolatti G (1992) Visual processing without awareness: evidence from unilateral neglect. J Cogn Neurosci 4(4):345–351Google Scholar
  8. Binder J, Marshall R, Lazar R, Benjamin J, Mohr JP (1992) Distinct syndromes of hemineglect. Arch Neurol 49(11):1187–1194Google Scholar
  9. Dehaene S (1997) The number sense: how the mind creates mathematics. Oxford University Press, New YorkGoogle Scholar
  10. Dehaene S, Bossini S, Giraux P (1993) The mental representation of parity and number magnitude. J Exp Psychol Gen 122(3):371–396Google Scholar
  11. Doricchi F, Incoccia C, Galati G (1997) Influence of figure-ground contrast on the implicit and explicit processing of line drawings in patients with left unilateral neglect. Cogn Neuropsychol 14(4):573–594Google Scholar
  12. Fattorini E, Pinto M, Rotondaro F, Doricchi F (2015) Perceiving numbers does not cause automatic shifts of spatial attention. Cortex 73:298–316Google Scholar
  13. Fattorini E, Pinto M, Merola S, D’ Onofrio M, Doricchi F (2016) On the instability and constraints of the interaction between number representation and spatial attention in healthy humans: a concise review of the literature and new experimental evidence. Prog Brain Res 227:223–256Google Scholar
  14. Fias W, Fischer MH (2005) Spatial representation of number. In: Campbell JID (ed) Handbook of mathematical cognition. Psychology Press, Hove, pp 43–54Google Scholar
  15. Fias W, van Dijck J-P (2016) The temporary nature of number—space interactions. Can J Exp Psychol 70(1):33–40Google Scholar
  16. Fias W, Brysbaert M, Geypens F, d’Ydewalle G (1996) The importance of magnitude information in numerical processing: evidence from the SNARC effect. Math Cogn 2(1):95–110Google Scholar
  17. Fink GR, Marshall JC, Shah NJ, Weiss PH, Halligan PW, Grosse-Ruyken M, Freund HJ (2000) Line bisection judgments implicate right parietal cortex and cerebellum as assessed by fMRI. Neurology 54(6):1324–1331Google Scholar
  18. Fischer MH, Castel AD, Dodd MD, Pratt J (2003) Perceiving numbers causes spatial shifts of attention. Nat Neurosci 6(6):555–556Google Scholar
  19. Gainotti G, De Luca L, Figliozzi F, Doricchi F (2009) The influence of distracters, stimulus duration and hemianopia on first saccade in patients with unilateral neglect. Cortex 45(4):506–516Google Scholar
  20. Gauthier L, Dehaut F, Joanette Y (1989) The bells test—A quantitative and qualitative test for visual neglect. Int J Clin Neuropsychol 11(2):49–54Google Scholar
  21. Gevers W, Ratinckx E, De Baene W, Fias W (2006) Further evidence that the SNARC effect is processed along a dual-route architecture—evidence from the lateralized readiness potential. Exp Psychol 53(1):58–68Google Scholar
  22. Gevers W, Santens S, Dhooge E, Chen Q, Fias W, Verguts T (2010) Verbal-spatial and visuo-spatial coding of number–space interactions. J Exp Psychol Gen 139(1):180–190Google Scholar
  23. Herrera A, Macizo P, Semenza C (2008) The role of working memory in the association between number magnitude and space. Acta Psychologica 128(2):225–237Google Scholar
  24. Hubbard EM, Piazza M, Pinel P, Dehaene S (2005) Interactions between number and space in parietal cortex. Nat Rev Neurosci 6(6):435–448Google Scholar
  25. Jacob S, Nieder A (2008) The ABC of cardinal and ordinal number representations. Trends Cogn Sci 12(2):41–43Google Scholar
  26. Jager G, Postma A (2003) On the hemispheric specialization for categorical and coordinate spatial relations: a review of the current evidence. Neuropsychologia 41(4):504–515Google Scholar
  27. Kim S-Y, Kim M-S, Chun MM (2005) Concurrent working memory load can reduce distraction. Proc Natl Acad Sci USA 102(45):16524–16529Google Scholar
  28. Kosslyn SM (1987) Seeing and imagining in the cerebral hemispheres—a computational approach. Psychol Rev 94(2):148–175Google Scholar
  29. Lavie N, Hirst A, de Fockert JW, Viding A (2004) Load theory of selective attention and cognitive control. J Exp Psychol Gen 133(3):339–354Google Scholar
  30. Lorch RF, Myers JL (1990) Regression-analyses of repeated measures data in cognitive research. J Exp Psychol Learn Mem Cogn 16(1):149–157Google Scholar
  31. Marshall JC, Halligan PW (1988) Blindsight and insight in visuo-spatial neglect. Nature 336(6201):766Google Scholar
  32. Pinto M, Fattorini E, Lasaponara S, D’Onofrio M, Fortunato G, Doricchi F (2018) Visualising numerals: a ERPs study with the attentional SNARC task. Cortex 101:1–15Google Scholar
  33. Priftis K, Zorzi M, Meneghello F, Marenzi R, Umilta C (2006) Explicit versus implicit processing of representational space in neglect: dissociations in accessing the mental number line. J Cogn Neurosci 18(4):680–688Google Scholar
  34. Proctor RW, Cho YS (2006) Polarity correspondence: a general principle for performance of speeded binary classification tasks. Psychol Bull 132(3):416–442Google Scholar
  35. Rorden C, Karnath HO (2010) A simple measure of neglect severity. Neuropsychologia 48(9):2758–2763Google Scholar
  36. Rossetti Y, Jacquin-Courtois S, Aiello M, Ishihara M, Brozzoli C, Doricchi F (2011) Neglect “around the clock”: dissociating number and spatial neglect in right brain damage. In: Dehaene S, Brannon EM (eds) Space, time and number in the brain: Searching for the foundations of mathematical thought. Academic Press, Burlington, MA, pp 149–173Google Scholar
  37. Schwarz W, Keus IM (2004) Moving the eyes along the mental number line: comparing SNARC effects with saccadic and manual responses. Percept Psychophys 66(4):651–664Google Scholar
  38. Van Opstal F, Gevers W, De Moor W, Verguts T (2008) Dissecting the symbolic distance effect: comparison and priming effects in numerical and nonnumerical orders. Psychon Bull Rev 15(2):419–425Google Scholar
  39. van Dijck J-P, Gevers W, Fias W (2009) Numbers are associated with different types of spatial information depending on the task. Cognition 113(2):248–253Google Scholar
  40. van Dijck J-P, Gevers W, Lafosse C, Fias W (2012) The heterogeneous nature of number–space interactions. Front Hum Neurosci 5:182Google Scholar
  41. van Dijck JP, Ginsburg V, Girelli L, Gevers W (2015) Linking numbers to space: from themental number line towards a hybrid account. In: Cohen Kadosh R, Dowker A (eds) The Oxford handbook of mathematical cognition. Oxford University Press, Oxford, UK, pp 89–105Google Scholar
  42. Verdon V, Schwartz S, Lovblad KO, Hauert CA, Vuilleumier P (2009) Neuroanatomy of hemispatial neglect and its functional components: a study using voxel-based lesion-symptom mapping. Brain 133(3):880–894Google Scholar
  43. Vuilleumier P, Ortigue S, Brugger P (2004) The number space and neglect. Cortex 40(2):399–410Google Scholar
  44. Zorzi M, Bonato M, Treccani B, Scalambrin G, Marenzi R, Priftis K (2012) Neglect impairs explicit processing of the mental number line. Front Hum Neurosci 6:125Google Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of Experimental PsychologyGhent UniversityGhentBelgium
  2. 2.Department of Applied PsychologyThomas More University of Applied SciencesAntwerpBelgium
  3. 3.Department of PsychologyRome University “La Sapienza”RomeItaly
  4. 4.Fondazione Santa Lucia-IRCCS RomeRomeItaly

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