# Number form

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{{Use American English|date = February 2019}}
{{Short description|Mental map of numbers}}
{{about|the neurological phenomenon|Unicode numbers|Number Forms}}
{{Technical|date=November 2019}}
thumb|upright=1.3|A number form from one of Francis Galton's (1888) subjects. Note the convolutions, and how the first 12 digits correspond to a clock face. Number forms are idiosyncratic to the person experiencing them.

A '''number form''' is a [mental map](/source/mental_map) of [number](/source/number)s, which [automatically](/source/Automaticity) and involuntarily appears whenever someone who experiences number-forms thinks of numbers. Numbers are mapped into distinct spatial locations and the mapping may be different across individuals. Number forms were first documented and named in 1881 by Sir [Francis Galton](/source/Francis_Galton) in his ''The Visions of Sane Persons''.<ref>{{cite book |last1=Galton |first1=Francis |title=The Visions of Sane Persons |date=1881 |url=https://galton.org/cgi-bin/searchImages/search/essays/pages/galton-1881-fort-rev-visions-sane-persons_2.htm}}</ref> Later research has identified them as a type of [synesthesia](/source/synesthesia).<ref>{{cite journal |last1=Seron |first1=X. |last2=Pesenti |first2=M. |last3=Noël |first3=M. P. |last4=Deloche |first4=G. |last5=Cornet |first5=J. A. |title=Images of numbers, or "When 98 is upper left and 6 sky blue" |journal=Cognition |date=August 1992 |volume=44 |issue=1–2 |pages=159–196 |doi=10.1016/0010-0277(92)90053-k |pmid=1511585 |s2cid=26687757 |issn=0010-0277}}</ref><ref name=Sagiv>{{cite journal |last1=Sagiv |first1=Noam |last2=Simner |first2=Julia |last3=Collins |first3=James |last4=Butterworth |first4=Brian |last5=Ward |first5=Jamie |title=What is the relationship between synaesthesia and visuo-spatial number forms? |journal=Cognition |date=August 2006 |volume=101 |issue=1 |pages=114–128 |doi=10.1016/j.cognition.2005.09.004 |pmid=16288733 |s2cid=1948034 |issn=0010-0277}}</ref>

== Neural mechanisms ==
It has been suggested that number-forms are a result of cross-activation between regions of the [parietal lobe](/source/parietal_lobe) that are involved in [numerical cognition](/source/Numerical_Cognition) and [angular gyrus](/source/angular_gyrus) for [spatial cognition](/source/spatial_cognition).<ref>{{cite journal |last1=Ramachandran |first1=V. S. |last2=Hubbard |first2=E. M. |title=Synaesthesia—A Window Into Perception, Thought and Language |journal=Journal of Consciousness Studies |volume=8 |issue=12 |pages=3–34 |date=2001 |url=http://psy.ucsd.edu/~edhubbard/papers/JCS.pdf |access-date=2018-02-27 |archive-date=2006-05-27 |archive-url=https://web.archive.org/web/20060527085838/http://psy.ucsd.edu/~edhubbard/papers/JCS.pdf |url-status=dead }}</ref><ref name=Hubbard>{{cite journal |last1=Hubbard |first1=Edward M. |last2=Piazza |first2=Manuela |last3=Pinel |first3=Philippe |last4=Dehaene |first4=Stanislas |title=Interactions between number and space in parietal cortex |journal=Nature Reviews. Neuroscience |date=June 2005 |volume=6 |issue=6 |pages=435–448 |doi=10.1038/nrn1684 |pmid=15928716 |s2cid=1465072 |issn=1471-003X}}</ref> Since the areas that process numerical and spatial representations are close to each other, this may contribute to the increased cross-activation. [Synesthete](/source/Synesthete)s display larger [P3b](/source/P3b) amplitudes for month cues compared to non-synesthetes, but similar [N1](/source/Visual_N1) and P3b responses for arrow (← or →) and word (left or right) cues.<ref name=Teuscher>{{cite journal |last1=Teuscher |first1=Ursina |last2=Brang |first2=David |last3=Ramachandran |first3=Vilayanur S. |last4=Coulson |first4=Seana |title=Spatial cueing in time-space synesthetes: An event-related brain potential study |journal=Brain and Cognition |date=October 2010 |volume=74 |issue=1 |pages=35–46 |doi=10.1016/j.bandc.2010.06.001 |pmid=20637536 |s2cid=15082643 |issn=1090-2147}}</ref>

== Reaction time research ==
[Reaction time](/source/Reaction_time) studies have shown that number-form synesthetes are faster to say which of two numbers is larger when the numbers are arranged in a manner consistent with their number-form, suggesting that number forms are automatically evoked.<ref name=Sagiv/><ref name=Piazza>{{cite journal |last1=Piazza |first1=M. |last2=Pinel |first2=P. |last3=Dehaene |first3=S. |title=Objective correlates of an unusual subjective experience: A single-case study of number-form synaesthesia |journal=Cognitive Neuropsychology |date=1 December 2006 |volume=23 |issue=8 |pages=1162–1173 |doi=10.1080/02643290600780080 |pmid=21049372 |s2cid=12570398 |issn=0264-3294}}</ref> This can be thought of as a spatial [Stroop](/source/Stroop_effect) task, in which space is not relevant to the task, but which can hinder performance despite its irrelevance.  The fact that synesthetes cannot ignore the spatial arrangement of the numbers on the screen demonstrates that numbers are automatically evoking spatial cues. The reaction times for valid cues are smaller than invalid cues (words and arrows), but in synesthetes the response time differences for months are larger than those of non-synesthetes.<ref name=Teuscher/>

== Differences with number line ==
These number forms can be distinguished from the non-conscious mental [number line](/source/number_line)s by the fact that they are [conscious](/source/conscious), [idiosyncratic](/source/idiosyncratic) and stable across the person's lifespan. Although this form of synesthesia has not been as intensively studied as [grapheme–color synesthesia](/source/grapheme%E2%80%93color_synesthesia), Hubbard and colleagues have argued that similar neural mechanisms might be involved, but acting in different brain regions.<ref name=Hubbard/>

== See also ==
*[Aphantasia](/source/Aphantasia)
*[Ideasthesia](/source/Ideasthesia)
*[Synesthesia](/source/Synesthesia)

== References ==
{{reflist}}

Category:Synesthesia
Category:Cognitive science

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Adapted from the Wikipedia article [Number form](https://en.wikipedia.org/wiki/Number_form) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Number_form?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.