:''This article refers to the neurological phenomenon. For Unicode numbers, see
Number Forms
Number Forms is a Unicode block containing Unicode compatibility characters that have specific meaning as numbers, but are constructed from other characters. They consist primarily of vulgar fractions and Roman numerals. In addition to the cha ...
.''
A number form is a mental map of
number
A number is a mathematical object used to count, measure, and label. The original examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can be represented in language with number words. More universally, individual numbers c ...
s, which
automatically 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 by Sir
Francis Galton
Sir Francis Galton, FRS FRAI (; 16 February 1822 – 17 January 1911), was an English Victorian era polymath: a statistician, sociologist, psychologist, anthropologist, tropical explorer, geographer, inventor, meteorologist, proto- ...
in his ''The Visions of Sane Persons'' . Later research has identified them as a type of
synesthesia
Synesthesia (American English) or synaesthesia (British English) is a perceptual phenomenon in which stimulation of one sensory or cognitive pathway leads to involuntary experiences in a second sensory or cognitive pathway. People who re ...
(; ).
Neural mechanisms
It has been suggested that number-forms are a result of "cross-activation" between regions of the
parietal lobe
The parietal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The parietal lobe is positioned above the temporal lobe and behind the frontal lobe and central sulcus.
The parietal lobe integrates sensory informa ...
that are involved in
numerical cognition
Numerical cognition is a subdiscipline of cognitive science that studies the cognitive, developmental and neural bases of numbers and mathematics. As with many cognitive science endeavors, this is a highly interdisciplinary topic, and includes r ...
and angular gyrus for spatial cognition (; ). Since the areas that process numerical and spatial representations are close to each other, this may contribute to the increased cross-activation. Compared to non-synesthetes,
synesthetes display larger
P3b
The P3b is a subcomponent of the P300, an event-related potential (ERP) component that can be observed in human scalp recordings of brain electrical activity. The P3b is a positive-going amplitude (usually relative to a reference behind the ear ...
amplitudes for month cues, but similar
N1 and P3b responses for arrow (<- or ->) and word (left or right) cues. ().
Reaction time research
Reaction time
Mental chronometry is the scientific study of processing speed or reaction time on cognitive tasks to infer the content, duration, and temporal sequencing of mental operations. Reaction time (RT; sometimes referred to as "response time") is meas ...
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 (; ). This can be thought of as a "spatial
Stroop Stroop is a Dutch surname. Notable people with the name include:
* John Ridley Stroop (1897–1973), American psychologist, after whom the Stroop effect was named
* Jürgen Stroop
Jürgen Stroop (born Josef Stroop, 26 September 1895 – 6 Marc ...
" 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 ().
Differences with number line
These number forms can be distinguished from the non-conscious mental
number lines by the fact that they are 1)
conscious
Consciousness, at its simplest, is sentience and awareness of internal and external existence. However, the lack of definitions has led to millennia of analyses, explanations and debates by philosophers, theologians, linguisticians, and scien ...
, 2)
idiosyncratic
An idiosyncrasy is an unusual feature of a person (though there are also other uses, see below). It can also mean an odd habit. The term is often used to express eccentricity or peculiarity. A synonym may be "quirk".
Etymology
The term "idiosyncra ...
(see image) and 3) stable across the lifespan. Although this form of synesthesia has not been as intensively studied as
Grapheme → color synesthesia, Hubbard and colleagues have argued that similar neural mechanisms might be involved, but acting in different brain regions (). Future studies will need to be conducted to test this hypothesis.
See also
*
Synesthesia
Synesthesia (American English) or synaesthesia (British English) is a perceptual phenomenon in which stimulation of one sensory or cognitive pathway leads to involuntary experiences in a second sensory or cognitive pathway. People who re ...
*
Ideasthesia
Ideasthesia (alternative spelling ideaesthesia) is a neuropsychological phenomenon in which activations of concepts (inducers) evoke perception-like sensory experiences (concurrents). The name comes from the Ancient Greek () and (), meaning 'se ...
*
Aphantasia
Aphantasia ( , ) is the inability to create mental imagery.
The phenomenon was first described by Francis Galton in 1880 but has since remained relatively unstudied. Interest in the phenomenon renewed after the publication of a study in 2015 c ...
References
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Synesthesia
Cognitive science