A number form is a
mental map of
number
A number is a mathematical object used to count, measure, and label. The most basic 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 can ...
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 (; 16 February 1822 – 17 January 1911) was an English polymath and the originator of eugenics during the Victorian era; his ideas later became the basis of behavioural genetics.
Galton produced over 340 papers and b ...
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 with sy ...
.
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 Lobes of the brain, 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 integra ...
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 re ...
and
angular gyrus
The angular gyrus is a region of the brain lying mainly in the posteroinferior region of the parietal lobe, occupying the posterior part of the inferior parietal lobule. It represents the Brodmann area 39.
Its significance is in transferring vis ...
for
spatial cognition
In cognitive psychology, spatial cognition is the acquisition, organization, utilization, and revision of knowledge about spatial environments. It is most about how animals, including humans, behave within space and the knowledge they built aroun ...
.
Since the areas that process numerical and spatial representations are close to each other, this may contribute to the increased cross-activation.
Synesthetes display larger
P3b amplitudes for month cues compared to non-synesthetes, 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; also referred to as "response time") is measured ...
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.
[
]
Differences with number line
These number forms can be distinguished from the non-conscious mental number line
A number line is a graphical representation of a straight line that serves as spatial representation of numbers, usually graduated like a ruler with a particular origin point representing the number zero and evenly spaced marks in either dire ...
s by the fact that they are conscious
Consciousness, at its simplest, is awareness of a state or object, either internal to oneself or in one's external environment. However, its nature has led to millennia of analyses, explanations, and debate among philosophers, scientists, a ...
, idiosyncratic
An idiosyncrasy is a unique feature of something. The term is often used to express peculiarity.
Etymology
The term "idiosyncrasy" originates from Greek ', "a peculiar temperament, habit of body" (from ', "one's own", ', "with" and ', "blend ...
and stable across the person's lifespan. Although this form of synesthesia has not been as intensively studied as grapheme–color synesthesia
Grapheme–color synesthesia or colored grapheme synesthesia is a form of synesthesia in which an individual's perception of numerals and letters is associated with the experience of colors. Like all forms of synesthesia, grapheme–color synesthe ...
, Hubbard and colleagues have argued that similar neural mechanisms might be involved, but acting in different brain regions.[
]
See also
*Aphantasia
Aphantasia ( , ) is the inability to voluntarily visualize mental images.
The phenomenon was first described by Francis Galton in 1880, but has remained relatively unstudied. Interest in the phenomenon renewed after the publication of a study ...
*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 ...
*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 with sy ...
References
{{reflist
Synesthesia
Cognitive science