Congenitally blind visualise numbers back to front

A person with normal sight will imagine a left to right “number line” with the smallest number first. A congenitally blind person’s number line is visualised right to left.

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The University of Bath has recently discovered that congenitally
blind people visualise numbers in the opposite direction to sighted
people.

In what they claim to be a world first, researchers from the
university's Department of Psychology were shocked to discover that
visualised lines of numbers in the congenitally blind moved from
right to left, rather than left to right -- with the larger numbers
on the left and the smaller numbers on the right.

A person with normal sight will imagine a left to right "number
line" with the smallest number first: 1, 2, 3, 4, 5. The
congenitally blind's number line however is visualised right to
left: 5, 4, 3, 2, 1.

Dr Michael Proulx, a senior lecturer from the Department of
Psychology, explained: "Our unexpected results relate to the fact
that people who were born visually impaired like to map the
position of objects in relation to themselves… it is likely that
this style of spatial representation extends to numbers too, and
the right-handed participants mapped the number line from their
dominant right hand."

The researchers were able to "see" their participant's
visualised number lines by requesting the subjects look either left
or right as they (the subjects) vocalised random numbers. The team
-- which reached as far as Sabanci University in Turkey and Taisho
University in Japan -- then compared the responses of the
congenitally blind in conjunction with those who had been born with
vision before losing their sight (the adventitiously
blind) and the fully sighted, but blindfolded volunteers.

Past studies have shown individuals who come from cultures in
which their writing flows from right to left also visualise their
numbers similarly. However, this is the first example, claims the
university, in which a number line is visualised right to left by
blind individuals from a western culture.

Dr Proulx remarked:
"Remembering and representing numbers is an important skill, and
the foundation of mental maths. Visually impaired people are just
as good, if not better, at mathematics than sighted people -- Royal
Society Fellow Nicholas
Saunderson is one famous example.

"What makes this work exciting is that Saunderson may have been
able to advance mathematics with an entirely different mental
representation of numbers than that of sighted contemporaries like
Isaac Newton."

The full results of the study, Sensory deprivation: visual
experience alters the mental number line, will be published in
the journal Behavioural Brain Research.