THE ROUGH GUIDE TO PSYCHOLOGYOn the other hand, they can read most words that they know “whole”,
without having to decode them letter by letter. By contrast, other patients
have surface dyslexia and show the opposite pattern of impairment:
they can read words letter by letter, but they can’t read words “whole”.
This means they come unstuck with irregular words, such as “yacht”,
that don’t obey the normal letter-to-sound correspondence rules. Taken
together, these and other findings suggest we have at least two routes for
processing words – one is by whole word or lexicon, while the other is
piecemeal, letter by letter.
Another condition caused by brain damage is the inability to dig
up the right word for objects, places or concepts, known as “anomia”.
Curiously, anomia can affect some categories of words but not others. A
patient might be able to name objects, for example, but not living things.
Finding the right words for things obviously depends in part on our
semantic memory – our knowledge about the world. A 2009 study by
Faye Corbett, at the University of Manchester, took this idea further by
suggesting that the brain’s semantic system is comprised of two parts: a
core store of knowledge in the temporal lobes, and a search-and-control
system, embodied in the frontal cortex and temporo-parietal junc-
tion, which navigates through the corridors of the mind finding and
comparing word meanings.
A language switch?
Why don’t people who are bilingual or multilingual get confused more
often, flitting back and forth between their different languages? A
popular view is that they have a neural switch at the front of the brain
that shuts down languages that aren’t currently in use. This idea found
support in a 2007 study, led by Khuan Ko and his team at the University
Medical Centre in Utrecht, which involved probing the brains of
people undergoing surgery for epilepsy. The principal purpose of
such probing is to ensure that the surgeons don’t cut the wrong bits
of the brain, but it also provides a rare opportunity for experimenta-
tion. In one case a French-Chinese bilingual was asked to count as the
researchers prodded his brain looking for language regions. The man
began counting in French, then when he reached seven (...quatre, cinq,
six, sept), the stimulation was applied to the lower, left-hand side of the
front of his brain, at which point he involuntarily switched to Chinese
(...ba, jiu, shi). When the stimulation ended, he reverted to French. It’s
as though the researchers had accidentally flipped the switch that
inhibits whichever language isn’t in use.