03 June 2013 by Charles Fernyhough
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IT CAN happen anywhere. I can be
driving, walking by the river or sitting quietly in front of a blank
screen. Sometimes suddenly, sometimes gradually and imperceptibly, I
become conscious of words that no one else can hear, telling me things,
guiding me, evaluating my actions. I am doing something perfectly
ordinary – I am thinking– and it takes the form of a voice in my head.
If you ask people to reflect on their
own stream of consciousness, they often describe experiences like this.
Usually termed inner speech, it is also referred to as the inner voice,
internal monologue or dialogue, or verbal thought. But although
philosophers have long been interested in the relationship between
language and thought, many believed that inner speech lay outside the
realms of science. That is now changing, with new experimental designs
for encouraging it, interfering with it and neuroimaging it. We are
beginning to understand how the experience is created in the brain; its
subjective qualities – essentially, what the words "sound" like; and its
role in processes such as self-control and self-awareness. The voice in
our head is finally revealing its secrets, and it is just as powerful
as you might have imagined.
Much of modern research has been inspired by the long-neglected theories of L. S. Vygotsky,
a Russian psychologist whose career unfolded in the early days of the
Soviet Union. Vygotsky only studied psychology for about 10 years before
his untimely death from tuberculosis in his late thirties – a fact that
has led some to call him "the Mozart of psychology". Starting with
observations of children talking to themselves while playing, Vygotsky
hypothesised that this "private speech" develops out of social dialogue
with parents and caregivers. Over time, these private mutterings become
further internalised to form inner speech.
If Vygotsky was right, inner speech
should have some very special properties. Because it develops from
social interactions, it should take on some of the qualities of a
dialogue, an exchange between different points of view. Vygotsky also
proposed that inner speech undergoes some important transformations as
it becomes internalised, such as becoming abbreviated or condensed
relative to external speech. For instance, when hearing a loud metallic
sound outside at night and realising that the cat is to blame, you
probably wouldn't say to yourself, "The cat has knocked the dustbin
over." Instead, you might just say, "The cat," since that utterance
contains all the information you need to express to yourself.
Partly because Vygotsky's work was
suppressed by the Soviet authorities, it was a long time before his
ideas became well known in the West, and even longer before researchers
tested whether people actually report these qualities in their inner
speech. In the first such study, conducted in 2011 at Durham University,
UK, my colleague Simon McCarthy-Jones and I found that 60 per cent of
people report that their inner speech has the to-and-fro quality of a
conversation.
Eavesdropping on thoughts
So-called "self-report" methods have
their limitations, not least that people are being asked to comment
retrospectively on their inner experience. Another method, offering a
richer picture of people's thoughts during a particular time period, was
developed by psychologist Russell Hurlburt
at the University of Nevada, Las Vegas. It involves participants being
trained to give very detailed descriptions of their own inner experience
in response to random cues from a beeper. Such studies have shown that
people often report a train of thought unfolding more quickly than
circumstances ought to have allowed, and yet not seeming rushed, which
could be taken as evidence for the compression of sentences that
Vygotsky postulated.
Vygotsky's theory also suggests some
possibilities about the way inner speech is created in the brain. If it
is derived from external speech, as he proposed, both might be expected
to activate the same neural networks. Sure enough, long after his death,
fMRI studies have linked inner speech to the left inferior frontal
gyrus, including a region called Broca's area, which is known to be
important for speech production.
Quite how much our inner and outer
speech overlap remains a matter of debate. According to one view, inner
speech is just external speech without articulation: the brain plans an
utterance, but stops short of kicking our muscles into action. If that
is the case, our internal voice should resonate with the same qualities
of tone, timbre and accent as our ordinary external speech.
There are some hints that this may be
the case. In their lab at the University of Nottingham, UK,
psychologists Ruth Filik and Emma Barber recently asked participants to read limericks silently in their heads. One was: There
was a young runner from Bath, Who stumbled and fell on the path; She
didn't get picked, As the coach was quite strict, So he gave the
position to Kath.
The other limerick read: There was
an old lady from Bath, Who waved to her son down the path; He opened the
gates, And bumped into his mates, Who were Gerry, and Simon, and Garth.
Importantly, some of the participants
had northern English accents, with short vowels (pronouncing "Bath" to
rhyme with "Kath"), while the others had the long vowels of a southern
accent ("Bath" rhyming with "Garth"). By tracking the volunteers'
eye-movements, the researchers showed that reading was disrupted when
the final word of the limerick did not rhyme in that volunteer's accent –
when a southerner read "Bath" then "Kath", for instance. Although this
study suggests that inner speech does indeed have an accent – and
presumably other qualities of our spoken voice – one concern is that the
inner speech we produce when reading is not necessarily the same thing
as our everyday, spontaneous inner speech, which means that more
naturalistic studies are needed.
So much for the subjective qualities
of inner speech. What, if anything, does it actually do? Vygotsky
proposed that words in inner speech function as psychological tools that
transform the task in question, just as the use of a screwdriver
transforms the task of assembling a shed. Putting our thoughts into
words gives them a more tangible form which makes them easier to use. It
may also be that verbal thought can allow communication between other
cognitive systems, effectively providing a common language for the
brain.
One of Vygotsky's most enticing
predictions was that private and inner speech give us a way of taking
control of our own behaviour, by using words to direct our actions.
While driving up to a roundabout in busy traffic, for example, I'll
still tell myself, "Give way to the right", especially if I've just been
driving overseas. Knocking out the systems responsible for inner speech
should therefore impede our performance on certain tasks that require
planning and control, offering a powerful test of the hypothesis.
Such experiments typically require
participants to repeat a word to themselves out loud to suppress their
verbal thoughts while they perform a task (a technique known as
articulatory suppression). Using this set-up, Jane Lidstone, one of my
colleagues at Durham University, looked at the performance of children
aged 7 to 10 on a planning task known as the Tower of London, which
involves moving coloured balls around between three sticks of differing
lengths in order to match a given pattern. Lidstone found that children
performed worse if they had to repeat a word out loud,
compared with trials in which they instead tapped repetitively with one
of their feet. Similar findings have emerged from studies with adults.
Alexa Tullett and Michael Inzlicht of the University of Toronto in
Canada gave student participants a classic test of control known as the Go/No-Go task,
which required them to press a button the moment they saw a yellow
square pop up on the screen, but to remain still when they saw a purple
square. It is a considerable test of impulse control, and, as predicted,
the students were less accurate
during articulatory suppression, compared with when they were doing a
spatial task. Although experiments like these seem artificial, they
allow researchers the kind of control over conditions that good science
demands to test something like self-control.
Pep talks
So we know that inner speech has a
role in regulating behaviour, but could it also have a role in
motivating it? The research on children's private speech (Vygotsky's
precursor of inner speech, remember) shows that it frequently has an
emotional or motivational flavour. Athletes often give themselves pep
talks before, during and after performances. In our study of the quality
of inner speech, McCarthy-Jones and I found that two-thirds of students
reported using internal speech that either evaluated their behaviour or
served to motivate it.
Inner speech may even help us to
become aware of who we are as individuals. Some philosophers have
proposed that awareness of inner speech is important for understanding
our own mental processes, an aspect of what psychologists call
metacognition. Children typically do not become aware of their own inner
speech until around age 4, although it is uncertain whether that
reflects their inability to reflect on their own thought processes, or
the fact that inner speech is not yet fully internalised by that age. At
Mount Royal University in Calgary, Canada, psychologist Alain Morin
has found that people who use inner speech more often show better
self-understanding. "Inner speech allows us to verbally analyse our
emotions, motives, thoughts and behavioural patterns," he says. "It puts
to the forefront of consciousness what would otherwise remain mostly
subconscious."
While researchers are still gathering
the evidence, these results certainly suggest that the voice in the head
is important to many cognitive processes. But what about people who,
for various reasons, don't talk to themselves in the usual way? As you
might expect, deaf people who communicate in sign language often talk to
themselves in sign too. People with autism, meanwhile, who often have
problems with linguistic communication, seem not to use inner speech for
planning, although they do use it for other purposes such as short-term
memory. A more dramatic difficulty comes from damage to the language
areas of the brain, which can silence some people's inner voices. One
such individual, neuroanatomist Jill Bolte Taylor, reported a lack of self-awareness after a stroke that damaged her language system – supporting Morin's view that verbal thinking may be important for self-understanding.
Lending an ear to the differences
between people might also tell us more about the dark side of inner
speech, following a growing understanding that our internal monologue is
not always beneficial to our well-being. When we worry and ruminate, we
often do it in words, and our inner speech may contribute to anxiety
and depression by keeping thoughts in the head that would be better off
discarded. Inner speech may play its biggest role, however, in an
experience that is often associated with other forms of mental disorder.
People with certain psychiatric diagnoses (particularly schizophrenia),
but also a small minority of people who do not have a mental illness,
report the experience of hearing a person speak when there is no one
present. Voice-hearing, or auditory verbal hallucination, is an
enigmatic phenomenon whose cognitive and neural bases are not yet well
understood. One prominent theory proposes that it occurs because the
individual produces an utterance in inner speech that they do not
recognise as their own. The result is that a bit of speech that was
actually self-generated becomes attributed to another person: an alien
voice.
Various lines of evidence converge to
support this view. An early observation was that people who hear voices
produce very slight activation in their articulatory muscles when their
voices occur. Cognitive behaviour therapy to treat voice-hearing often
focuses on blocking the phonological loop, by articulatory suppression
or listening to music, so that the rogue inner speech cannot be
generated. But the phenomenon of voice-hearing is undoubtedly more
complicated than this. McCarthy-Jones, now at Macquarie University in
New South Wales, Australia, notes that "while inner speech appears to be
the basis of some voices, others are actual or mutated memories of
earlier life-events (often traumatic ones)". Many researchers,
particularly those associated with the worldwide hearingthevoice.org/looking-for-support
Hearing Voices Movement, now believe that voices have important
meanings for the individual, and therefore that they need to be
understood rather than suppressed.
A shower of words
There is much more we need to learn
about inner speech's roles in our thinking and behaviour. Some insights
may come from people who, without any disability, don't report any inner
speech at all. For some of these people, it may be that inner speech is
present, but that it is so condensed and abbreviated that it no longer
seems very like language. It will also be interesting to note the
consequences when people try to suppress their inner speech (and indeed
all conscious thought) through varieties of meditation.
One thing we can be sure about is that
inner speech takes many forms. Some will be good for explicit
self-regulation and motivation; others will be closer to a kind of deep
thinking with no particular sound quality. In fact, understanding inner
speech better will help us to be clearer about what we mean by the
nebulous term "thinking", and in this way make progress with some
long-standing philosophical problems about how language, cognition and consciousness work together.
When I think about my own inner
speech, I keep coming back to Vygotsky's ideas about "condensation".
Sometimes I catch myself in the middle of a full-blown argument with
myself, debating things from different points of view. Most of the time,
though, the experience is more fragmentary: thoughts and feelings that
are close to being put into language, but are not yet quite the kind of
speech you would hear spoken out loud. Vygotsky likened this transition
of thought into speech to "a cloud shedding a shower of words".
Condensed or expanded, this rich internal dialogue must hold clues to
understanding the distinctively creative, flexible properties of human
thought.
This article appeared in print under the headline "Life in the chatter box"
Bibliography
- Links to the relevant papers can be found in the online version of this article
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