Why Inner Speech?
Michael Johnson
VAP Lingnan University (HK)
Outline
1.
2.
3.
4.
What Is Inner Speech?
Why Inner Speech?
Inner Speech and Attention
Conclusion
1. WHAT IS INNER SPEECH?
Inner Speech
As I’ll use the term, “inner speech” is a label for
the phenomenon we naturally describe as
“thinking in English/ Cantonese/ Catalan/
Kalaallisut/ etc.”
But what is the nature of this phenomenon and
how is it related to thought and “outer” speech?
Arguments that LOT ≠ English
Extensional inequivalence:
• Pre-linguistic infants think (else they can’t
learn languages).
• Deaf adult humans who don’t know signlanguage (or a spoken language) think.
• Non-human animals think.
Arguments that LOT ≠ English
Greater indeterminacy of English compared with
LOT:
• Lexical ambiguity: “Fred went to the bank.”
• Structural ambiguity: “Flying planes can be
dangerous.”
• Scopal ambiguity: “Every boy loves some girl.”
Processes Implicated in Speech
• Lexical selection: selecting lexical items
• Syntactic encoding: arranging the lexemes
according to the syntactic rules
• Phonological code retrieval [encoding]:
retrieving [producing] phonological
information
• Phonetic encoding: Putting the information
into an articulatory code
• Articulation
Lexical Selection: Left Middle Temporal
Gyrus, Mid Section
Syntactic Encoding: Left Inferior
Frontal Gyrus/ Broca’s Area
Syntactic Encoding: Middle Frontal
Gyri
Syntactic Encoding: Superior Parietal
Lobule
Phonological Code Retrieval: Right
Supplementary Motor Area
Phonological Code Retrieval: Left
Anterior Insula
Phonological Code Retrieval:
Wernicke’s Area
Phonological Encoding: Broca’s Area
Phonological Encoding: Left MidSuperior Temporal Gyrus
The Brain and Inner Speech
Importantly, in both inner speech and auditory
visual imagery (imagining someone else saying
something), all these brain areas are active.
Many researchers (e.g. Bookheimer 2002) think
the brain activity in inner speech is the same as
in overt speech– just a little less strong, and
minus phonetic encoding and articulation.
Broca’s Area
Finally, patients with damage to Broca’s area can
suffer expressive aphasia– an inability to speak
or write words.
Transcranial magnetic stimulation of Broca’s
area has been shown to inhibit inner speech
(Aziz-Zadeh, Cattaneo, Rochat & Rizzolatti, 2005)
The Phenomenal Character of IS
Inner speech is an auditory phenomenon.
• The phrase “hear myself think” gets 1.4m
google hits compared with 640,000 for “feel
myself think.”
• Interestingly, BA 41/42 (the auditory cortex) is
not (to my knowledge) activated in inner
speech. The auditory cortex contains the
neural correlates of auditory consciousness.
Summary
• Inner speech is distinct from thought.
• Inner speech involves all of the brain areas
used in encoding thought into language
except the areas involved in phonetic
encoding and articulation.
• Inner speech is an auditory phenomenon(?)
General Model
Thought
↓
Linguistic encoding (LE) of thought
↓
LE sent to speech production apparatus = outer
speech
General Model
Thought
↓
Linguistic encoding (LE) of thought
↓
LE sent to auditory mechanism = inner speech
2. WHY INNER SPEECH?
“What good could talking to yourself do,
if you already knew what you intended
to say?” Dennett (1991 p. 301)
The Basic Puzzle
Suppose I have a thought. If I don’t plan on
communicating it to anyone in the foreseeable
future, why would I:
• Find the words that express the components
of the thought;
• Arrange them according to the rules of
grammar;
• Figure out how they would sound;
• And then “listen” to them?
Some Solutions I Don’t Like
• There’s no reason why we engage in inner
speech. Only a befuddled hyper-adaptationist
would think there had to be a reason.
• The reason has nothing to do with inner
speech: inner speech is a side-effect.
• Inner speech is conscious whereas our
“unspoken” thoughts aren’t: inner speech
allows us to “globally broadcast” information.
No Function?
The burden of proof is always on the side that
wants to claim that a cognitive feature is
adaptive and does have a function.
That being said, there’s plenty of evidence that
deficits in inner speech (either temporary or
permanent) result in severe cognitive
impairment.
Benefits of Inner Speech
Here are just some of the areas impaired by a
deficit in inner speech:
•
•
•
•
self-awareness
intelligence
mathematical ability
memory
Side-Effect Story
For fully verbalized outer speech, it is necessary
to encode our thoughts in language, and to do
so very rapidly.
Ideally, we would perform this encoding only
when necessary, but nature is rarely ideal.
Instead we perform the encoding even in those
large number of instances where we have no
plans to engage in verbal behavior.
Problems for Side-Effect Story
1. The story doesn’t explain how inner speech
conveys the benefits to intelligence, memory,
etc.
2. There’s an extra step in inner speech that’s
not needed in “outer” speech: routing the
phonological representations to the auditory
cortex.
“Global Broadcast” Story
Carruthers suggests that inner speech exists as a
medium for the different modules to “talk to”
one another.
This seems implausible. How could something
linguistically encoded in principle be globally
accessible? Just how many mental faculties can
process language?
Here’s the Story I Like
A salient difference between thought and
audition is that the former is essentially nonperceptual and the latter is essentially
perceptual. As we’ll see, that makes quite a
difference.
3. INNER SPEECH AND ATTENTION
In the rest of the talk, I want to try to outline
how it is that inner speech is involved in what
research says it’s involved in:
•
•
•
•
Memory
Mathematical Ability
Self-Awareness
Intelligence
Attention
Attention involves selecting an aspect of our
perceptions (or our sensations) and allocating
additional cognitive resources to that aspect.
Attention can thus only be provided to and
withheld from perceptions and sensations.
Short-Term Memory
Knudsen (2007) sees attention as the means by
which information enters short-term memory.
Thus for information to enter short-term
memory, it must come to us through sensation
or perception.
Inner Speech and Memory
Inner speech, as I’ve argued, is an auditory
phenomenon. Thus it, unlike ordinary thought*,
is precisely the sort of thing we can attend to.
Unsurprisingly, research has shown that inner
speech aids in memory (Baddely 1986).
Memory
• Mathematical Ability
• Self-Awareness
• Intelligence
Memory and Mathematics
Performing all but the simplest arithmetical
calculations requires storing the values of
intermediate calculations in short term memory.
If attention is essentially perceptual, and is also
the gateway to short-term memory, then a
perceptual presentation of arithmetical
problems is necessary for solving them.
Inner Speech and Arithmetic
This presentation can be visual (on a chalkboard,
for example), but it can also be auditory.
Research reveals that private speech increases
arithmetical ability in children (Ostad &
Sorensen 2007) and that one of the cognitive
deficits that faces deaf individuals who have
learned no language is poor arithmetical ability.
Memory
Mathematical Ability
• Self-Awareness
• Intelligence
Self-Awareness
Self-awareness is “the capacity to become the
object of one’s own attention (Duval and
Wicklund, 1972), where the individual actively
identifies, processes, and stores information
about the self… Self-awareness involves
attention paid to one’s own mental states (such
as perceptions, sensations, attitudes, intentions,
emotions, etc.) and public self-characteristics.”
[Morin 2005, emphasis mine]
Self-Awareness and Inner Speech
“[T]hrough a process of labeling, categorizing,
and engaging in language-based modes of
representation, a person not only represents
internal states and experiences (sentience) but
acquires the capacity to reflect on them. [Burns
& Engdahl 1998: 179]
“Without language [internal monitoring
remains] relatively primitive, vague,
unelaborated.” [171]
Self-Awareness and Inner Speech
Here’s the basic picture:
Awareness of our own thoughts is difficult to
come by.
The best way to get it is to translate the thought
into language, then “speak” it to ourselves.
This allows us to attend to the thought and
discover what we are thinking.
Memory
Mathematical Ability
Self-Awareness
• Intelligence
Why We Are So Clever
“[A] creature that knows
what would make its
thoughts true and what
would cause it to have
them, would be in a highly
advantageous epistemic
position:…”
Why We Are So Clever
“It would be able, with premeditation, to cause
itself to have true thoughts. In particular, to
construct, with malice aforethought, situations
in which it will be caused to have the thought
that P if and only if the thought that P is true.”
Why We Are So Clever
“I think it's likely that we
are the only creatures that
can think about the
contents of our thoughts.”
Memory
Mathematical Ability
Self-Awareness
Intelligence
4. CONCLUSION
Summary of the Talk
Part 1: Inner speech is speech that is not
articulated. It is not thought itself, but thought
encoded linguistically.
Part 2: A puzzle arises as to how encoding our
thoughts in a linguistic medium conveys any
benefit to us.
Summary of the Talk
Part 3: The puzzle is resolved when we notice that
attention is fundamentally sensory/ perceptual.
We can attend to LEs in a way that we can’t attend
to thoughts. This allows us to store intermediate
calculations so encoded in short term memory, and
also allows us to become self-aware of our
thoughts.
This self-awareness is the fountainhead of human
intelligence.
Thank You!