Talkin’ 2 Myself: Eminem and the Science of Inner Speech

The other day, I was listening to Eminem’s “Talkin’ 2 Myself,” and I started thinking about the therapeutic effects of talking to oneself (coincidentally, Eminem briefly discussed the song with Big Boy on Power 106 this Monday!   Seriously random, considering Recovery was released in 2010…).  Specifically, I was curious about the fine line between working out your problems in your head (so, like Eminem, you can avoid saying an unnecessarily mean comment about Lil Wayne) and rumination, which is what happens when a cow chews regurgitated food…

As my thoughts wandered, I began to ask myself more questions about inner speech.  Does everyone talk to themselves this much?  How much is this much?  Am I always talking to myself but am ignoring my inner speech the way my friends ignore my outer speech?  Is this healthy?  What’s the difference between thinking about possible or past conversations (when I have the potential to be so witty and charming) and this excessive string of thoughts that are meant only for myself (except for when I blog about them later)?  How do deaf people talk to themselves?  Does my dog talk to herself?  She is deaf and also a dog.  Is it considered inner speech when I think of something that I cannot quite put into words?  Is it still considered inner speech when I am reading someone else’s words?  Oops, I accidentally just moved my lips—does that still count as inner speech?  And then I attempted to quiet my inner voice, and fell into an infinite loop of Be quiet – Who said that? – Dangit!  And then I decided to take these questions out of my brain and ask science.  Thankfully, my search for the answers to all my questions assured me that I am not the only one who is mystified by inner speech.

This is my brain on thoughts. (From here)

According to a series of studies that use beepers to track the “inner experiences” of participants, approximately one quarter of our conscious, awake life consists of inner speech1.  In these studies, participants are beeped approximately 6 times a day and must report all immediate “inner experiences” at the moment of the beep.  In addition to inner speech, these experiences can include  “inner hearing” of music, awareness of sensory perception, or wordless wondering, which may be considered inner speech by others (discussed below).  The experimental design, called “Descriptive Experience Sampling,” requires a lot of time and practice from the participants and interviewers.  If you’d like to try it yourself, you can use the smart phone app iPromptU!  Anyway, the overall conclusion from these studies on multiple populations is that  inner speech varies greatly between individuals–some participants are never engaged in inner speech when they are beeped, but others always seem to be talking to themselves.  That would be me.  Phew!

What is inner speech? 

Inner speech has many names and manifestations.  For example, I could talk about inner voice, self-talk, verbal thoughts, inner rehearsal, internal monologue, internal dialogue, phonological loop, and silent verbalizations.  This makes for a very tedious date with Google and PubMed.

My favorite conception of inner speech comes from Dr. Charles Fernyhough2, who partitioned the development of inner speech into four levels.  As we develop, we move from level 1 to level 4 and then jump around between levels, depending on the situation:

  1. External Dialogue: because you can’t just keep it to yourself
  2. Private Speech: subvocalized dialogue
  3. Expanded Inner Speech: fully internalized but with dialogic qualities (i.e., it “sounds” like you’re actually talking)
  4. Condensed Inner Speech: an abbreviated, abstract dialogue, or to quote the incredible Lev Vygotsky,  “thinking in pure meaning” (i.e., when you can’t put your thoughts into words but you can still “hear” them)

But what is inner speech?

Okay, so having a ton of theoretical definitions makes inner speech difficult to study in practice.  For now, let’s stop at expanded inner speech, which “sounds” like real speech.  (This will avoid confusing findings like infants using inner speech even though they can’t talk3 and stutterers with 100% fluent inner speech4).  One of the major theories is that this inner speech is basically overt (out loud) speech in which motor execution is blocked before sound is produced.  This is supported by several findings that language areas in the left hemisphere (such as Broca’s and Wernicke’s areas and the inferior parietal lobule) are activated in both inner and overt speech, while activation of the motor cortices is decreased for inner speech4.  There is differential activation in many other areas, possibly due to the lack of head motion or active motor suppression during inner speech.  So the neural correlates of expanded inner speech are partially but not completely overlapping with those involved in overt speech, and we’re still not sure why.

Here’s a cute picture highlighting some of the important speech areas.  From Wikimedia Commons and modified by Dr. C. George Boeree.

Silent reading is different from expanded inner speech, and the areas involved are more closely linked to those involved in speech perception, rather than speech production.  Silent reading of quotations activates the temporal voice areas of the auditory cortex, which are necessary for voice perception5. (I wonder if the brain responds differently to quotations that are indicated with quotation marks, italics, or not at all.  The “godfather of creative nonfiction,” Lee Gutkind, says that nonfiction writers use the latter methods to give themselves a little leeway, just in case they aren’t sure they’re remembering quotes correctly.  Are they taking advantage of the neural system here?).  Besides the quotations and the voice that we give to the narrator, there are other percepts that come to mind while reading.  Perrone-Bertolotti et al. (2014) summarized this in a sentence that I had to re-read twice with lip movements:  “…the rich and seemingly coherent audiovisual experience of reading arises from a heterogeneous amalgam of asynchronous neural responses.”  In other words (I think), even though it seems like one smooth process, a whole lot of stuff is happening in a bunch of areas of our brains when we read, and we shouldn’t take that for granted!!

The temporal voice-selective areas are along the top of the superior temporal sulcus (red).

My perusal of the literature indicates that all we know about the localization of condensed or abstract inner speech (aka “verbal mind wandering”) is that it involves the default mode network5, which is active when the brain is at rest.  This information is not terribly useful for determining which specific areas are important for this type of inner speech, but maybe a comparison between those who never engage in inner speech and those who constantly engage in inner speech might be enlightening?

Mmmm… default.

How do deaf people talk to themselves?

Internal representation of signs!  The descriptions of inner signing are more similar to abstract inner speech than to “seeing” signs.  Interestingly, inner signing involves the left inferior frontal cortex that is involved in inner speech and not the visuo-spatial areas that you might expect due to the visual nature of signing.  This probably reflects the fact that signs are not just gestures to look at… just like spoken words, they convey meaning!  This is supported by reports that some deaf people have experienced auditory verbal hallucinations7.  Due to the subjective nature of these accounts, it is impossible to tell what exactly these experiences are like, but it is likely that what is “heard” is a command or message that does not require a sensory modality to be understood.   (Where, then, does that leave imagined or remembered mental images?  Could they be categorized as abstract inner speech?  I haven’t gotten that far in the literature yet..)

This sick image is from a talk that I would’ve liked to attend at NYU.

When is inner speech good and when do I need to shut it down?

Several studies (and personal anecdotes) have shown that inner speech is helpful when switching between tasks and holding information in working memory4.  You’d probably guess that expanded inner speech is helpful for problem solving (don’t tell me you were able to get to 2048 without talking to yourself), but mind-wandering also helps with problem solving8.  Paradoxically, in certain tasks that require your attention (e.g., watch the screen and report when you see an image), letting part of your mind wander to task-irrelevant thoughts makes it easier to pay attention to the primary task9.  (This reminds me of the relief I felt when I read that doodling in class is a good thing).  Inner speech may in fact have been evolutionarily necessary for the development of learning and reasoning10.

Unfortunately, inner speech can get out of hand.  Mental rumination is repetitive, compulsive inner speech that is focused on negative feelings, memories, and anxieties.  Rumination is considered a dysfunction of inner speech and is a symptom of depression.  Depressed and dysphoric patients often suffer from rumination and concurrent cognitive decline11.  As a former non-cow ruminator, I highly recommend asking your doctor if your thoughts are getting in the way of your work!  Shut that negative inner speech down! 

What about that other voice inside my head?

If the voice inside your head actually sounds like it is coming from someone else, you most definitely want to have that checked out (unless you are Marshall Mathers hearing Slim Shady’s voice?  But multiple personalities are a whole other disorder).  There are many theories for the generation of auditory verbal hallucinations (AVH), which are common in patients with schizophrenia (this interview with artist Sue Morgan about some of her hallucinations was uploaded by Nature yesterday, and I highly recommend that you check it out).  A popular theory (that I researched for my “minor prop” and wrote about here), is that AVH occurs when a person does not realize that he or she has produced the thought he or she “hears.”  This can happen due to a faulty feed-forward network that should quiet the auditory cortex (i.e., your motor neurons telling your auditory cortex that the incoming “sounds” are self-generated, so it doesn’t get too excited).  This confusion might also arise if there is a time lapse between the perception of the motor command and the perceived thought, so the thinker/listener cannot attribute the input to his or her own mental output12,13,14.  Alternatively, AVH might also be the result of misplaced/misunderstood auditory memories15.  Who knows?

The above are just a handful of inner-speech-related questions.  I hope they made for some interesting inner speech while you were reading and will continue to visit your wandering mind as you consider our future conversations!

 

References: 

1.        Hurlburt, R. T., Heavey, C. L. & Kelsey, J. M. Toward a phenomenology of inner speaking. Conscious. Cogn. 22, 1477–94 (2013).

2.        Fernyhough, C. Alien voices and inner dialogue: towards a developmental account of auditory verbal hallucinations. New Ideas Psychol. 22, 49–68 (2004).

3.        Mani, N. & Plunkett, K. In the infant’s mind’s ear: evidence for implicit naming in 18-month-olds. Psychol. Sci. 21, 908–13 (2010).

4.        Perrone-Bertolotti, M., Rapin, L., Lachaux, J.-P., Baciu, M. & Lœvenbruck, H. What is that little voice inside my head? Inner speech phenomenology, its role in cognitive performance, and its relation to self-monitoring. Behav. Brain Res. 261, 220–39 (2014).

5.        Belin, P., Zatorre, R. J., Lafaille, P., Ahad, P. & Pike, B. Voice-selective areas in human auditory cortex. Nature 403, 309–12 (2000).

6.        Alexander, J. D. & Nygaard, L. C. Reading voices and hearing text: talker-specific auditory imagery in reading. J. Exp. Psychol. Hum. Percept. Perform. 34, 446–59 (2008).

7.        Atkinson, J. R. The perceptual characteristics of voice-hallucinations in deaf people: insights into the nature of subvocal thought and sensory feedback loops. Schizophr. Bull. 32, 701–8 (2006).

8.        Baars, B. J. Spontaneous repetitive thoughts can be adaptive: postscript on “mind wandering”. Psychol. Bull. 136, 208–10 (2010).

9.        Olivers, C. N. L. & Nieuwenhuis, S. The beneficial effects of additional task load, positive affect, and instruction on the attentional blink. J. Exp. Psychol. Hum. Percept. Perform. 32, 364–79 (2006).

10.     Agnati, L. F. et al. Possible genetic and epigenetic links between human inner speech, schizophrenia and altruism. Brain Res. 1476, 38–57 (2012).

11.     Davis, R. N. & Nolen-hoeksema, S. Cognitive Inflexibility Among Ruminators and Nonruminators. 24, 699–711 (2000).

12.     McGuire, P., David, A. & Murray, R. Abnormal monitoring of inner speech: a physiological basis for auditory hallucinations. Lancet 0–4 (1995).

13.     Blakemore, S. J., Smith, J., Steel, R., Johnstone, C. E. & Frith, C. D. The perception of self-produced sensory stimuli in patients with auditory hallucinations and passivity experiences: evidence for a breakdown in self-monitoring. Psychol. Med. 30, 1131–9 (2000).

14.     Curcic-Blake, B. et al. When Broca goes uninformed: reduced information flow to Broca’s area in schizophrenia patients with auditory hallucinations. Schizophr. Bull. 39, 1087–95 (2013).

15.     Waters, F., Badcock, J. C., Michie, P. T. & Maybery, M. T. Auditory hallucinations in schizophrenia: intrusive thoughts and forgotten memories. Cogn. Neuropsychiatry 11, 65–83 (2006).

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