The science of how we talk to ourselves in our heads

Studying the ways people talk to themselves in their own minds is incredibly tricky because as soon as you ask them about it, you're likely interfering with the process you want to investigate. As William James said, some forms of introspective analysis are like "…trying to turn up the gas quickly enough to see how the darkness looks."

For many years Russell Hurlbert and his colleagues have used a technique that they believe offers the best way to study what they call "pristine" inner speaking, unaltered by outside interference. They provide participants with a beeper that goes off randomly several times a day, and ask them to record in precise terms their mental activity that was happening just before the beeps. Early in the process, this "descriptive experience sampling" (DES) approach also involves cooperative interviews between the participants and a trained researcher, so that the participant can learn to identify true instances of inner speaking from other mental phenomena.

Now Hurlbert's team has documented some of what they've learned so far about the ways that we talk to ourselves in our own minds. Our inner voices usually sound to us like our external spoken voice – instances of inner speaking occurring in another person's voice are very rare. Just like our spoken voice, the voice of inner speaking can also express degrees of volume and emotion.

Inner speaking is perceived as wilful – something done, rather than experienced passively. There is huge variation in the frequency with which people speak to themselves in their mind. In one study with 30 participants that involved ten beeps a day for three days, some reported no instances of inner speaking at all, while others reported inner speaking for 75 per cent of the beeps. On average inner speaking was reported at 23 per cent of beeps, although note that doesn't mean people are speaking to themselves 23 per cent of the entire time.

Another curious variation in inner speaking is where people report its location. Some people describe it as occurring in a particular location in their head; others say in their head but are no more specific; still others say their inner speaking occurs in their chest.

Also notable is some people's descriptions of inner speaking occurring while they are speaking aloud – with the two voices saying different things. There are also reports of inner speaking that has no meaning, and inner speaking that is at a much faster rate than would be physically possible for aloud speaking.

Hurlbert's team say it is also important to outline what inner speaking is not. They say it is different from "inner hearing," which is when an inner voice is experienced passively, even if it is one's own voice. This can give rise to a situation where a person has an inner discussion between their inner speaking voice and their heard voice. The researchers give this example from their records, of a man eating dinner in a restaurant, who then notices a woman:

Innerly speaking voice: Why are you bringing this woman to my attention?

Innerly heard voice: She's pretty (spoken in a matter of fact tone).

Innerly speaking voice: Uh huh ("in a that's-bullshit tone of voice")

[Beeper goes off]

Inner speaking is also different from "unsymbolised thinking" according to the researchers. Unsymbolised thinking is a "thoughty experience" about a distinct concept or issue but does not involve words, pictures or symbols. Inner speaking also is not "sensory awareness" – when we're focused on a specific sensory aspect of the outside world or our bodies.

Hurlbert's group believe their approach has advantages over the questionnaire methods used by other researchers, which obviously rely on people remembering their past mental lives, and are often vague in what they mean by inner speaking. And Hurlbert's group think their method is more trustworthy than simple armchair introspection, because if you sit back and deliberately attempt to analyse your own inner speaking you will immediately interfere with the natural course of your mental activities.

They conclude by outlining many puzzles that remain to be investigated, including why some people appear to experience so much more inner speaking than others (some people report that they experience inner speaking 100 per cent of the time, yet others report none). Also, are there cross-cultural differences in inner speaking? And when and how does inner speaking first appear in life?

Further reading

Hurlburt RT, Heavey CL, and Kelsey JM (2013). Toward a phenomenology of inner speaking. Consciousness and cognition, 22 (4), 1477-94 PMID: 24184987