Clearly, this is because the entire purpose of talking aloud is to communicate with others. But given that so many of us do talk to ourselves, could it be normal after all -- or perhaps even healthy?
We actually talk to ourselves silently all the time. I don't just mean the odd "where are my keys?" comment -- we actually often engage in deep, transcendental conversations at 3am with nobody else but our own thoughts to answer back.
This inner talk is very healthy indeed, having a special role in keeping our minds fit. It helps us organise our thoughts, plan actions, consolidate memory and modulate emotions. In other words, it helps us control ourselves
Talking out loud can be an extension of this silent inner talk, caused when a certain motor command is triggered involuntarily. The Swiss psychologist Jean Piaget observed that toddlers begin to control their actions as soon as they start developing language
. When approaching a hot surface, the toddler will typically say "hot, hot" out loud and move away. This kind of behaviour can continue into adulthood.
Non-human primates obviously don't talk to themselves but have been found to control their actions by activating goals in a type of memory that is specific to the task
. If the task is visual, such as matching bananas, a monkey activates a different area of the prefrontal cortex than when matching voices in an auditory task.
But when humans are tested in a similar manner, they seem to activate the same areas regardless of the type of task.
In a fascinating study
, researchers found that our brains can operate much like those of monkeys if we just stop talking to ourselves -- whether it is silently or out loud.
In the experiment, the researchers asked participants to repeat meaningless sounds out loud ("blah-blah-blah") while performing visual and sound tasks. Because we cannot say two things at the same time, muttering these sounds made participants unable to tell themselves what to do in each task. Under these circumstances, humans behaved like monkeys do, activating separate visual and sound areas of the brain for each task.
This study elegantly showed that talking to ourselves is probably not the only way to control our behaviour, but it is the one that we prefer and use by default. But this doesn't mean that we can always control what we say.
Indeed, there are many situations in which our inner talk can become problematic. When talking to ourselves at 3am, we typically really try to stop thinking so we can go back to sleep. But telling yourself not to think only sends your mind wandering, activating all kinds of thoughts -- including inner talk -- in an almost random way.
This kind of mental activation is very difficult to control, but seems to be suppressed when we focus on something with a purpose. Reading a book, for example, should be able to suppress inner talk in a quite efficient way, making it a favourite activity to relax our minds before falling asleep.
But researchers have found that patients suffering from anxiety or depression activate these "random" thoughts
even when they are trying to perform some unrelated task. Our mental health seems to depend on both our ability to activate thoughts relevant to the current task and to suppress the irrelevant ones -- mental noise.
Not surprisingly, several clinical techniques, such as mindfulness, aim to declutter the mind and reduce stress
. When mind wandering becomes completely out of control, we enter a dreamlike state displaying incoherent and context-inappropriate talk that could be described as mental illness.
Loud vs silent chat
So your inner talk helps to organise your thoughts and flexibly adapt them to changing demands, but is there anything special about talking out loud? Why not just keep it to yourself, if there is nobody else to hear your words?
In a recent experiment in our laboratory at Bangor University, Alexander Kirkham and I demonstrated that talking out loud actually improves control over a task
, above and beyond what is achieved by inner speech.
We gave 28 participants a set of written instructions, and asked to read them either silently or out loud. We measured participants' concentration and performance on the tasks, and both were improved when task instructions had been read aloud.
Much of this benefit appears to come from simply hearing oneself, as auditory commands seem to be better controllers of behaviour than written ones. Our results demonstrated that, even if we talk to ourselves to gain control during challenging tasks, performance substantially improves when we do it out loud.
This can probably help explain why so many sports professionals, such as tennis players, frequently talk to themselves during competitions
, often at crucial points in a game, saying things like "Come on!" to help them stay focused. Our ability to generate explicit self instructions is actually one of the best tools we have for cognitive control, and it simply works better when said aloud.
So there you have it. Talking out loud, when the mind is not wandering, could actually be a sign of high cognitive functioning. Rather than being mentally ill, it can make you intellectually more competent.
The stereotype of the mad scientist talking to themselves, lost in their own inner world, might reflect the reality of a genius who uses all the means at their disposal to increase their brain power.