Motor Overflow

Many of us—children more than adults, but adults do this, too—subconsciously stick out our tongues when we're concentrating mightily on some kind of manual task.

This is thought (according to one theory, at least) to be the consequence of what's called "motor overflow," which refers to a connection between our motor skills (handling tools, weaving, juggling) and our linguistic capabilities (using our mouths and tongues and larynxes to communicate).

The general idea is that the portions of our brains that manage physical dexterity are interwoven with neighboring regions that guide our vocal apparatuses, which at times can lead to unintentional, subconscious movement in one area when we're tightly focused on the other.

The "tongue sticking out" response is especially prominent when we're focused on utilizing finger-heavy motor skills, as our fingers and tongues are the only fine articulators (ultra-controllable digits and muscles) in the human body, and what we know about how the brain orchestrates the use of these bodily components highlights all sorts of connections between them.

Those connections imply an evolutionary relationship between our capacity to engage in demanding, manually dexterous work, and the incredibly refined use of our tongues that allows us to form an array of vowel and consonant sounds.

Research has shown other connections between these capabilities, too, ranging from our tendency to use our hands as part of spoken communication, to a baby's seeming inability to explore the world with just their fingers or mouths—using hands and tongues in almost undifferentiated ways to explore the world around them.

Other studies have tracked movement in unused hands when just one hand is involved in some kind of focused, manual activity, and still others suggest that our grip precision and strength can be influenced by our simultaneous pronunciation of certain sounds (which requires we move our tongues in specific, neuron-aligned ways, and provides us with rationales for why some martial artists shout particular sounds when executing thrusts, and why many tennis players do the same when performing a powerful serve).

All of which is interesting because of what it suggests about how language may have evolved in our ancestors, alongside our capacity for increasingly sophisticated and controlled hand- and finger-use.

But this theory is also potentially helpful for increasing our understanding of brain structure and development, especially in infants, and especially in folks who suffer from a range of physical or psychological ailments that may be at least partially addressed by looking more closely at these relationships.