Humans are social creatures by nature – we are made to interact with family, neighbours and friends. Modern advances in social media notwithstanding, that interaction is best accomplished in person, using the senses of sound, sight and touch.

Despite the fact that many people would name sight as their primary sense, and the fact that it is undoubtedly important for human communications, it is our sense of hearing that we rely upon most for social interaction. Most of us need to talk to people face-to-face to really communicate, and most of us find it to be a much more efficient communications mechanism than writing, as well as being more personal. Readers who prefer email to telephone (as does the author) might also realise that their preference stems in part from being better able to regulate or control the flow of information. In fact this is a tacit agreement that verbal communications can allow a higher rate of information flow, so much so that they (we) prefer to restrict or at least manage that flow.

Human speech and hearing are also very well matched: the frequency and amplitude range of normal human speech lies well within the capabilities of our hearing system. While the hearing system has other uses apart from just listening to speech, the output of the human sound production system is very much designed to be heard by other humans. It is therefore a more specialised subsystem than is hearing. However, despite the frequency and amplitude range of speech being much smaller than our hearing system is capable of, and the precision of the speech system being lower, the symbolic nature of language and communications layers a tremendous amount of complexity on top of that limited and imperfect auditory output. To describe this another way, the human sound production mechanism is quite complex, but the speech communications system is massively more so. The difference is that the sound production mechanism is mainly handled as a motor (movement) task by the brain, whereas speech is handled at a higher conceptual level, which ties closely with our thoughts. Perhaps that also goes some way towards explaining why thoughts can sometimes be ‘heard’ as a voice or voices inside our heads?