Origins of Language by Hurford James R

Author:Hurford, James R.
Language: eng
Format: epub, pdf
Publisher: OUP Oxford
Published: 2014-09-09T16:00:00+00:00

Questions about hearing speech

Humans have complementary abilities to produce and to perceive and interpret speech sounds. Today in communication these abilities work together. The range of sounds that we produce with our mouths and throats for communicative speech lies within the range of sounds that the human ear can detect. (Otherwise, what would be the use of speaking?) Speech and human hearing appear ‘made for each other’. The evolutionary question that arises is: ‘Which adapted to which?’ During our evolution, did vocal tracts change their shape, and did the controlling motor mechanisms change, so that the sounds they could produce were specially fitted to what the pre-existing human ear could detect and disentangle into meaningful messages? This would be a one-way process of speech production adapting to our hearing, without the hearing itself becoming more specialized. The reverse one-way possibility is that human hearing adapted specifically to detect and interpret a new class of sounds—those which happened to be makeable by our vocal tracts as they already were. It’s clear that speech sounds are not the only sounds we can hear. We (fortunately) can hear non-speech sounds, like rushing wind, footsteps, and thunder, but only a few gifted entertainers can make sounds approaching these with their vocal tracts. So on the face of things, it would appear that human hearing is general purpose, and not specifically adapted to speech.

These two hypothetical alternative one-way adaptive stories—either speech adapted to hearing or human hearing adapted to speech—are simple. A more complex story is that speech and human hearing co-evolved to some extent. Co-evolution of coordinating systems is common in complex organisms. In a co-evolutionary story about speech, human hearing, though admittedly versatile, has nevertheless become at least somewhat specialized for speech, and speech production has also evolved in ways specially suited to human hearing. In the previous two sections, we looked at our speech organs themselves, and the motor abilities for using them, with a view to tracing their evolutionary history. Now we’ll consider the extent to which human hearing is special, compared to that of other animals.

When a normal adult human hears speech, a train of events occurs, penetrating further and further into the head from the outside. The early processes are mechanical, and the later processes are neurological or ‘electrical’. The mechanical processes are sensory, from vibrations picked up at the eardrum to the twitching of little hairs in the cochlea of the inner ear. After that, the processes are perceptual, a matter of how the brain interprets the information delivered to it by the sensory system. Without sensation, there can be no perception. If certain key properties of a stimulus cannot be sensed, perception is hampered in analysing it. But often, with complex stimuli as occur in nature, perception is robust enough to work around the lack of some input from the sensory system and successfully recognize a stimulus. Expectations due to context help. This makes it difficult to distinguish experimentally with realistic stimuli between an animal’s raw sensory acuity and its perceptual abilities.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.