PRIMARY hearing is what alerts us, gives us the sense of direction and the notions of distances and volumes. All this, really ?? The primary function of the ear « … is to perceive our environment »(1).
Let us start with direction.
……….1) ALERT/DIRECTION :
Any sudden variation of the sound level in our surroundings systematically makes us turn over and look at where this variation comes from.
We pay attention to this alert, instinctively.
The neural pathway gives priority to the event that triggers this variation of sound level. Alertness is at its peak level, as there may be critical danger.
This reflex, which consists in turning towards the sound source, is a behavioural observation response and originates from the fact that, as a new-born, we feel our mother’s breast and turn to it to be fed.
« Any change in our surroundings, any emerging signal of different intensity (impulse) or shape, of unusual or conditioned nature, triggers a subconscious alert mechanism that results in acute attention and in the investigation of the signification of the potential danger arising from what became a signal »(2).
This instinctive reaction allows us to identify where the signal comes from.
Two other major mechanisms are involved. These allow us in particular to make a selection based on the signal we perceived : this is either a signal of interest and we process it further, or this is an irrelevant signal and we discard it. These mechanisms either enhance excitation or annihilate it.
Giving up on irrelevant excitation (like the noise of an air-con above our head, or a train passing by daily at the same time) is the habituation mechanism.
Enhancing this sound excitation (like a baby crying in the bedroom while we are chatting with friends in the living room) is the facilitation mechanism.
« Both mechanisms set up the basis of social life »(3).
In a nutshell, the alert signal provides the direction.
« Sadly, deaf children are inherently « accustomed » not to get alerted by sounds they do not perceive. They do not possess this function of acoustic alarm signal and they have to use their vision instead, which is less global. Indeed, deaf children use their sight to explore their surroundings and to detect any potential change, they are thus forced to remain vigilant due to a lack of permanent alerting system. As a result, they are often distracted and have more trouble to fix their attention for extended periods of time. They need comforting surroundings, someone to rely on to give the alert, and a stable, predictable environment in order to focus on what they do »(2).
Deaf children thus often have a tendency to stay back, unlike those wearing hearing aids. Providing these children with hearing devices allows them to open naturally to their environment, juste like people who can hear normally.
(1) Professor J.C. LAFON « hearing-impaired children » page 19.
(2) Professor J.C. LAFON « hearing-impaired children » page 101.
(3) Professor J.C. LAFON « message and phonetics » page 66.
(translated from french by O.B.)