Auditory Object Perception (AOP) is the utilization of the presence or absence of reflected sound, which assists the blind person in locating objects before physical contact (in his/her own path and to the side) and orienting to a space by being able to detect objects in that space. A high frequency sound is produced, so that when an object is approached, the reflected sound may be heard. When receding from an object, the frequency is lower. The magnitude depends upon the velocity of the sound waves, the movement of the person, etc. The sound heard is described as a "closeness," "pressure," "shadow," or "tunnel" and can be thought of as the "sea shell effect." In the literature, this is known as "echolocation."
The state-of-the-art regarding research into the early movement of blind children and how they come to know their world is summarized by Dodson-Burke, Hili, and Smith (REVIEW, Summer 89). They state: "For children two years of age, familiarity with and knowledge of the structure of external space may be largely dependent upon movement within that space." There is virtually no research that links the quality of movement to the degree to which children two years old and younger are familiar with their environments.
My own experience with young blind children and how they express AOP tells me that it does indeed increase the quality of movement and orientation during this earlyunder two years of agesensorimotor stage of development by enabling the child to search out and explore the world (via sound space exploration) in a more efficient and meaningful manner. These children develop more autonomy, postural security, and knowledge of the object world.
The 0&M specialist can introduceto parents and early intervention staffthe concept of affordance regarding appropriate toys for play. Holly Ruff states that "... the structure and function of an object are critical to its recognition." The more the object affords the child, the more invitation the child has to explore. For example, playing with different size containers (plastic, metal, cardboard, etc.), dropping objects into them, holding them up by the child's ear, etc....all of these activities introduce the blind baby to the "amusement of the sound space world."
In the early years, parents are attaching to their baby through touch affections. Blind babies will give meaning to sounds through these pleasurable and secure touch feelings. The match and expectation of loving touch and human sounds becomes anticipated. The face-to-face exploration and closeness of parents and baby assist in the rudimentary development of object permanencethe precursor being person permanence. Walter Ong writes: "Touch attests to the objective reality in sense of something outside myself, and yet the very fact it attests the not-me more than any other sense, touch involves my own subjectivity more than any other sense."
AOP expresses itself more obviously during the locomotion of very young blind children, specifically around the event of crawling. This skill is used for self-protection and a more efficient movement in space, as well as learning to know the arrangement of the world. (Auditory reach is the hallmark of object permanence in the blind baby. Auditory reach will be the precursor to AOP as more subtle sounds are discriminated, attended to, and experimented with.)
During the first year, the blind baby will progress from more generalized movements to more specific use of hands and feet. As new walkers, blind toddlers will appear to "lose" the AOP, thus bumping into objects that may have been avoided during crawling (e.g., going around kitchen cabinets or through a door opening). In reality, however, the new walker still possesses the ability but it is not at his/her disposal, as the difficulty of learning the new motor act of walking takes full use of all sensory systems to maintain balance. As the toddler develops better balance and postural security, he/she is able to use what the environment has to offer in relationship to sound and space and gradually the similar process is set in motion of experimentation, and soon the AOP emerges again.
The cane is a tool that facilitates movement, protects, detects, makes for more efficient travel, and, to various degrees, is relied upon for proprioceptive feedback (one's own feeling of moving body parts) by the child. The repertoire of motor schemes will expand with AOP as the cane traveller becomes familiar with the cane. The 0&M specialist will need to allow the child's natural need to explore the cane's effect on sound space (e.g., the child may excessively tap, bang, or hit the cane against the ground or object). As the cane skills become more familiar and the use of AOP increases while ambulating, these exaggerated movements will decrease.
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