There is a peripheral vision system which is concerned with optical flow, the relative change in the position of objects on the retina as a person moves (perceptual flow). The central vision system is concerned with the characteristics (attributes) of objects in space. Perceptual flow analysis is an unconscious, automatic brain level system. Object attribute analysis is a conscious exploration of salient details.
Movement memories are made from the analysis of perceptual flow, the kinesthetic muscle memory that calculates time traveled and speed of travel. Perceptual flow memory also includes the speed of the swing of the cane as it sweeps out ahead of the blind travelers; ie. there is an arm swing memory component, as well as a leg muscle memory component. Turns in space, particularly 90 and 45 degree turns, are also perceptual flow memories.
Movement patterns develop with repetition. Kinesthetic flow memory becomes sufficient, with practice, for blind travelers to walk familiar routes without regard to landmarks. It is possible for the experienced blind travelers to daydream and walk, flowing along a familiar pattern to a familiar destination. This is a highly developed form of muscle memory sequencing, a learned motor pattern over a large spatial area.
Beginning travelers spend time locating and exploring landmarks and clues. They discover the attributes of the landmarks, the loudness, tone, location and pitch of sounds; the floor surfaces that rise or fall, sound hollow, contain bumps or dips, the rugs, the tile, the rubber mats; the kitchen odors, the smell of leather; wind currents, ceiling fans, open windows, etc. Most importantly, for every route within a spatial area, there are landmarks that contain messages for the blind travelers (the same landmark can have different messages depending on the route).
Part of the blind travelers mental map is the memory of moving past familiar landmarks. The rising and falling of the sound as they glide past, the sweep of air across the hair as they pass under a ceiling fan, the smell of cookies from the bakery, the texture of the asphalt street (picked up by the cane tip) compared to the smoother feel of the concrete sidewalk. These sensory inputs flow in at the correct time, in the correct sequential pattern, as the blind travelers moves along a route. The memories of the attributes of objects, combined with perceptual flow memory, provide the ingredients needed for experienced blind travelers to create mental maps.
Mental maps are continually forming as blind children learn to travel in space. The ingredients for mental mapping develop as young students play in their environments, and as mobility teachers show them how to gage initial position, motor plan a route, and as they practice consciously monitoring their position as they move. However, more training is needed if the advanced travelers is to understand and use mental maps to the fullest extent.
Creating and using mental maps is an adult (high school) activity. To be able to create mental maps as an adult requires that a number of pre-requisite skills be in place by high school. These include the ability to use kinesthetic input; the ability to sequence sensory inputs while moving; the ability to selectively attend to relevant information (ignoring masking information and picking out useful input from the surround; getting the figure out of the ground); and the ability to make the cognitive jump from small scale representation to large scale (so that models and maps can be understood to represent actual spaces).
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