Ecological Approach to Perception
James Gibson 1966, 1979
1. Perception is in “tune” with properties of the enviornment that are useful in daily life.
2. Perception comes from exploratory activities that result in awareness of the surroundings.
What are Exploratory Movements?
Movements used when listening, touching, looking snifing and so on.
Perception and Movements are a cycle: People act in order to learn bout their surroundsings and they use what they learn to guide the actions.
HearingThese are the two best senses suited for perceiving things at a distance.
If you are visually impaired, hearing becomes the sole source of distance information
Events that cause sounds can be “localized” (the listener can tell what direction the sound came from)
Biaural hearing helps to localize information therefore a hearing impairment may cause an inability to localize auditory clues.
Objects can be identified by the sounds they make, the sounds they reflect, & the sounds produced from their interaction with objects such as a long cane.
Vision
Includes movement of eyes, head and body
Broad visual field allows perception of objects, spatial layout and and features of immediate surrounding
Spacial Acuity: the abiliyt to resolve small details
Contrast: dark against light (or vs. versa)
Contrast sensitivity and acuity are related by not the same. You can be functionally blind at night, yet have good acuity during the day.
Touch
Properties of the immediate surroundings:
Use pressure; vibration, temperature and pain
Incorporates relative positions and movements of the parts of the body (aka proprioception)
Also perceive information on skin from wind and sun.
The cane extends the “touch” by 3-6 feet
Environmental Flow
Follows the basic laws of gemetryTranslations – straight lines
Rotations – turns
Vision is the line of direction
Hearing provides a larger “field of view” because we can hear sounds from all directions.
Environment
Perceptual demands on non-visual street crossings have increased dramatically over the last few years (curbs to curb cuts, diesel to electric, volume (amount) of traffic, increased volume (auditory) of traffic, etc.)
Perceptual Learning
YOUR ROLE!! To provide opportunities for perceputal learning to occur
Gibson, 1969: Education of attention which leads from unskillful to skillfull perceiving, with practice and experiences
Unskillful
Requires MUCH:
attention and concentration;
Noticing both relevent and irrelevant information;
Attention to proximal information
(think beginning driver or new cane user )
Skillfull
Requires LESS attention; multitasking
Narrowing focus to relevant information
Attention to distal information
(Drivers with experience; person who travels frequently with cane)
Motor Learning
Motor learning is distinquished from perceptual learning and refers to ACQUISITION (through practice and experience)
Two components:Freedom: the dimension in which movement is free to vary. May teach student to “lock-up” degree of freedom
Automaticity: less attention required, the more automatic the skill (think day one of O&M and today!)
Perceptual Motor Coordination
Perceptual Motor Coordination is LEARNEDExample in book: knowing how far to turn when spoken to by another.
Cane use: knowing the depth of a step when explored with the cane.
Perceptual Knowledge
Pedestrian safety depends on proficiently adjusting your movements based on your perception of the environment.
Perception & knowledge are interrelated:Procedural knowledge: Knowing how and when to do things (different cane skills).
Episodic knowledge: knowing an area (increased speed w/familiarity, knowledge of environmental hazards and their location.)
Conceptual knowledge: knowledge of general patterns (layout and traffic patterns of typical intersections).
Successful O&M depends on good object-to-object relationships and self-to-object relationships.
Perceptual Errors
Detection Errors
Safe travel depends on detecting critical environmental features; the cane may miss enviornmental features
Curbs are no longer common at street corners as in the early days of O&M. (now have curb-cuts)
Stairs; Drop-offs
Ramps; inclining and declining
Study by Bentzen and Barlow (1995): 80 participants: 14/80 ramps detected slopes!
Canes and Perception
Sounds from the tap of the cane
Touch (from vibration on cane) and Sound (bimodal perception is better than auditory alone = less errors)
Techniques in use impact detecting characteristics
Dimensions of obstacles and openings
Distance from obstacles/openings
Crossing Streets w/o Vision
Street detection study: 22 different perceputal cues engaged 2 of which are ramp slope and audible traffic
Episodic and conceputal knowledge IMPORTANT for street detection
Alignment: traffic to align to trajectory, familiar features
Surge of traffic: difficult in complex intersections
Cognitive Mapping
Think about spatial layout (objects, path, streets)
Use information (ie sun)
Object-to-object spatial relationships (aka cognitive mapping)
Path integration (spatial updating): information about self-movement; maintaining orientation by the continuous processing of signals