Chapter 1 Perception

Ecological Approach to Perception James Gibson 1966, 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.

Sources of Perceptual Input Looking Listening Touching I would add smelling and tasting

Hearing These 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 gemetry Translations – 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 LEARNED Example 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

Perceptual-Motor Coordination Information about self-movement to knowledge of locations of objects in the environment. (walking and environmental flow)