Theoretical Approaches LOs Flashcards
What is the basic problem that any theory of human perception must address?
Underdetermination: when proximal stimulus info (info about distal stimulus on the receptors, eg. photons on photoreceptors on retina) cannot lead to a unique distal stimulus (object / environment, eg. tree) interpretation
Perceptual theories arise from how a magic filter eliminates all the wrong answers and only keeps the correct one (what decides the correct distal stimulus interpretation from all possible interpretations of the proximal stimulus. Eg. knowing the rectangle shown is a computer compared to the options, computer, book, phone etc.))
What are the different perceptual schools of thought
1) Structuralist Approach
2) gestalt approach
3) Neurophysiological Approach
4) Constructive Approach
5) Ecological Approach
6) Natural Computation Approach
Structuralist Approach
Perception occurs by breaking the conscious process into basic elements, describing the sensations, images and feelings. These elements are then associated in lawful ways
Connected People: Wilhelm Wundt and Edward Tichener
What it explores: basic elements of immediate conscious experience, preferred associations among elements and rules for forming associations
Example is using systematic introspection to determine structure of perceptual phenomena
PROS: starting point for psych
CONS: Introspection (own point of view) failed, low between-observer reliability, many mental processes can’t be self-observed.
gestalt Approach
Perception occurs not by breaking into individual components but by an environmental field (interaction of all things/events that influence perception).
Eg. APPARENT MOVEMENT - red ball we see as moving as one thing between two spaces instead of as two separate balls flashing
Respond to things as a WHOLE and NOT individual components
Connected people: Max Wetheimer, Wolfgang Kohler and Kurt Koffka
Percept tend towards most efficient/simplest state
Explores: what are principles of organization of environmental field, what types of functional wholes are perceived, why some functional wholes perceived while other logically possible ones are not
Example: pairs of polygons presented in rapid succesion, one was diff view of the other after having gone through transformation (translation, size scaling, or rotation), observers perceived it as a single object moving along minimum path and not two separate photos
PROS: principles of organization offered good descriptions of perceptual and physiological theory
CONS: based on demonstrations more than empirical evidence, notion of environmental field was too vaguely defined to be properly or rigorously tested
Neurophysiological Approach
Every different pattern of visual stimulation sets up a unique pattern of physiological activity
People involved: Donald Hebb, David Hubel
Investigates: what is purpose of particular physiological structure, what stimulus patterns in world do particular physiological structures respond, how is neural substrate for perception organized, how does this organization mediate perception
Example: present range of stimuli to frogs and recorded responses of individual cells in retina, recorded 4 types of cells that responded to specific stimulation (sustained contrast detectors (stick detectors), moving edge detectors (reed detectors), net dimming detectors (shadow/predator detectors), net convexity detectors (bug detectors))
PRO: assumes perception is mediated by physiology
CON: central assumption is false, can’t tell whole story about perception
Constructive Approach
Perception is process of inference, hypothesis testing and problem solving
Our knowledge of world is used to help us perceive
People Involved: Hermann von Helmholtz, Irvin Rock, Richard Gregory, Julian Hochberg
Explores: what extent do changes in our beliefs or knowledge of the world affect our perception of the world, what kinds of information or representations are used to mediate perception, how does learning or experience alter perception
Example: kept 2-D distance between two stimuli constant while stimuli were set into apparent motion, manipulated believes about how far objects were apart in depth by using diff background (plain and lines converging), found that changes in beliefs about distance affected the perceived optimality of apparent motion
PRO: perception and cognition must meet at some point, it is important to find out how and when this happens
CON: not all perception can be concept driven, some perception must be data driven and can’t be described by this theory
Ecological Approach
All info you need about visual world is available in the visual system
Visual system simply resonates to or picks out this info, perception is direct
People involved: Egon Brunswik, James J Gibson
Explores: what properties of the world are perceptually invariant, what is relationship between a perceptual invariant and behaviour that it governs or guides, what type of info does the visual system pick up from the optical array
Example: optic flow is set of velocities at each location in visual field, can get tau from it to indicate time to contact a surface, videotape evidence shows that gannets can determine time to impact when diving into sea with tau, allows birds to choose correct time to streamline bodies by folding their wings to have a safe dive
PRO: lot to be learned about perception by looking for invariants that can be derived from visual stimuli
CON: central assumption is wrong, does not appear that visual stimulation provides all the information that is required for perception to succeed
Natural Computation Approach
Visual system exploits certain properties that are generally true of the real world to compute veridical perceptions that overcome underdetermination
These assumptions are called natural constraints and reduce the number of possible distal stimulus interpretations
People involved: Whitman Richards, David Marr
Explores: what info processing problem must be solved for a particular type of perception to be accomplished, what general properties of the world must be incorporated into a solution of a problem so described, what kinds of procedures can exploit these properties in the prescribed manner and how might these procedures be implemented biologically
Example: visual system is quite adept at computing structure from motion, given a dynamic 2D pattern it can assign a 3D interpretation, proximal stimulus by itself not sufficient to uniquely determine what interpretation should be, if system assumes that objects are usually rigid then three views of four non-coplanar points are sufficient to compute 3D structure, solution is bistale as human interpretations of the phenomenon
PRO: offers precise formulation of problem of perception, good compromise between constructive and physiological theories
CON: researchers who take this approach often focus more on abstract computation than on finding out how such computations might actually be done by the visual system
