Perception & Pattern Recognition

Sensation, Perception and Pattern Recognition Epistemology Study of the origin and nature of knowledge Psychophysics Study of the relationship between physical changes of the world and the psychological experiences associated with theses changes Copyright © Allyn & Bacon 2005 Sensory Experience       vision (seeing – job of eyes) audition (hearing/listening -- job of ears) gustation (taste –job of tongue) olfaction (smell –job of nose) somatic sensation (touch –job of skin, internal organs) vestibular sense (balance, orientation in space – job of vestibular apparatus [near ear] ) Transfer of sensation to the brain for higher-order processing is the job of the Peripheral Nervous System (PNS) Copyright © Allyn & Bacon 2005  Peripheral Nervous System (PNS) Peripheral Nervous System (PNS): All neural tracks that run from spinal cord to muscles, organs, glands & other tissue  The PNS comprises the Somatic, Autonomic & Diffuse Enteric nervous systems   Somatic Nervous System (means “to the body”)  The branch of the PNS that transmits signals from the sensory organs to the CNS & from the CNS to skeletal muscles  Directs voluntary movement Autonomic Nervous System (ANS) [less directed by CNS]  The branch of the PNS that connects the CNS to the internal muscles, organs and glands  Directs involuntary movement/ regulates internal environment  Sub-divided into 2 parts: sympathetic (energizing) & parasympathetic (calming) Copyright © Allyn & Bacon 2005 Peripheral Nervous System (PNS)   Autonomic Nervous System (2 sub-divisions)  Sub-divided into 2 parts: sympathetic (energizing) & parasympathetic (calming) ~Sympathetic = the division that heightens arousal and energizes the body for action ~Parasympathetic = the division that reduces arousal and restores the body to its preenergized state Important for emotion Diffuse Enteric Nervous System  “added on” third division  Internal autonomous neuro-system of the digestive tract Copyright © Allyn & Bacon 2005 Organization of the Nervous System CNS - red/orange PNS - yellow Copyright © Allyn & Bacon 2005 Sensation All Sensory Systems Must Perform the Following tasks: 1. pick up stimulus in the form of physical energy from the world around us. change that physical energy into a pattern of neural impulses (process of transduction) carry those impulses to the proper locations in the brain (through electrochemical communication in neural circuits). 2. 3. 4. process the information contained in the pattern of impulses so that the stimulus can be identified, attended to and organized. Copyright © Allyn & Bacon 2005 Are you ticklish? What do you see when you rub your closed eyes? Sensation to Perception Finished files are the result of years of scientific study combined with the experience of many years. Copyright © Allyn & Bacon 2005 Sensing and Perception Process ― Copyright © Allyn & Bacon 2005 Sensing and Perception Process •Sensation The processes by which our sense organs detect energy from the physical world. •Transduction The process by which physical energy is converted into sensory neural impulses. •Perception The processes by which people select, organize, and interpret sensations Copyright © Allyn & Bacon 2005 Sensing and Perception Process ―We see, hear, smell, taste and feel the sensations of the world as the first link in a chain of events that subsequently involves coding stimuli; storing information; transforming material; thinking, and finally, reacting to knowledge.‖ External Stimulus Energy Internal Processing Sensory System Transduction Sensory detection iconic/echoic storage CNS Activity and coding Memory and Transformation Overt Activity Representation of the information processing stages suggested By Cognitive Psychology Copyright © Allyn & Bacon 2005 Sensing and Perception Process  Illusions  ―Real‖ and perception don’t match– erroneous perceptions of reality that are generally shared by all people   Distinction between sensations and reality (between information sensory systems receive and what the mind interprets) Perceptions are influenced by past knowledge, previous hypotheses and prejudices as well as sensory signals Copyright © Allyn & Bacon 2005 The Müller-Lyer Illusion Copyright © Allyn & Bacon 2005 What we sense (in our sensory organs) is not necessarily what we perceive (in our mind) Copyright © Allyn & Bacon 2005 What we sense (in our sensory organs) is not necessarily what we perceive (in our mind) Sensing and Perception Process Perception processes (process of selection, organization, and interpretation of sensory signals) is a combination of:  Stimulus energy received and transduced by the sensory system and sent to the brain  Knowledge stored in memory from past experience Combination of specific information from senses and abstract representations from memory– we use the integration of the two to make sense of what we perceive! Copyright © Allyn & Bacon 2005 Pattern Recognition   Involves interaction between sensation, perception and memory Principles:      Recognize familiar patterns Evaluate unfamiliar objects Perceive different orientations Identify occluded objects Quickly recognize patterns Copyright © Allyn & Bacon 2005 Percept: a mental representation of a stimulus that is perceived Copyright © Allyn & Bacon 2005 Sensing and Perception Process Copyright © Allyn & Bacon 2005 Subjective Organization     Human’s tend to ―see‖ things in the physical world that do not exist (illusions) Evolutionary necessity– need to see forms, edges & motions crucial for survival Neurological explanation- illusionary contours activate neurons in the visual cortex Gestalt explanation– create subjective illusions because of tendency to see simple, familiar or ―good‖ figures in our environment–  Law of Pragnanz: we tend to perceive the most likely, simple visual organization of environmental stimuli into a stable and coherent form (the whole) Copyright © Allyn & Bacon 2005 Gestalt Theory  Pattern organization    Stimuli work together to be more than their component parts Patterns of stimuli are naturally/spontaneously organized  Early = function of stimulus itself and only minimally related to experience with the object  Cross cultural research = ―natural‖ organization of patterns is directly tied to the perceptual history a person Principles of Organization  Based on Laws of Grouping  Natural organization can be re-organized spontaneously or voluntarily controlled  Past memories (world experience) influence organization Copyright © Allyn & Bacon 2005 Principles of Organization Gestalt Laws of Grouping  Proximity  Seeing 3 pair of lines in A Seeing columns of orange and red dots in B Seeing lines that connect 1 to 2 and 3 to 4 in C  Similarity   Continuity   Closure  Seeing a horse in D  Common Fate Copyright © Allyn & Bacon 2005 Principles of Organization Gestalt Laws of Grouping  Tend to organize even completely novel stimuli into units a) b) c) d) e) Tendency to see the object (a) as a triangle and an ―n‖ shape— Subjects recognized (b) and (c) faster than (d) and (e) Copyright © Allyn & Bacon 2005 Principles of Organization 1) 2) •1) Natural organization can be re-organized spontaneously or voluntarily controlled •2) Past memories (world experience) influence organization Copyright © Allyn & Bacon 2005 Theoretical Approaches to Perception  2 Biggies:  Direct perception-- Bottom-up view of processing     Physical stimulus is the important element Learning and higher cognition are seen as minimal/unnecessary Gibson: rich info in optic array matches richness of the world Views perception as direct acquisition of information from the environment  Constructive perception-- Top-down view of processing    ―actively construct perception by selecting stimuli and merging sensations with memory‖ based on high-level cognitive processing, prior knowledge and existing expectations Unconscious inference = a process of spontaneous integration of information from sensory signals + learned world experience = perception Recognize your mom with hot pink hair Both views work well to explain perception but focus on different phases of the process! Copyright © Allyn & Bacon 2005 Example of Bottom-Up vs. TopDown Processing    Bottom-up: Pattern recognition is initiated by the parts of the pattern that lead to the recognition of the whole pattern (2 eyes, 2 ears, 1 tail, 4 legs oh, it’s a dog). Top-down: Recognition of the whole pattern leads to recognition of the component parts (it’s a dog oh, so it has 2 eyes, 2 ears, 1 tail, 4 legs) . Palmer & others: Simultaneous process (both happen at same time) though certain tasks/ situations may lead to one type of processing over another. Copyright © Allyn & Bacon 2005 4 other Main Theories of Bottom-up Pattern Recognition Template Matching  Structural-Description (Geon Theory)  Feature Analysis  Prototype Matching and Canonic Perspectives  Copyright © Allyn & Bacon 2005 Template Matching  Pattern recognition occurs when a EXACT match is made between sensory stimuli and an internal mental representation held in memory– such that…     Light energy emanating from an object falls on the retina and is transduced into neural energy which is transmitted to the brain a search is made among existing mental templates if a template is found that matches the neural pattern, the person recognizes the object after a match between the object and its template is made, further processing and interpretation may occur Copyright © Allyn & Bacon 2005 Computer examples: Bar codes and Checks Template Matching  Strengths of Theory:   Useful conceptual and practical applications Seems apparent that to recognize some visual form, some contact with a comparable internal (mental) form is necessary– need to match memory Literal interpretation does not work  Object with slight difference from template would mean no recognition so need Zillions of templates to be stored– neurologically not possible  Too long to do– to much time to sort through the zillions of templates stored  Can’t account for unfamiliar objects  Weaknesses  SSSSSSSSSSSSSSSSSSSSSSSSSSSSS Copyright © Allyn & Bacon 2005 Geon Theory  Biederman (1982): Human information processing system has a limited number of simple geometric ―primatives‖ that are applied to complex shapes  Recognition by components, so bottom-up processing   Complex shapes made of geons (geometric ions)– like alphabet has 26 letters that make up words, 36 geons make up shapes Only edges are needed to define geons (and build a pattern leading to recognition) so color, texture & small details don’t matter (as they would in template matching)– confirmed by research Copyright © Allyn & Bacon 2005 Geon Theory 3 geons in all combinations= 1.4 billion 3 geon objects Support for geon theory (object identification is grounded on seeing basic forms) is found in that removal of crucial relational information makes objects harder to identify Copyright © Allyn & Bacon 2005 Feature Analysis  Pattern recognition occurs after incoming stimuli have been analyzed according to their simple features  Stimuli are thought of as combination of elemental features– the elements & specification for combining ARROW  A= and and  Similar to bottom-up processing  Advantages over template model:  Features are simpler so system corrects for problem in template matching  Possible to specify most important relationships among features and note unimportant details AAAAAAAAAAAAAAAAAAAA Copyright © Allyn & Bacon 2005 Feature Analysis  Behavioral evidence  Eye movement research suggest the more information carried by a feature, the longer eyes stay fixed on it  Suggest attention and purpose element of pattern recognition  Neurological evidence  Nerve cells sensitive to orientation of lines –fire for either horizontal or vertical  Nerve cells sensitive to only edges of visual stimuli, some to lines and others to right angles  If image forced to stay on exact same spot of retina (rather than normal eye movement) neural pathway gets fatigued and stop responding– parts of a object start to disappearsuggests features are important units in perceptions H B H B 3 4 Features like vertical bars drop out Copyright © Allyn & Bacon 2005 Prototype Matching  Pattern recognition occurs when a match is made between a perceived pattern and a prototype (an abstracted mental pattern held in memory-- a ―Best‖ representation of the pattern)  Searching for resemblance instead of exact matches  Allows for recognition of a pattern that is unusual but in some way related to a stored prototype  evaluate prototype of ideal ―S‖ or ―A‖ and see how close ―S‖ and ―A‖ match the model  If degree of mis-match is great, we recognize lack of match and may search for a prototype that fits better  More compatible with neurological economy and memory search processes than template matching  But does not account for detailed discrimination (Q vs. O) template matching better model Copyright © Allyn & Bacon 2005 Draw a triangle   Draw a cup and saucer Draw a TV Copyright © Allyn & Bacon 2005 Canonic Perspectives  Views of an object/image that first comes to mind when asked to recall– ―best‖, most representational view   Can be formed from experience with exemplars (like members of a category) Research supports: through common experience with objects, we develop the most representational view of an object/ a view that discloses the most information about it and store it as a permanent memory Copyright © Allyn & Bacon 2005 Top-Down Processing    The perceiver builds (constructs) a cognitive understanding (perception) of the stimulus Called Intelligent Perception because higherorder thinking is key. Emphasizes role of learning and memory  Perception both affects and is affected by the world as we experience it. Copyright © Allyn & Bacon 2005 Top-Down Processing  Quickly form and test various hypotheses regarding percepts based on    Sensory data Knowledge stored in memory Unconscious inference (combined information from sensation and memory to make judgments we are unaware of making)  Explains effects of context where bottom-up does not Copyright © Allyn & Bacon 2005 Top-Down Processing  Context plays a role:  Context Effect: world knowledge facilitates identification of objects in familiar contexts and hinders identification of objects in inappropriate ones    Research shows that accuracy and time required to identify objects are related to the appropriateness of the object’s location in the scene Research shows word context can be used to supplement feature information in the recognition of letters When context or general knowledge of the world guide perception = Top-down processing–- because high-level general knowledge contributes to low-level perceptual units Perception of an object is greatly influenced by a person’s expectations as determined by the context (we “see” what we expect to see) Copyright © Allyn & Bacon 2005 Top-Down Processing Object happen in context, so context plays a role: Parts of face recognizable in context, ambiguous when alone but recognizable when more details or information shown Copyright © Allyn & Bacon 2005 Pattern Recognition   The previous theories aren’t ―right‖ or ―wrong.‖ They each provide a piece of the puzzle of how we perceive information We use a combination of sensory information and abstract memory to make sense of what we perceive. Copyright © Allyn & Bacon 2005