Lecture 3: Pattern Recognition & Attention Flashcards
What are template models?
- Match stimulus to template in memory
- Support for idea: computers/ scantrons
- Limits: inefficient, irregular world, strict match (lead people to go to something a little more simple, feature models)
What are feature models?
- Features are more regular than patterns
- Complex objects composed of simple features
- Do we process patterns as collections of features?
What supporting evidence did Neisser (1964) find for feature models?
- High speed scanning (this is behavioural evidence for feature processing)
- When people look at patterns they extract those Features and the system makes notes of those features and then their compared to some type of representation that we have stored
- Compared to “z” features
- When the letter z is with other letters that don’t share features, people find it more quickly. When it is with letters that do share features, it is harder and takes much longer
What supporting evidence did Lettvin et al. (1959) find for feature models?
- Microelectrodes into cells of frog retina
- Recorded activity: Edge detectors, Moving edge, Dimming, Convex edge (small, circular dot moves)
- All these cells process certain types of features, tells the frog that a fly is going by.
- Shows the existence of feature detectors
What supporting evidence did Hubel & Weisel find for feature models?
- Simple cells (these cells only respond to): Simple patterns of light, Location specific, Edge, slit, line
- Complex: Same as simple, but not location specific
- Hypercomplex: Moving lines
- W,x,y: Movement speed
What is beyond features?
- We also have Top-down (conceptually driven) pattern recognition
- Gestalt grouping principles: processing of “whole” object
- Neuroimaging evidence shows specialize brain areas for processing of whole visual objects
• Pattern recognition is influenced by knowledge (random mix of letters from the word university vs. the word university)
What was the study by Avant & Lydall on masking known words vs. fake words?
- Masking of Boy vs. YOB
- Results: a shorter interval is required to erase (mask) BOY than YOB (because we recognize boy as a pattern and have knowledge of it, we have to shorten the interval and get at it quicker in order to erase it)
How does reading illustrate top down processing?
- Average of 7,500 features per page (100 per sec)
- Role of top-down? not feature-by-feature
What is the word superiority effect?
- Reicher (1969),Wheeler (1970)
- They showed people a single letter, and masked it. After they masked it, they ask you whether the letter was a D or G. The accuracy is about as low as chance if the interval is at the right time. Then they put the same letter “D” but at the end of the word, “wind”, and then they masked it and asked them if they saw the word wind or wing.Not much has changed except it is now a letter at the end of a word instead of a letter on its own. Even though there are more features to process here, they actually perform much better (they are really accurate).
- Performance better with wind than D
- Top down influences pattern recognition
What is repetition blindness?
- Use of RVSP (rapid serial visual) paradigm (Morris and Harris, 2002)
- Show people a series of items in the same spot rapidly
- “when she spilled the ink there was ink all over”
- People fail to see stimulus (“ink”) the second time
- Top down influence: cognitive system has identified the stimulus, so “expect” NOT to see it again (system has already processed it and is inhibiting us from seeing it a second time)
- “I broke a wine class in my class yesterday”. People read “wine glass” (top down context biases)
- Also, expect repetition blindness to class- class, but there was no repetition blindness to the 2’nd class: top down (“glass”) overrides effect (“glass”-“class”)
- Tells us that Top down influences pattern recognition (word knowledge effects pattern processing)
What is the RBC theory?
- Recognition by components theory (Beiderman, 1987, 1990)
- Objects made up of combinations of “geons”
- Recognition involves:
- 1’st parse objects into component geons
- note where geons join (find edges)
- match geon combinations to representations in memory
- very bottom-up model
What are the problems with the RBC theory?
- Expertise and experience affects early perception of objects
- Overall (whole object) can be perceived as fast as components- not just bottom up
What is agnosia?
- Greek: Prefix “a” meaning “not” and “gnostic” meaning to “to know”
- Agnosia is a failure or deficit in recognizing objects:
- Pattern of features cannot be synthesized into a whole
- Or person cannot connect the whole pattern to a meaning
- Caused by specific brain damage
What is prosopagnosia?
- Disruption of face recognition
- But these patients typically are able to recognize other objects
- Man who mistook his wife for a hat
What is apperceptive agnosia?
- Disruption in perceiving whole patterns
- Can process basic features (lines, Colours)
- Cannot integrate into a whole object
- Typically have damage in the right hemisphere parietal area
What is associative agnosia?
- can combine features into a whole, can copy or describe a drawing
- cannot associate with a meaning (cannot identify)
- involves temporal lobes of both hemispheres
What do Agnosia studies tell us?
Recognition of objects is not “immediate”, but has 3 steps:
- Perception of features
- Integration of features into a larger whole pattern (Gestalt)
- Association of the pattern to meaning
Summary of pattern recognition
- fast
- apply to novel patterns
- across orientations, occlusions
- involves features
- augmented by top-down (conceptually driven) processes
- multi-step process: feature detection, integration, association
What is attention?
“The mental process of focusing effort on a stimulus or on a mental event”
What are the two main types of attention?
- Visual Attention
2. Selective Attention
What is visual attention?
Sensory memory has a large capacity. However, to be efficient, we must be able to select the most relevant information from the environment. How is this done?
- Space-Based Visual Attention
- Object-Based Visual Attention
What is space based attention?
- Direction of visual attention can be separated from direction of gaze (eyes). We can disassociate them (e.g., driving. Good drivers know what’s happening around them, your gaze has to be up front but you also have to know what’s happening beside you and behind you )
- Endogenous: internal/intentional (a top down process)
- Exogenous: drawn by external cue (not me moving my attention, something else moving it) (bottom up process)
What is the spotlight Metaphor (space based attention)?
- Visual attention as a spotlight
- Spotlight focused (endogenous or exogenous) on locations in space
- Spotlight facilitates processing or information at the attended location (information at unattended location does not get processed as efficiently)
- Information at unattended locations is inhibited
Why space based attention?
Exogenous cues: draw attention to potentially important
events in space
Endogenous cues: place attention according to expectancy