Lecture 3: Pattern Recognition & Attention

Question 1

What are template models?

Answer 1

• 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)

Question 2

What are feature models?

Answer 2

• Features are more regular than patterns
• Complex objects composed of simple features
• Do we process patterns as collections of features?

Question 3

What supporting evidence did Neisser (1964) find for feature models?

Answer 3

• 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

Question 4

What supporting evidence did Lettvin et al. (1959) find for feature models?

Answer 4

• 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

Question 5

What supporting evidence did Hubel & Weisel find for feature models?

Answer 5

• 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

Question 6

What is beyond features?

Answer 6

• 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)

Question 7

What was the study by Avant & Lydall on masking known words vs. fake words?

Answer 7

• 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)

Question 8

How does reading illustrate top down processing?

Answer 8

• Average of 7,500 features per page (100 per sec)

- Role of top-down? not feature-by-feature

Question 9

What is the word superiority effect?

Answer 9

• 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

Question 10

What is repetition blindness?

Answer 10

• 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)

Question 11

What is the RBC theory?

Answer 11

• 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

Question 12

What are the problems with the RBC theory?

Answer 12

• Expertise and experience affects early perception of objects
• Overall (whole object) can be perceived as fast as components- not just bottom up

Question 13

What is agnosia?

Answer 13

• 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

Question 14

What is prosopagnosia?

Answer 14

• Disruption of face recognition
• But these patients typically are able to recognize other objects
• Man who mistook his wife for a hat

Question 15

What is apperceptive agnosia?

Answer 15

• 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

Question 16

What is associative agnosia?

Answer 16

• 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

Question 17

What do Agnosia studies tell us?

Answer 17

Recognition of objects is not “immediate”, but has 3 steps:

1. Perception of features
2. Integration of features into a larger whole pattern (Gestalt)
3. Association of the pattern to meaning

Question 18

Summary of pattern recognition

Answer 18

• fast
• apply to novel patterns
• across orientations, occlusions
• involves features
• augmented by top-down (conceptually driven) processes
• multi-step process: feature detection, integration, association

Question 19

What is attention?

Answer 19

“The mental process of focusing effort on a stimulus or on a mental event”

Question 20

What are the two main types of attention?

Answer 20

1. Visual Attention

2. Selective Attention

Question 21

What is visual attention?

Answer 21

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?

1. Space-Based Visual Attention
2. Object-Based Visual Attention

Question 22

What is space based attention?

Answer 22

• 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)

Question 23

What is the spotlight Metaphor (space based attention)?

Answer 23

• 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

Question 24

Why space based attention?

Answer 24

Exogenous cues: draw attention to potentially important
events in space
Endogenous cues: place attention according to expectancy

Question 25

What is object-based attention?

Answer 25

• Attention is placed on objects

- within-object processing is more efficient (faster, more accurate) than across-object processing

Question 26

What was Lavie and Driver’s (1996) study on object based attention?

Answer 26

• Line (object) study
• near and far conditions showed that it was not about the distance between the lines because they were the same distance so they concluded that it was about switching from one object to the other
• Faster to targets (dots or gaps) on same “object” (line)
• Object based attention

Question 27

Why object based attention?

Answer 27

• major goal of vision is to identify objects

Question 28

What is the filter theory (Broadbent, 1958)

Answer 28

3 components:

• selective filter
• limited capacity decision channel
• long term memory (detection)

Question 29

What is the evidence for the filter theory?

Answer 29

• when told to recall by ear (left ear: 4, 7, 3 vs. Right ear: 1, 9, 5): 65% of items. Attend to one ear then switch quickly to other.
• told to recall sequence (4-1, 7-9, 3-5: only 20% of items. Requires rapid switching of the selective filter.
• suggests select info based on channel (i.e., left channel vs. right channel)

Question 30

What is selective attention?

Answer 30

SM has a large capacity but does not last very long. Need to quickly select information out of SM for further processing. How is this done?

• filter theory
• Attenuation theory

Question 31

What was Cherry’s research on selective attention?

Answer 31

• Dichotic presentation: shadowing
• He Varied the content of unattended: change male/female (easy to detect) OR changed language (did not notice language change)
• suggests that we attend / select using physical cues

Question 32

How did the class Demo/ Moray’s study challenge or demonstrate problems with the filter theory?

Answer 32

• Class demo (Girl reading in monotone/choppy voice, guy shadowing and Prof. reading magazine in same voice. Then they do it again but instead of reading the magazine in a choppy voice prof says the guys name in a bunch of sentences. The guy shadowing hears his name even though it was in his unattended ear)
• Moray (1959) person’s name on unattended channel (aka the cocktail party effect)

Question 33

How did Gray & Wedderburn’s study challenge the filter theory?

Answer 33

• dichotic presentation (one stimulus to one ear and a different stimulus to the other ear at the same time. Car and 3, 9 and Pen, Ter and 5)
• They found that people did not organize it by channel or ear but rather responses were organized by word/digit (i.e., Carpenter 395)
• Shows: Selected by semantics

Question 34

How did Corteen & Wood’s study challenge the filter theory?

Answer 34

• Phase 1: Presented people with little shocks (UCS) which lead to a galvanic skin response (UCR). Paired shock with names of cities (CS) and eventually they would present just the city name without a shock and people would have a galvanic skin response
• Phase 2: Dichotic listening. Old (Denver) and new city names (Toronto), Attended vs. unattended ears (according to Broadbent’s filter model if the city name comes up in the unattended ear then they should not have a GSR because they did not process it.)
• Results: GSR’s unattended=attended (equal magnitude). GSR’s to old and new names.
• Conclude: semantic info from unattended is processed (against Filter Theory)

Question 35

What is the Attenuation theory (Treisman, 1964)?

Answer 35

• Filter: Is not all-or-none, Just attenuates, Uses physical
• Dictionary units: “lexicon” (logogens- logogens are mental representations of words in our lexicon. Logogens operate like neurons). Affects detection.
• Thresholds: Variable (name vs. house). Logogens have different thresholds, words that are significant to use have low thresholds (e.g.., your name)