Sensation, Perception, and Pattern Recognition - Lecture Slides | PSYC 317, Study notes of Cognitive Psychology

Download Sensation, Perception, and Pattern Recognition - Lecture Slides | PSYC 317 and more Study notes Cognitive Psychology in PDF only on Docsity! Sensation, Perception, and Pattern Recognition Brandon Beltz Feb 9, 2005 Vision Basics Visual Perception
       The Fovea • Light from direct focus lands in the Fovea. • Contains almost all cones. • Acuity -- accurate, precise vision-- is best in the fovea. • Rods are abundant at the sides (periphery) of the fovea. – Good for seeing in dark. Blind spot • A blind spot appears in vision due to lack of rods or cones on the retina where the optic nerve leaves the back of the eye into the brain.           
  
  
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$  Eye Anatomy • Iris • Aqueous Humor • Pupil • Lens • Cornea • Retina • Vitreous Humor • Fovea • Blind Spot • Optic Nerve • Rods • Cones Gathering Visual Information • Saccades: Rapid eye movements. Last between 25 and 100 msec. • Fixations: Pauses between saccades. The eye takes in visual information during fixations. Eye Tracking Equipment
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 Visual Perception Difficulties • Inverse projection problem • Surface features • Object size and distance 2nd Half Outline • Iconic Memory – Sperling’s Experiments – Decay – Interference/ backward masking • Pattern Recognition – Feature analysis • Pandemonium model – Context effects and top-down processing – Object Recognition • Recognition by Components (Biederman) – Agnosia Iconic Memory Iconic Memory • Icon: a visual picture that represents an object. – Think of a computer icon • Iconic Memory also known as Visual Sensory Memory. • Visual persistence: The apparent persistence of a visual stimulus beyond its physical duration – Example: Rapidly wobble a pen between two fingers. Sperling’s Experiment (1960) • Used a tachistoscope (t- scope) to rapidly present images to the eyes. • Subjects saw a 3 x 4 grid of letters, presented very briefly (50 ms). • Whole report condition – Subjects recall any letters in the grid they could remember. • Partial report condition – Tone was sounded immediately after the grid disappeared. – Subjects recalled one row of grid depending upon which tone they heard.
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 !222 Sperling’s Experiment W. W. Norton Partial Report Condition Sperling Task D T L K L K S F J S F H Sperling Task S H D G L Z P V F G L Y Sperling’s Results • Partial report condition more accurate than whole report with immediate recall. • Partial report condition accuracy dropped quickly with time. – After 1 sec, accuracy % was same as whole report condition. Sperling’s Conclusions • Why did Sperling argue that decay is the loss mechanism in iconic memory? • How long does information remain in iconic memory? Averbach and Coriell (1961) • In a similar task as Sperling’s, a visual circle cue was used after presentation of the letters. – Circle cue used same sensory modality (e.g. vision) as letters. • Sperling used auditory cue Pandemonium Model
    

%3!0 Pandemonium Model Pandemonium Model (1959) • Types of “Demons”: – Data / Image – Computational / Feature – Cognitive – Decision • Demons represent mechanisms that interpret different levels of visual features. • Parallel processing • Bottom-up, data driven approach to processing Pandemonium Model RT predictions List 1 OQGGOEGO GOQOGGOQ GGOEGQOQ OEQQGOGO OQGGQOOG GOQOGOEO QOQOGOGG OOQGQOEO GOEOGGOQ List 2 FHLLHFLH FLHLEHHF LLFHFHEF FLEHLFLH FLHEHLFH HLHFFLHF HELFLHLF LHFLFHFL FLFHELHF Context Effects • Data Driven (bottom-up) Processing is driven by the stimulus. • Conceptually Driven (top-down) Processing is driven by higher level knowledge.     Top-Down Processing Top-Down Processing • What is This and is this 15? • What are these from?   #
4 It’s a Face!   #
   # Identifying Objects
Key Question: Supposedly objects require some type of memory representation. What are those memory representation like?
Viewer-centered representations
A mental representation of what an object looks like relative to the observer.
Object- centered representation – A mental representation of what an object looks like relative to the object itself. W. W. Norton Objects take different viewpoints W. W. Norton Objects take different viewpoints Identifying Objects- Biederman (1987) 5

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