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Lecture 11

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Carleton University
PSYC 2700
Chris Herdman

Lecture 11 Visual processing - Getting words into the system involves translation of written symbols into meaning Involves eye movement - Series of pauses (fixations) and jumps (saccades) • Fixation ~ 250 ms (80% of content words) • Saccade ~ 10-20 ms  Jerky movement of eye - Why series of fixations and saccades? • Visual acuity best at foveated area • High resolution is where we foveate in order to pick up details of words Two assumptions - Immediacy • Reader attempts to interpret each (content) word (not the, of, but) as it is encountered • Some words take longer to interpret - Eye-mind • Eye will remain fixated on a word as long as the word is being processed Evidence 1 - Gaze-contingent paradigm (Rayner) • If cover the foveated letters such that the parafoveal can be seen?  Where the person was looking, they would cover the word so you couldn’t see it. You would see a blank spot where you were foveating  Reading rate drops from 300 wpm to 50 wpm  Shows that foveating words is critical Evidence 2 - Skipping Words (Carpenter and Just) • When skip a word, it is usually a function word (the, and, but)  Don’t usually skip content words • Skip more often with easy text • Fixate on certain words longer than others Evidence 3 - During Normal Reading • If change next word during saccade?  It takes 20ms for us to jump from one word to the next  During this jump, researchers would change the next word (during the saccade)  People do not notice  Shows that very little of next word is pre-processed Evidence 4 - Fixations and Reading Skill • Fixation patterns of high skill vs. low skill readers differ • Good readers  Systematic fixations  From one word to the next in a steady pattern • Low skill:  Require more fixations  Backtracking (go back to words they already read)  Longer fixations per word • Speed reading increases the time you read but decreases your comprehension Visual word recognition - Encoding of words and activation of their corresponding orthographic, phonologic, and semantic representations • Orthographic visual word form/knowledge, phonological sound, semantic activates meaning - Tasks: • Eye tracking • Lexical decision (decide if a given item is a word or not) • Naming (the word out loud) How to model word recognition? - Center model around robust “marker” effects - Then start to build around these effects Marker effect - Word frequency: common vs. less common words • Common = process more quickly, less common = process slower - Word frequency affects: • Fixation time  It takes more time to activate mapping of uncommon words  It takes less time to map and recognize common words • LDT (lexical decision time) • Naming  Less time for common words (doesn’t match a spelling known to the brain) Morton’s (1969) Logogen model - Logogen: • 1 per known word • Orthographic (word form) and phonological (sound) attributes of each word  NO SEMANTIC VALUE • (1) Information accumulator  Information accumulators bring in information, logogen activation for ‘HOUSE’ and then it will exceed a threshold and fire, resulting in naming of ‘HOUSE’ • (2) Resting activation level  After firing, the activation lowers back to normal resting levels • (3) Threshold  Vary depending on nature of the word  Firing threshold = lower for common words than for less common words  Because it takes LESS activation to recognize a common word - Frequency effect? • Assume threshold is lower for common words  For common words the amount of activation is already high because we commonly see these words, therefore less activation is needed to make words like “the, house, car” activated in our brain Context (priming) effects - Does meaning affect word recognition? YES! • Example: DOCTOR  NURSE • We are faster to name the second word if the first word is related - Assume there’s a separate system in which meaning is stored (context system) - Activate logogen for ‘DOCTOR’(in logogen system), then there is a spread of activation to the meaning of ‘DOCTOR’(in context system). This spread will then spread to other related concepts such as ‘NURSE’or ‘HOSPITAL’ - Through meaning we get the priming effect - Our processing decreases if the prime is related because it already pre-activates those related w
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