Word Recognition

Psy315 - Class 8

(This page last updated 2 October, 2006.)

 Basic Paradigm

• Word presented for brief period (for example, 50 msec).
• Mask appears at position occupied by word to limit processing time.
  • generally looks something like "####"
• Subject reports identity of word.
  • Measure accuracy across many trials.
• From trial to trial, the exposure time for the word changes.
• The shortest possible exposure time for which the word can be identified accurately is the exposure threshold.

Word Frequency

• Some words are used more frequently than others.
• High frequency words are recognized more accurately than low frequency words.
  • Exposure threshold shorter for high frequency words.

   

Repetition Priming

• Two parts to experiment.
  • Read list of words aloud.
    • Activates these words in memory.
  • Word recognition test using basic paradigm (fast exposure followed by mask)
• Recognition accuracy better for words on original list.

   

Word Superiority Effect

Display Sequence

• Word displayed briefly.
• Mask at word position.
• Subject reports letter at position indicated by arrow by selecting one of two choices.

     

• Letter identification better when it is embedded in word than when it appears alone.
• Letter identification also better when in pronounceable nonword (REET), but not when in nonpronounceable nonword (WVJB).
• The context of the word aids the perception of the individual letters within the word.

   

Feature Net Model of Word Recognition

Detectors connected to one another and arranged in hierarchy.

• feature detectors
• letter detectors
• word detectors

 

How does the Feature Net explain the effects of word frequency?

• Before a word is seen, different word detectors start out with different levels of activation.
• A high frequency word starts with a high level of activation.
  • Only a little additional activation from the stimulus is needed to trigger recognition.
• A low frequency word starts with a low level of activation.
  • Much additional activation from the stimulus is needed to trigger recognition.

 

How does the Feature Net explain the effects of repetition priming?

• After a word is seen the first time, its activation remains higher than normal.
• If the word appears again soon afterward, it will require less activation to trigger recognition.

 

The simple Feature Net cannot explain why words and pronounceable nonwords are easier to perceive than nonpronounceable nonwords.

• Add extra layer of detectors for bigrams (letter pairs) between letters and words.
• Pronounceable nonwords will have many of the same bigrams that appear in real words.
• Nonpronounceable nonwords will not have as many of these bigrams.
• When a pronounceable nonword (HICE) appears, there will be bigram detectors ready to respond to many of its letter pairs (HI, CE).
• A nonpronounceable nonword (RSFK) will not generate as much activity in the bigram detectors, and it will thus not be recognized as easily.

next class: Object Recognition

Psych 315: Cognitive Psychology Kyle Cave Psychology Dept. U. Mass.