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Focus on Physiology  April 2017
iWorx Systems, Inc.
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Focus on Physiology
April 2017

Featured Experiment

Lexical Decision Task

The lexical decision task (LDT) is a procedure used in many psychology and psycholinguistics experiments. The basic procedure involves measuring how quickly people classify stimuli as words or non-words; the participant needs to decide about whether combinations of letters are words or non-words. As an example, "GIRL" is a real word, the response should be "yes, this is a real word", but the letters "XLFFE" would have the correct response of "No, this is not a real word".

The Lexical Decision Task (LDT) 
The task was introduced by Meyer and Schvaneveldt in the 1970s. Their study was to understand how long-term memory is organized and how we retrieve information from it. In the original study, Meyer and Schvaneveldt found that people respond more quickly to words that are related in their meaning than to words that are entirely unrelated. This demonstrates that reading a word "activates" related information that facilitates the recognition of other related words. Since then, the task has been used in thousands of studies, investigating semantic memory, word recognition and lexical access in general.

In one LDT study, subjects are presented, visually, with a mixture of words and logatomes (nonsense syllables), also called pseudowords. These pseudowords respect the phonotactic rules of a language, like trud in English. The subject's task is to indicate, with a button-press, whether the presented stimulus is a word or not.

Data analysis is usually based on the reaction times and error rates for the various conditions for which the words or pseudowords differ. A very common effect is that of frequency: words that are more frequent are recognized faster. Another is based on the position of a pair of stimuli; if the pseudoword is on top of the word, the error rate is lower than if the word is positioned above the non-word. From these experiments, theoretical inferences can be drawn from differences like this. For example, one might conclude that common words have a stronger mental representation than uncommon words.

Subjects will use the iWorx data recording software and event markers to respond "Yes" or "No" when presented a series of stimuli representing words and non-words. Both timing and error rate will be determined to see how the subjects respond best to these stimuli.

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View Lab (.pdf)
Newsletter Special Offer

4-Button Response Marker

RPD-400 is a four channel hand-held, push button switch. It connects to the digital input connector of the IX-TA-220 or the IX-RA-834. When any of the four buttons are pressed, the RPD-400 delivers a TTL pulse on the corresponding digital Input. Using this response marker, an experimental subject is able to indicate a response chosen from up to four alternatives.


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