Lexical Decision
Introduction
The term “lexical” refers to the words or vocabulary of a language. Our lexicon includes all the words that we have in our vocabulary, which is a subset of all the words in our language. Someone who knows a lot of words and has a large lexicon can distinguish among many words in a particular language through, for example, their exposure over many years to reading and hearing words used in books and conversation.
Description of Activity
During this activity, you will perform a task called lexical decision to measure how quickly you can classify stimuli as either words or non-words. Your job will be to make your decision as quickly and as accurately as possible. For example, you may be presented with a stimulus such as “NURSE,” which is a word, or “SNRUE,” which is a non-word. You will be presented with many words or non-words during a series of trials. At the beginning of each trial, you will be presented with a fixation “+,” and then you will be presented with a stimulus that will stay on the screen until you respond. You will press one key if the stimulus is a non-word and a different key if it is a word. Try to be fast but also accurate in signaling your decisions. Note that this activity shows you words or non-words visually but the same task could be performed with words presented auditorily. The only difference then would be that you would rely on the sound rather than the visual form to decide whether the stimulus is a word or non-word.
Decision Speed for Words and Non-Words
One thing you may notice as you do the trials is that you may feel that you make decisions quicker when you are presented with an actual word. Your decisions are made so quickly that you may press the button before you register the actual meaning of the word. How is your accuracy and reaction time (i.e., decision speed) for words compared to non-words? You can see by looking at your results at the end of this activity.
Decision Speed and Word Frequency
Why are words decided faster than non-words? A simple explanation is that you have accumulated a lifetime of experience by reading and hearing actual words. It is rare that you have encountered most of the non-words that you will encounter in this activity. The increased frequency of experience with the actual written visual form of words is much greater than that for non-words. Your perception for a word is therefore much quicker than that for non-words even before your mind has time to address what the word means, which for non-words is nothing at all. Among the set of actual words in your lexicon, there are some words like “the” that are encountered very frequently in daily reading, whereas a word like “thou,” which you have surely encountered at some point, is far less frequent in modern usage. Which word—“the” or “thou”—do you think you will make a lexical decision about quicker? Why?