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Experiment Description: Lexical Decision and Semantic Priming

The lexical decision task is a widely used task in cognitive psychology that was initially used to investigate the nature of semantic memory or the organization of general world knowledge. In this task, participants are asked to determine as quickly as possible whether a letter string is a word. In 1971, Meyer and Schvaneveldt used the lexical decision task to show that lexical decision responses are made more quickly when the current word is related to the previous word. In other words people more quickly recognize DOCTOR as a word when it follows the word NURSE than if it follows the word CHAIR. The effect came to be known as "semantic priming" and is often cited as evidence for the associative strength between concepts in semantic memory (see Chapter 8). Concepts that are more closely related will produce greater priming than concepts less closely related.

In this experiment, you will be presented with a series of letter strings and must determine as quickly as possible whether they are words or nonwords. Each letter string will be preceded by a brief presentation of real word. This experiment has three conditions: nonword, related, unrelated. In the nnword condition, the letter string will be a nonword and necessarily unrelated to the preceding word. In the unrelated condition, the letter string will be a word unrelated to the preceding word. In the related condition, the letter string will be a word related to the preceding word. You will test whether your reaction time to decide if the letter string is a word (i.e. the dependent variable) is systematically affected by the type of preceding word (i.e. the independent variable).

Participant Instructions: Lexical Decision and Semantic Priming

On each trial in this experiment, a plus sign will appear briefly in the center of the screen for 1000 milliseconds and will be immediately followed by a prime word that will remain on the screen for 700 milliseconds. The prime word will be followed by a letter string that will remain on the screen for 1000 millisceonds. The letter string will either be an English word or a pronounceable nonword. Your task is to decide, as quickly as possible and as accurately as possible, whether the letter string is a word or a nonword. You should press the / key if the string was a word, and the Z key if the string was a nonword. The computer key assignments will be displayed at the top of the screen but you may also want to tape the terms 'word' and 'nonword' to your computer keys to help you keep track of the computer key assignments.

If the response is correct, the next trial will begin in 250 milliseconds. If the response is slower than 1 second or if an incorrect response is given, a short tone will be presented and the next trial will begin in 250 milliseconds.

Half of the trials are nonword trials, one quarter of the trials are unrelated word trials and one quarter are related word trials. There are 3 blocks of trials in this experiment. The first block of 48 is a practice trial and will not count towards your results. Nevertheless, the practice trials are important for you to focus on the task and practice making your decision as quickly and as accurately as possible. The final 2 blocks consist of 60 trials each although 4 trials from each block will be removed in the calculation of the final results. You will have an opportunity to take a short break between lists.

The raw data from the experiment (112 responses) will be placed in a file called DLEX.DAT on your computer and can be examined by using the View Raw Data button.

To summarize this data, click on the Analyze Raw Data button to compute the mean and standard deviation of the reaction times for correct responses in each of the three conditions. This button will also calculate the number of valid trials for each condition or the number of trials where a correct response was provided.

The summarized data will be placed in a file called ALEX.ANL on your computer. To view the results, click on the View Summarized Data button. This summary data is important and will be necessary to prepare an APA style table to include with your paper. The file ALEX.ANL is a simple text file and can also be read and printed with any word processor. Please note that although the summary data appear in tabular form, the format is not in APA style.

To view the results of previous participants, click on the Display Group Data button. This button will display the average reaction time for the three conditions. You can use this information to compare with your own performance.

Run Experiment

If you have successfully installed Java Web Start but you are still being taken to the Java installation page, please click on this direct link to the experiment installer.

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Last Modified: Monday, 27-Jun-2005 23:33:37 MDT