Research has found that immediate serial recall for a digit series is impaired if an extra stimulus, such as the word zero appears just following the last digit to be remembered (Crowder, 1967; Crowder & Morton, 1969; Dallet, 1967; Morton, 1970). This impairment occurs even when the subject knows that the extra stimulus will routinely follow the last to-be-remembered digit on every trial and that he will not be responsible for recalling it (Crowder & Raeburn, 1970). The extra stimulus is called the stimulus suffix, and the impairment is called the suffix effect.

To explain suffix effect Crowder proposed the Precategorical Acoustic Storage theory (or PAS). The basic assumption of this theory is that there is a holding mechanism in memory for unidentified information. This holding mechanism has a duration of about two seconds. If a subject experiences a stimulus suffix, this extra information replaces one or more of the digits that the subject is trying to rehearse in short-term memory. Therefore, the subject can no longer recall those digits and therefore shows a memory impairment effect.

In this experiment, instead of remembering series of digits, you are asked to remember series of colors. Some of the series will just end (by displaying your choices for answering), while other series will be followed by a black box. This black box is NOT to be remembered. It is the extra stimulus. This experiment is attempting to find out if the suffix effect can be created for the memory of colored series, and if a black box is a sufficient "extra stimulus" to create a "suffix effect".

When this experiment begins, you will see the following screen.

Immediately after you click the START button, you will see a series of color boxes. You task is to remember the colors of the boxes in the order they were presented. Immediately after the last color in the series is presented (in the "no suffix" condition), or immediately after the black box appears (in the "suffix" condition), you will be able to enter your answers.

To enter your answers, you will see the following screen (this screen has a black box, so it is the screen for the "suffix" condition. For the "no suffix" trials, there will just be a white space instead of the black box).

You click on the colors in the order you remember the colors appearing. Every time you click on a color, it will appear just above and to the left of the START button. This allows you to see and review you answers before you submit them.

If you make a mistake entering the colors in the order you remember them, you can click the RESET button. This eliminates all your entries for this trial and allows you to start over with your entering.

You do not have to remember all of the boxes that were presented. Just do your best to enter what you remember, in the order they were presented. Try not to guess.

When you have entered all the colors you could remember, click the DONE button. This will store your answer, and will clear the screen back to just the START and RESET buttons.

Click the START button when you are ready for your next trial. There are 40 trials, but the trial numbers are not presented to avoid distraction. When you have finished the 40th trial, your results will be presented.

When you have read and understood these instructions, Please click on the word START below, to begin.