EXPERIMENT DESIGN: Stage 2: Elaborate the Trial Procedure [37329]

This section builds upon the basic design that was laid out in Stage 1. Following the guideline of iterative design and development, Stage 1 defined the most simple trial procedure: present a probe stimulus and collect a response. Now we are ready to elaborate the trial procedure by adding a Prime Display. In a priming version of a lexical decision task, the participant is presented with a text string prior to seeing and responding to the Probe Display. The question of interest is whether the nature of the Prime Display influences the response to the probe word.

As always, start with the abstract. The original abstract is copied below, with the new prime manipulation information underlined:

The experiment will measure the time to make a lexical decision after first seeing a priming word. The independent variables are whether a letter string is a word or a non-word, and whether the Prime Display is the string “Word” or “Nonword”. The participant will be presented with a fixation (+) displayed in the center of the screen for one second. Next, a priming word will be displayed for one second. Then a Probe Display will present a letter string stimulus in the center of the screen for up to 2 seconds. The stimulus display will terminate when the participant responds. Participants are to respond as quickly as possible as to whether the stimulus was a word or a non-word by pressing the “1” or “2” key respectively. The dependent measures are the response (i.e., key pressed), response time, and response accuracy of the Probe Display. The stimuli will be words and non-words, presented in random order in black text on a white background.

The goal of Stage 2 is to elaborate the basic Fixation-Probe trial procedure by adding a priming manipulation. A display will be added at the beginning of the trial procedure to permit the participant to pace the trials and instructions will be added to the Fixation display to remind the participant of the response keys. Also, a Prime Display will be added prior to the Probe Display, and Feedback will be added to the end of the trial procedure.

There are two major steps to Elaborating the Trial procedure, as shown below:

Stage 2, Step 1: Add the Missing Delays and add Instructions to Existing Displays

In Stage 2, three new displays are added to the trial sequence, and instructions are added to the existing prime and Probe Displays. A trial now looks like the following:

Get Ready Display

The Get Ready Display will enable the participant to begin the trial when he or she is ready; the “Get Ready” message will remain on the screen until the participant presses the designated key.

Fixation and Probe Display Instructions

Instructions will be added to the Fixation display to remind the participant of which keys they are to press for which response:

Press the 1 key for a word

Press the 2 key for a nonword

These instructions will remain on the screen for the Prime and Probe Displays. The instructions should be positioned on the screen so that they do not interfere with the presentation of the Probe Display.

Prime Display

The Prime Display is the string “word” or “nonword”*** . For data analysis purposes, the string that was presented on the Prime Display will be logged.

Feedback Display

The Feedback Display tells the participant whether or not their response to the trial was correct. It is typical to include feedback on experiments measuring reaction time or response accuracy as a way to help keep the participant motivated and focused on the task. It is typical to display feedback as follows:

• A message indicating whether the participant’s response was correct or incorrect
• Reaction time to the stimulus
• Cumulative response accuracy

The Get Ready, Prime, Probe, and Fixation displays can be created using either a Slide or TextDisplay object. View E-STUDIO: Slide Object [22701] and E-STUDIO: TextDisplay Object [22705] for more information on those E-Objects.

View E-STUDIO: FeedbackDisplay Object [22709] for more information on implementing a Feedback object.

Stage 2, Step 2: Verify the Get Ready, Prime, and Feedback Objects
At this point, the three new displays and the two modified displays have been designed. Again, you should be able to envision and draw out the displays that the participant would see. In the case of the Stage 2 version of this experiment, expect to see displays like the following:

***There are numerous variations of the Lexical Decision task. In many of them, the Prime manipulation is a more complicated one, whereby the Prime is a word that is related to the probe, a word that is unrelated to the probe, or a nonword. For the purposes of this chapter, the Prime manipulation is a more basic one, and serves to illustrate the general trial procedure for including a Prime Display prior to the probe.

Next Article: GETTING STARTED: Stage 3: Add All Conditions, Set Number of Trials, and Sampling [37330]
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