Learning to use E-prime
By the end of this tutorial you should:
· understand lists, procedures, text displays, feedback displays and image displays;
· be able to randomise lists of stimuli, add new stimuli to an experiment (text and images), specify a correct response for stimuli;
· alter the duration of a stimulus
· collate data and obtain means for different conditions.
Step 1. Open E-prime from Start>programs>E-prime>e-studio. You will be presented with the start screen:
Step 2. You are going to design an experiment with the following instructions:
You are going to see a series of pictures and words. Each stimulus will be preceded by a fixation cross. Please stare at the cross before the stimulus appears. When the stimulus appears press Z if it is an animal, and M if it is furniture.
First you should type in the instructions. Double click on Session Proc in the structure window. This opens a procedure line in the workspace. Drag a text display from the toolbox onto the procedure line:
Then double click on the text display icon in either the procedure line or the structure window. This opens the text display in the workspace. Type in the instructions.
Now we need to tell the computer to display those instructions until the subject presses the space bar. Click on the property pages icon of the text display. This opens the properties of the text display that you are working with:
Step 3: Create a list. Lists are created when you have one or more blocks of stimuli that need to be repeated in a series of trials. This experiment has two blocks, one using words and one using pictures. We will need three lists in total. The first list will contain the ‘wordblock’ and the ‘imageblock’. Both of these blocks need a list of their own that will be subordinate to the first list.
Drag a list icon from the tool box and place it on the procedure line after the text display. Double click on the list in the procedure line to open it in the workspace.
Step 4: creating a subordinate procedure.
Next, double click on wordproc to open the procedure line in the workspace. Drag two text displays onto the line and one feedback display. The first text display will be our fixation cross at the start of each trial. Double click on the first text display and simply type a plus sign (+) in the text box. Click on the property pages icon in the top corner of the box in the workspace and click on the duration tab (see Step 2). Alter the duration to 500. This means that the fixation cross will appear for half a second.
Now open the second text display in the workspace. This text display will be used to display the stimuli. In the text box type [stimulus]. Adding the square brackets means that e-prime will access the text from the list (i.e. it will present ‘Tiger’, ‘Horse’, ‘Table’ or ‘Chair’ depending on what row of the list e-prime is accessing). Click on the property pages and select duration:
Now double click on the feedback display item in the structure window to open it up in the workspace:
Step 5. Test your experiment. You are now half way through the experiment. Test it to see if it works. Click on the purple running man on the top tool bar to test your experiment. Running the experiment automatically saves it. If you have not saved it already, if may ask you to do so.
Step 6. Adding a picture block. E-prime presents bitmaps at 800x600 pixels resolution. I have saved some example pictures into the folder class_share>training folder. This is the directory where you should save your version of this experiment before adding the pictures. The easiest way for e-prime to present pictures is if the bitmaps and the experiment are saved in the same folder.
Step 7. Randomising the blocks. When you test your experiment you will see that the trials come up in the same order every time. This is because the trials are in sequential order. You can randomise any list by double clicking on the list icon in the structure window and then clicking on the property pages icon.
Then click on the Selection tab, and open the Order drop down menu. A variety of options can be selected.
Step 8. Looking at the data. Under the tools menu on e-prime you can open E-DataAid. This software allows you to look at the data. When the software opens you need to open your data file which will be saved in the same folder as the experiment. When open it will look like this:
Most of the columns will not interest you. The columns that you need to check refer to your subject’s accuracy and response time. As subjects responded to the stimuli during textdisplay3 then the columns textdisplay3.acc and textdisplay3.rt provide the accuracy and response times. Find the accuracy column and double click on the column header.
Now close the filter box after clicking OK, and return to the datasheet. Next click on the calculator icon on the top tool bar. This brings up the analysis box:
Further Exercises:
1. Create a third procedure that uses both the word and picture (using a ‘slide’ object)
2. Create a procedure that uses nested lists. If, for example, you wanted the program to pick a random stimulus within a category (i.e. randomly pick an animal) without going through the whole procedure list, then you need to create two nested lists called ‘animals’ and ‘furniture’.
3. Hemifield effects can be studied by presenting the pictures and words either to the left or right of the fixation cross. How can you achieve this?
4. Some research requires an auditory feedback. Try to insert an auditory tone in the feedback object.
This is the tool box where text displays, feedback etc. can be selected.
This is the structure window. This contains a hierarchical description of your experiment
These are the Properties of whatever object you have selected in the structure window
This is the workspace. Selecting an object in the structure window brings up a representation in the workspace for you to work upon.
Change the back colour to black and the fore colour to white (or colours of your choice).
Then click on the duration tab
The duration of the stimulus can be set to anything in ms. In this instance we want it to be dependant on the subject pressing a button. In these cases you should put –1 in the duration box. If you wanted it to last for a second, you would put 1000.
Click on the ‘add’ button to add a response. Choose keyboard.
The default is {ANY} button, but if you wanted to be more specific you would type {SPACE}. Normal alphanumeric keys are entered into this box without parentheses.
The list opens with only one row. Add another row by clicking the ‘add row’ button.
In the Procedure column type ‘wordblock’ for one row and ‘imageblock’ for the second row.
Notice that two new procedures have now appeared in the structure window. Now double click on the first procedure to open up the line in the workspace. Drag your second list icon from the toolbox and place it on this line. Double click on this second list icon to open it up in the workspace.
In this new list you first need to add three extra rows and two extra columns using the buttons at the top of the window.
Each row is a trial. The ‘weight’ reflects how many times the trial is run in that experiment. For this experiment change the weight to 3 for each row. This results in 12 trials for this block.
Type ‘wordproc’ in the Procedure column for each row.
Name the first extra column ‘Stimulus’. This is where you tell the computer what to present. Type Tiger, Horse, Chair and Table in the four rows of this column.
Name the second column ‘CorrectAnswer’. The first two rows should be Z and the last two rows should be M (small letters – not capitals).
a). Change the duration to –1. The stimulus will be presented until the subject makes a response.
b). Add a keyboard response
c). The allowable keys that subjects can press are Z and M. Both should be entered here.
d). In order to give the subject feedback e-prime needs to know what the correct answer is. Here, you can tell the computer that the correct answer can be found in the list. Enter [correctanswer] and e-prime will check the appropriate column.
e). Make sure that data logging is set to standard, otherwise e-prime will not record whether the subject was correct or not.
a)
b)
c)
d)
e)
Ensure that the Feedbackdisplay1 is selected.
Click on the property pages icon.
In the Input Object Name slot you need to enter the name of the object to which you want to attach feedback (i.e. the one they respond to). The drop down menu shows you what’s available. If you haven’t changed the names of any of the objects in the structure window, then the entry should be TextDisplay3.
Drag another list icon from the toolbox onto the imageblock procedure line in the structure window. Double click to open it. The list should be filled in exactly the same as the wordblock list, except that the procedure should be called ‘imageproc’ and under the stimulus column you type the names of the bitmaps. The names are ‘tiger.bmp’, ‘horse.bmp’, ‘chair.bmp’, and ‘table.bmp’.
Next, double click the new ‘imageproc’ and drag a test display, an image display and a feedback display onto the procedure line. The text display should have a fixation cross (+) added to it and be set to 500 ms. The feedback display should be set to take input from imagedisplay1 in the same way that you did for the wordproc.
Double click on imagedisplay1 icon in the structure window and open the property pages. On the General page type [stimulus] into the filename. Again, the square brackets mean that e-prime knows to look for the image in the stimulus column in the list.
The filter box should appear. Click on checklist.
Then click on 1. This will hide all incorrect responses and not include them in any summary statistics.
Drag textdisplay3.RT:mean into the data box. Click run and you will be given the mean response time for correct answers while categorising words. The same procedure can be repeated for the responses to the images to produce the overall mean response time to pictures. In fact both means can be produced at the same time but unfortunately we do not have enough time to go into the subtleties of DataAid.
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