Donders reaction time experiment
Overview. The Donders.psyexp program runs an experiment that includes the three types of reactions identified byDonders (1 Stimulus (S) 1 Response (R); 2S2R; 2S1R). Conditions are run in separate blocks with instructions presented at the beginning of each block. Subjects respond by pressing one of two keys when the target (an ‘X’) is detected.
Details. Run the program by double-clicking on the Donders.psyexp file. This will launch PsychoPy with the experiment timeline loaded. Run the experiment by selecting “run” from the PsychoPy menu (the green running person). A dialog box will appear in which the student can optionally enter their name or initials. Any string entered will become the first part of the name of the data file.
On each trial two boxes will appear (one on each side of fixation), and then a short time later the letter X will be presented in one of the boxes. The correct response depends upon the block instructions. Subjects respond by using the z and / keys. The program begins with a short practice block in each condition. Practice is followed by 9 test blocks (three of each type of reaction). Blocks in the 2S2R condition have 20 trials. Blocks in 1S1R have 10 trials. Blocks in 2S1R present 20 trials but require responses on only 10 of them.
Other details of the method can be learned by examining the timeline and the events in PsychoPy. In cases where attributes of the events are variable, the variables are typically specified in the provided Excel files.
Data analysis. The data are in a *.CSV file in the “data” folder in the Psych/Lab folder. Double-click on this file to open it in Excel. Each row corresponds to a trial. Entries in the column labeled condition show the condition for that trial. Keyresponse.RT contains the reaction time (in seconds). Keyresponse.corr codes whether the response was correct (1) or incorrect (0). The first one (or more) sets of trials might be practice and should not be analyzed. See the instructions elsewhere for creating a pivot table to summarize the data.