The program DONDERS runs a reaction time experiment that obtains reaction times in several different conditions. The conditions are those identified by Donders as A, B, and C reactions. On each trial, the subject must press the correct one of two keys in response to the appearance of a 'X' in one of two locations. If the X appears to the left of fixation, the Z key must be pressed; if the X appears to the right of fixation the / key is correct. The correct key should be pressed as quickly as possible. The subject's task, and the possible locations of the stimulus are different in different blocks of trials. In some blocks, the stimulus will appear to the right of fixation on every trial: the subjects is to press the / key as quickly as possible when it appears. In a second type of block, the stimulus could appear to either the left or right of fixation, but the subject need only respond by pressing the / key when the stimulus is on the right. If the stimulus is on the left then no response is required. In the third type of block, the stimulus can appear either to the left or right of fixation and the subject must respond to both possible stimuli: the task is to press the Z or the / key depending on where the stimulus is located. Instructions at the beginning of the block inform the subject as to the condition for that block.
If the response was too slow, incorrect, or if no key was pressed when one was required, a short tone is presented.
Raw data from the experiment are placed in the file DDOND.DAT. An analysis program (DONDANAL) reads the
data file and computes means and standard deviations of the reaction times for correct responses in each of the
conditions. The output of the analysis is placed in the file ADOND.ANL.
Running the experiment
To run the experiment, just type DONDERS and hit "Enter". When asked to "Press any key to
begin", pressing the 'P' key will allow you to change various parameters that determine the design of the experiment
and the timing of trial events. Pressing a key other than 'P' will cause the program to proceed to the instructions for
the first block of trials. The parameters that can be safely changed are listed below, along with their probable default
values.
1. Number of trials per test block:
(default=50)
2. Total number of blocks per session:
(default=9)
3. Number of practice blocks:
(default=3)
4. Number of trials per practice block:
(default=10)
5. Inter-trial interval (msec):
(default=500)
6. Duration of error tone (msec):
(default=500)
10. x location of stimuli (between 0 and 32000):
(default=16000)
11. y location of fixation point:
(default=16000)
12. Color of target X (white, red, green, blue, yellow):
(default=1)
13. Shortest foreperiod (msec):
(default=700)
14. Longest foreperiod (msec):
(default=1100)
15. Minimum allowed RT (msec):
(default=100)
16. Distance between fixation and stimuli (video units):
(default=5000)
17. Width of cue box (video units):
(default=1000)
18. Height of cue box (video units):
(default=1300)
19. Color of boxes (white, red, green, blue, yellow):
(default=5)
20. Maximum allowed RT (msec):
(default=1500)
Analyzing the data (You will need analysis program available below)
Simply type DONDANAL and hit "Enter" from the directory in which the experiment was run. When asked "Number to trim from each end" the user has the option to exclude the desired number of extreme reaction times from the analysis. Hitting "Enter" will not exclude any data. To view the means from each condition TYPE or PRINT the file ADOND.ANL. If you want to view the raw data, TYPE or PRINT the file DDOND.DAT. The conditions in ADOND.ANL will be labeled "1S1R", "2S2R", or "2S1R", where S = stimulus, and R = response. Each time that DONDERS is run, the program will destroy all previous DDOND.DAT data files. Each time that DONDANAL is run, it will destroy all old ADOND.ANL files. Therefore, be sure to look at the data before the experiment is run again.