The program INHIB runs an attentional cueing experiment under conditions in which subjects should be slower to detect a stimulus presented at a previously cued location. Such a phenomenon has been called "inhibition of return" because subjects appear to be inhibited in returning their attention to the previously attended, but then unattended location. On each trial, one of two peripheral boxes flashes, the central fixation symbol flashes, and then an 'X' is presented in one of the peripheral boxes. The subject must press a single key (the space bar is good) as soon as the target 'X' is detected. The key should be pressed as quickly as possible. The subject can ignore the initial cue (the flashing box) because it does not predict the subsequent target location. That is, the cue is VALID on half of the trials, and INVALID on the other half. Furthermore, because the cue is uninformative, the subject should remain fixated on the central fixation point throughout the trial.
In addition to valid and invalid trials there are also a number of trials without any X presented at all. On these catch trials the subject should be sure to not press the response key.
If the response was incorrect, or if no key was pressed, a short tone is presented. Raw data from the experiment are
placed in the file DINHIB.DAT. An analysis program (INHIBANAL) 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 AINHIB.ANL.
Running the experiment
To run the experiment, type INHIB 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 begin the first trial immediately. The parameters that can be safely changed are listed below, along with their probable default values.
1. Total number of non catch-trials per block (must be multiple of 4):
(default=40)
2. Total number of blocks per session:
(default=6)
3. Number of catch trials per block (must be mult of 4):
(default=8)
4. Number of practice blocks:
(default=1)
5. Inter-trial interval (msec):
(default=500)
6. Duration of error tone (msec):
(default=500)
7. Interval between display onset and cue (msec):
(default=1000)
8. Interval between cue and center flash (msec):
(default=200)
9. Interval between center flash and target (msec):
(default=200)
10. x location of stimuli
(default=16000)
11. y location of fixation point
(default=16000)
12. Color of target X (white, red, green, blue, yellow):
(default=1)
15. Minimum allowed RT (msec):
(default=100)
16. Distance between fixation and stimuli (video units):
(default=8000)
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=3000)
Note. The order of conditions within a block, and the locations of the stimuli are determined randomly.
Analyzing the data (You will need analysis program available below)
Simply type INHIBANA 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 AINHIB.ANL (i.e., issue the command: TYPE AINHIB.ANL
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