Psychtoolbox task scripts used to run the VA_RA_PTB study (PTSD veteran decision making under risk and ambiguity, gains and losses)
To run the study:
- Run practice: type in the command RA()
- Run task: type in the command RA(subject ID)
Examine risk and ambiguity attitudes in the monetary gain and loss domains (imaging).
Practice in e-prime; scan in Matlab Psychtoolbox
- 3 risk levels: 0.25, 0.5, 0.75
- 3 ambiguity levels: 0.24, 0.5, 0.74
- 20 amount levels: ±$5, 6, 7, 8, 10, 12, 14, 16, 19, 23, 27, 31, 37, 44, 52, 61, 73, 86, 101, and 120
- Each combination of risk/ambiguity and amount appears once.
- Gain and loss trials are in separate blocks.
- 8 blocks, 31 trials per block.
- 2 orders (gains first or losses first): 2 gains - 2 losses - 2 losses - 2 gains, or 2 losses – 2 gains – 2 gains – 2 losses
- 2 sessions on separate days
Trials are created in the Gain1 and Loss1 scripts (basically the first time you run the subject on this corresponding domain). After creating all trials, the order within each gain/loss domain is permuted, and assigned to 4 blocks, so that each block has 30 trials. Also, we add one other trials at the beginning of each block, which make the total trials per block 31. This trial is always ±$5 vs. a lottery giving ±$4, and will be excluded from analysis. Adding this trial is because the signal is not stable at the beginning when scanner start running.
- options are presented on left and right of screen, 6000ms.
- response cue, and response (< 3500ms)
- feedback image (500ms)
- fixation (jittered 4000, 6000, 8000 ms + (3500ms-response time))
Press one of two buttons.
Real. Subject gets $120 endowment. At the end of the experiment, one trial is randomly selected by rolling a die. Real bags are used as lotteries.