I am new to Psychopy, I have a question about inserting a jitter for a fixation point. It is important to note that while the fixation point must be jittered, there are a fixed number of presentation times that must be used. For example, if there are 5 trials in a block, the fixation presentation time would need to be randomly chosen from a list of 5 times (2s, 2.5s, 3s, 3.5s, 4s). These would be exactly the same for each participant, but the order would be random.
In this experiment, each trial looks like this: Fixation (text file) -> Image with a response required -> wait -> Fixation… and so on.
Suppose the Excel file guiding the block of trials looks like this:
Fixation Image CorrectResponse
2.0 A left
2.5 B right
3.0 C left
3.5 D right
4.0 E left
The values in the fixation column are times in seconds. In the Builder view, the duration of the fixation point (which is a text object) is set to $Fixation. Doing this causes problems because Image A will always have a 2 second fixation preceding it, Image B a 2.5 second fixation preceding it, and so on.
I want the routine to randomly choose a value from the Fixation column for each fixation duration, while keeping the Image/Correct Response columns tied to each other (but still chosen independently from the Fixation column). I am certain I will need to do this in Coder view, but am unsure how to do it. Any help would be appreciated. Thank you.