Timeline Variables

In the previous examples, we have seen how to create a simple block with a fixed trials. Here, we will introduce timeline variables that can be used to create more complex experiments with multiple trials.

Consider the following timeline that consists of words and colors for a Stroop Task:

timeline = [
    {"color": "red", "word": 'RED'},
    {"color": "green", "word": "GREEN"},
    {"color": "green", "word": "RED"},
    {"color": "red", "word": "GREEN"},
]

First, we declare SweetBean Timeline Variables:

color: The name has to be color (it is the name in the timeline), and it has the levels red and green word: The name has to be word (it is the name in the timeline), and it has the levels RED and GREEN

from sweetbean.parameter import TimelineVariable

color = TimelineVariable(name="color", levels=["red", "green"])
word = TimelineVariable(name="word", levels=["RED", "GREEN"])

Now, we can use these timeline variables when defining the stimuli:

from sweetbean.stimulus import TextStimulus, FixationStimulus

fixation = FixationStimulus(duration=500)
stroop = TextStimulus(duration=1000, text=word, color=color)

Finally, we can create a block with the timeline. Here, we pass in the timeline to the block. The event sequence will then be repeated as many times as there are entries in the timeline using the variables defined above.

from sweetbean.sequence import Block, Experiment

event_sequence = [fixation, stroop]
stroop_block = Block(event_sequence, timeline)
experiment = Experiment(stroop_block)
experiment.to_html("stroop.html")

Additionally to timeline variables, we can also create derived variables. For example, we can create a variable that gives us the correct key press depending on the word of a StroopStimulus: Derived Variable