Data Variables

In the previous example, we created a derived parameter that determined the correct key based on the color of the Stroop stimulus. We can now create a data variable that determines whether the participant pressed the correct key. We can then use this data variable to create feedback for the participant.

Assume the same timeline as before and the same derived parameter:

from sweetbean.parameter import (
    DataVariable,
    DerivedLevel,
    DerivedParameter,
    TimelineVariable,
)
from sweetbean.sequence import Block, Experiment
from sweetbean.stimulus import TextStimulus

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

# EVENT SEQUENCE

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


def is_correct_f(color):
    return color == "red"


def is_correct_j(color):
    return not is_correct_f(color)


j_key = DerivedLevel("j", is_correct_j, [color])
f_key = DerivedLevel("f", is_correct_f, [color])

correct_key = DerivedParameter("correct", [j_key, f_key])

Now we can create a DataVariable that determines whether the participant pressed the correct key, specified by the correct keyword. This keyword indicates a special data point which can be accessed in stimuli that have the correct_key parameter. A comprehensive list of data points that can be accessed will be made available in the documentation (It is mainly the data that gets stored via jsPsych.

The 1 in the declaration below indicates from which stimulus to get the variable (1 = previous, 2 = second previous, etc.).

correct = DataVariable("correct", [True, False])

# Predicates
def is_correct(correct):
    return correct


def is_false(correct):
    return not correct


correct_feedback = DerivedLevel("correct", is_correct, [correct], 1)
false_feedback = DerivedLevel("false", is_false, [correct], 1)

Again, we can use the Derived Levels to create a Derived Parameter and use it in a feedback stimulus.

feedback_text = DerivedParameter("feedback_text", [correct_feedback, false_feedback])

fixation = FixationStimulus(500)
stroop = TextStimulus(2000, word, color, ["j", "f"], correct_key)
feedback = TextStimulus(800, feedback_text)

event_sequence = [fixation, stroop, feedback]


train_block = Block(event_sequence, timeline)
experiment = Experiment([train_block])

experiment.to_html("stroop.html")