trial_video_button_response function is used to play
a video stimulus and collect a response using on screen buttons.
trial_video_button_response( sources, trial_ends_after_video = FALSE, width = NULL, height = NULL, autoplay = TRUE, controls = FALSE, start = NULL, stop = NULL, rate = 1, choices = c("button 0", "button 1", "button 2"), button_html = NULL, margin_vertical = "0px", margin_horizontal = "8px", prompt = NULL, trial_duration = NULL, response_ends_trial = TRUE, post_trial_gap = 0, on_finish = NULL, on_load = NULL, data = NULL )
Path(s) to the video file. Videos may be specified in multiple formats (e.g., .mp4, .ogg, .webm)
If TRUE the trial will end as soon as the video finishes playing.
The width of the video display in pixels (if NULL, natural width is used)
The height of the video display in pixels (if NULL, natural height is used)
Does the video play automatically?
Should the video controls be shown?
Time point in seconds to start video (NULL starts at the beginning)
Time point in seconds to stop video (NULL stops at the end)
What rate to play the video (1 = normal, <1 slower, >1 faster)
Labels for the buttons. Each element of the character vector will generate a different button.
A template of HTML for generating the button elements (see details)
Vertical margin of the buttons
Horizontal margin of the buttons
A string (may contain HTML) that will be displayed below the stimulus, intended as a reminder about the actions to take (e.g., which key to press).
How long to wait for a response before ending trial in milliseconds. If NULL, the trial will wait indefinitely. If no response is made before the deadline is reached, the response will be recorded as NULL.
If TRUE, then the trial will end when a response is made (or the trial_duration expires). If FALSE, the trial continues until the deadline expires.
The gap in milliseconds between the current trial and the next trial. If NULL, there will be no gap.
An object containing additional data to store for the trial
Functions with a
trial_ prefix always return a "trial" object.
A trial object is simply a list containing the input arguments, with
NULL elements removed. Logical values in the input (
FALSE) are transformed to character vectors
and are specified to be objects of class "json", ensuring that they will be
trial_video_button_response function belongs to the "stimulus-response"
family of trials, all of which display a stimulus of a particular type (image,
audio, video or HTML) and collect responses using a particular mechanism
(button, keyboard or slider).
This one plays a video and records responses generated with a button click.
The response buttons can be customized using HTML formatting, via the
This argument allows the user to specify an HTML used to generating the button elements. If this
argument is a vector of the same length as
choices then the i-th element of
will be used to define the i-th response button. If
button_html is a single string then the
same template will be applied to every button. The templating is defined using a special string
"%choice%" that will be replaced by the corresponding element of the
choices vector. By default
the jsPsych library creates an HTML button of class "jspsych-btn" and the styling is governed by the
Depending on parameter settings, the trial can end when the subject responds
response_ends_trial = TRUE), or after a fixed amount of time
(specified using the
trial_duration argument) has elapsed. The trial can
also be made to end automatically at the end of the video using the
Like all functions in the
trial_ family it contains four additional
post_trial_gap argument is a numeric value specifying the
length of the pause between the current trial ending and the next one
beginning. This parameter overrides any default values defined using the
build_experiment function, and a blank screen is displayed
during this gap period.
on_finish arguments can be used to
fn_ family of functions supplies a variety of functions that may
be useful in many cases.
data argument can be used to insert custom data values into
the jsPsych data storage for this trial
When this function is called from R it returns the trial object that will
later be inserted into the experiment when
is called. However, when the trial runs as part of the experiment it returns
values that are recorded in the jsPsych data store and eventually form part
of the data set for the experiment.
The data recorded by this trial is as follows:
rt value is the response time in milliseconds taken for the
user to make a response. The time is measured from when the stimulus first
appears on the screen until the response.
button_pressed variable is a numeric value indicating which
button was pressed. The first button in the choices array is recorded as
value 0, the second is value 1, and so on.
stimulus variable records a JSON encoding of the sources array.
In addition, it records default variables that are recorded by all trials:
trial_type is a string that records the name of the plugin used to run the trial.
trial_index is a number that records the index of the current trial across the whole experiment.
time_elapsed counts the number of milliseconds since the start of the experiment when the trial ended.
internal_node_id is a string identifier for the current "node" in the timeline.
Within the "stimulus-response" family of trials, there are four types of
stimuli (image, audio, video and HTML) and three types of response options
(button, keyboard, slider). The corresponding functions are