R/trial_image_keyboard_response.R

In djnavarro/jaysire: Build jsPsych Experiments in R

#' Specify an image trial with keyboard response
#'
#' @description The \code{trial_image_keyboard_response} function is used to display
#' an image stimulus and collect a response using a key press.
#'
#' @param stimulus The path of the image file to be displayed.
#' @param stimulus_height Set the height of the image in pixels. If NULL, then the image will display at its natural height.
#' @param stimulus_width Set the width of the image in pixels. If NULL, then the image will display at its natural width.
#' @param maintain_aspect_ratio If setting only the width or only the height and this parameter is TRUE, then the other dimension will be scaled to maintain the image's aspect ratio.
#'
#' @param choices A character vector of keycodes (either numeric values or the characters themselves). Alternatively, respond_any_key() and respond_no_key() can be used
#'
#' @param prompt 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).
#' @param stimulus_duration How long to show the stimulus, in milliseconds. If NULL, then the stimulus will be shown until the subject makes a response
#' @param trial_duration 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.
#' @param response_ends_trial 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.
#'
#' @param post_trial_gap  The gap in milliseconds between the current trial and the next trial. If NULL, there will be no gap.
#' @param on_finish A javascript callback function to execute when the trial finishes
#' @param on_load A javascript callback function to execute when the trial begins, before any loading has occurred
#' @param data An object containing additional data to store for the trial
#'
#' @return Functions with a \code{trial_} prefix always return a "trial" object.
#' A trial object is simply a list containing the input arguments, with
#' \code{NULL} elements removed. Logical values in the input (\code{TRUE} and
#' \code{FALSE}) are transformed to character vectors \code{"true"} and \code{"false"}
#' and are specified to be objects of class "json", ensuring that they will be
#' written to file as the javascript logicals, \code{true} and \code{false}.
#'
#' @details The \code{trial_image_keyboard_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 displays an image and records responses generated with a key press.
#'
#' \subsection{Stimulus display}{
#' For trials that display an image, the \code{stimulus} argument is a string that
#' specifies the path to the image file. More precisely, it must specify the path to
#' where the image file will be located at the time the experiment runs. Typically,
#' if an experiment is deployed using the \code{\link{build_experiment}()} function
#' all resource files will be stored in a "resource" folder, and the images will
#' be copied to the "image" subfolder. So if the image to be displayed is a file
#' called "picture.png", the \code{stimulus} path on a Mac or Linux machine would
#' likely be "resource/image/picture.png". Note that this path is specified relative
#' to the location of the primary experiment file "image.html". To make this a little
#' easier, the \code{\link{insert_resource}()} function can be used to construct
#' resource paths automatically. In the example above,
#' \code{stimulus = insert_resource("picture.png")} would suffice.
#'
#'
#' Other aspects to the stimulus display can be controlled with other arguments.
#' The \code{stimulus_height} and \code{stimulus_width} arguments can be used to
#' manually control the image display size by specifying the height/width in
#' pixels. If only one of these two arguments is specified, but the
#' \code{maintain_aspect_ratio} value is set to \code{TRUE}, the other dimension
#' of the image will automatically be scaled appropriately.
#'
#'
#' The length of time that the image remains on screen can also be customised
#' by setting the \code{stimulus_duration} argument: this should be a numeric
#' value indicating the number of milliseconds before the image disappears.
#' Alternatively, a value of \code{NULL} (the default) ensures that the image
#' remains visible until the trial ends.
#' }
#'
#' \subsection{Response mechanism}{
#' For this kind of trial, participants can make a response by pressing a key,
#' and the \code{choices} argument is used to control which keys will register
#' a valid response. The default value \code{choices = \link{respond_any_key}()}
#' is to allow the participant to press any key to register their response.
#' Alternatively it is possible to set \code{choices = \link{respond_no_key}()},
#' which prevents all keys from registering a response: this can be useful if
#' the trial is designed to run for a fixed duration, regardless of what the
#' participant presses.
#'
#' In many situations it is preferable to require the participant to respond
#' using specific keys (e.g., for a binary choice tasks, it may be desirable to
#' require participants to press F for one response or J for the other). This
#' can be achieved in two ways. One possibility is to use a character vector
#' as input (e.g., \code{choices = c("f","j")}). The other is to use the
#' numeric code that specifies the desired key in javascript, which in this
#' case would be \code{choices = c(70, 74)}. To make it a little easier to
#' work with numeric codes, the jaysire package includes the
#' \code{\link{keycode}()} function to make it easier to convert from one format
#' to the other.
#' }
#'
#' \subsection{Other behaviour}{
#' Depending on parameter settings, the trial can end when the subject responds
#' (\code{response_ends_trial = TRUE}), or after a fixed amount of time
#' (specified using the \code{trial_duration} argument) has elapsed. The length
#' of time that the stimulus remains visible can also be customized using the
#' (\code{stimulus_duration}) argument.
#'
#' Like all functions in the \code{trial_} family it contains four additional
#' arguments:
#'
#' \itemize{
#' \item The \code{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
#' \code{\link{build_experiment}} function, and a blank screen is displayed
#' during this gap period.
#'
#' \item The \code{on_load} and \code{on_finish} arguments can be used to
#' specify javascript functions that will execute before the trial begins or
#' after it ends. The javascript code can be written manually and inserted *as*
#' javascript by using the \code{\link{insert_javascript}} function. However,
#' the \code{fn_} family of functions supplies a variety of functions that may
#' be useful in many cases.
#'
#' \item The \code{data} argument can be used to insert custom data values into
#' the jsPsych data storage for this trial.
#' }
#' }
#'
#' \subsection{Data}{
#'
#' When this function is called from R it returns the trial object that will
#' later be inserted into the experiment when \code{\link{build_experiment}}
#' 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:
#'
#' \itemize{
#' \item The \code{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.
#' \item The \code{key_press} variable is the numeric javascript key code
#' corresponding to the response.
#' \item The \code{stimulus} variable records the path to the image that was
#' displayed on this trial.
#'}
#'
#' In addition, it records default variables that are recorded by all trials:
#'
#' \itemize{
#' \item \code{trial_type} is a string that records the name of the plugin used to run the trial.
#' \item \code{trial_index} is a number that records the index of the current trial across the whole experiment.
#' \item \code{time_elapsed} counts the number of milliseconds since the start of the experiment when the trial ended.
#' \item \code{internal_node_id} is a string identifier for the current "node" in the timeline.
#' }
#' }
#'
#' @seealso 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
#' \code{\link{trial_image_button_response}},
#' \code{\link{trial_image_keyboard_response}},
#' \code{\link{trial_image_slider_response}},
#' \code{\link{trial_audio_button_response}},
#' \code{\link{trial_audio_keyboard_response}},
#' \code{\link{trial_audio_slider_response}},
#' \code{\link{trial_video_button_response}},
#' \code{\link{trial_video_keyboard_response}},
#' \code{\link{trial_video_slider_response}},
#' \code{\link{trial_html_button_response}},
#' \code{\link{trial_html_keyboard_response}} and
#' \code{\link{trial_html_slider_response}}.
#'
#' @export
trial_image_keyboard_response <- function(
  stimulus,
  stimulus_height = NULL,
  stimulus_width = NULL,
  maintain_aspect_ratio = TRUE,

  choices = respond_any_key(),

  prompt = NULL,
  stimulus_duration = NULL,
  trial_duration = NULL,
  response_ends_trial = TRUE,

  post_trial_gap = 0,  # start universals
  on_finish = NULL,
  on_load = NULL,
  data = NULL
) {
  drop_nulls(
    trial(
      type = "image-keyboard-response",
      stimulus = stimulus,
      stimulus_height = stimulus_height,
      stimulus_width = stimulus_width,
      maintain_aspect_ratio = js_logical(maintain_aspect_ratio),

      choices = choices,

      prompt = prompt,
      stimulus_duration = stimulus_duration,
      trial_duration = trial_duration,
      response_ends_trial = js_logical(response_ends_trial),

      post_trial_gap = post_trial_gap,
      on_finish = on_finish,
      on_load = on_load,
      data = data
    )
  )
}