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jspsych-image-slider-response

This plugin displays and image and allows the subject to respond by dragging a slider.

Image files can be automatically preloaded by jsPsych using the preload plugin. However, if you are using timeline variables or another dynamic method to specify the image stimulus, you will need to manually preload the images.

Parameters

In addition to the parameters available in all plugins, this plugin accepts the following parameters. Parameters with a default value of undefined must be specified. Other parameters can be left unspecified if the default value is acceptable.

Parameter Type Default Value Description
stimulus string undefined The path to the image file to be displayed.
stimulus_height integer null Set the height of the image in pixels. If left null (no value specified), then the image will display at its natural height.
stimulus_width integer null Set the width of the image in pixels. If left null (no value specified), then the image will display at its natural width.
maintain_aspect_ration boolean true 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.
labels array of strings [] Labels displayed at equidistant locations on the slider. For example, two labels will be placed at the ends of the slider. Three labels would place two at the ends and one in the middle. Four will place two at the ends, and the other two will be at 33% and 67% of the slider width.
button_label string 'Continue' Label of the button to advance/submit
min integer 0 Sets the minimum value of the slider
max integer 100 Sets the maximum value of the slider
slider_start integer 50 Sets the starting value of the slider
step integer 1 Sets the step of the slider
slider_width integer null Set the width of the slider in pixels. If left null, then the width will be equal to the widest element in the display.
require_movement boolean false If true, the subject must move the slider before clicking the continue button.
prompt string null This string can contain HTML markup. Any content here will be displayed below the stimulus. The intention is that it can be used to provide a reminder about the action the subject is supposed to take (e.g., which key to press).
stimulus_duration numeric null How long to show the stimulus for in milliseconds. If the value is null, then the stimulus will be shown until the subject makes a response.
trial_duration numeric null How long to wait for the subject to make a response before ending the trial in milliseconds. If the subject fails to make a response before this timer is reached, the subject's response will be recorded as null for the trial and the trial will end. If the value of this parameter is null, then the trial will wait for a response indefinitely.
response_ends_trial boolean true If true, then the trial will end whenever the subject makes a response (assuming they make their response before the cutoff specified by the trial_duration parameter). If false, then the trial will continue until the value for trial_duration is reached. You can set this parameter to false to force the subject to view a stimulus for a fixed amount of time, even if they respond before the time is complete.
render_on_canvas boolean true If true, the image will be drawn onto a canvas element. This prevents a blank screen (white flash) between consecutive image trials in some browsers, like Firefox and Edge. If false, the image will be shown via an img element, as in previous versions of jsPsych. If the stimulus is an animated gif, you must set this parameter to false, because the canvas rendering method will only present static images.

Data Generated

In addition to the default data collected by all plugins, this plugin collects the following data for each trial.

Name Type Value
response numeric The numeric value of the slider.
rt numeric The time in milliseconds for the subject to make a response. The time is measured from when the stimulus first appears on the screen until the subject's response.
stimulus string The path of the image that was displayed.
slider_start numeric The starting value of the slider.

Examples

Displaying trial until subject gives a response

var trial = {
    type: 'image-slider-response',
    stimulus: 'img/happy_face_1.png',
    labels: ['happy', 'sad'],
    prompt: "<p>How happy/sad is this person?</p>",
  response_ends_trial: false
};