This plugin displays and image and records responses generated with the keyboard.The stimulus can be displayed until a response is given, or for a pre-determined amount of time. The trial can be ended automatically if the subject has failed to respond within a fixed length of time.


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 of the image file to be displayed.
choices array of keycodes jsPsych.ALL_KEYS This array contains the keys that the subject is allowed to press in order to respond to the stimulus. Keys can be specified as their numeric key code or as characters (e.g., 'a', 'q'). The default value of jsPsych.ALL_KEYS means that all keys will be accepted as valid responses. Specifying jsPsych.NO_KEYS will mean that no responses are allowed.
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 timing_response parameter). If false, then the trial will continue until the value for trial_duration is reached. You can use this parameter to force the subject to view a stimulus for a fixed amount of time, even if they respond before the time is complete.

Data Generated

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

Name Type Value
key_press numeric Indicates which key the subject pressed. The value is the numeric key code corresponding to the subject's response.
rt numeric The response 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.


Displaying trial until subject gives a response

var trial = {
    type: 'image-keyboard-response',
    stimulus: 'img/happy_face_1.png',
    choices: ['e', 'i'],
    prompt: "<p>Is this person happy or sad? Press 'e' for happy and 'i' for sad.</p>",
  response_ends_trial: false

Displaying image for a fixed duration; no response allowed

var trial = {
    type: 'image-button-response',
    stimulus: 'img/happy_face_1.png',
    choices: jsPsych.NO_KEYS,
    prompt: "<p>Study this face for 5 seconds.</p>",
    trial_duration: 5000