categorize-image

The categorize image plugin shows an image object on the screen. The subject responds by pressing a key. Feedback indicating the correctness of the response is given.

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.
key_answer	string	undefined	The key character indicating the correct response.
choices	array of strings	"ALL_KEYS"	This array contains the key(s) that the subject is allowed to press in order to respond to the stimulus. Keys should be specified as characters (e.g., 'a', 'q', ' ', 'Enter', 'ArrowDown') - see this page and this page (event.key column) for more examples. Any key presses that are not listed in the array will be ignored. The default value of "ALL_KEYS" means that all keys will be accepted as valid responses. Specifying "NO_KEYS" will mean that no responses are allowed.
text_answer	string	""	A label that is associated with the correct answer. Used in conjunction with the correct_text and incorrect_text parameters.
correct_text	string	"Correct."	String to show when the correct answer is given. Can contain HTML formatting. The special string %ANS% can be used within the string. If present, the plugin will put the text_answer for the trial in place of the %ANS% string (see example below).
incorrect_text	string	"Wrong."	String to show when the wrong answer is given. Can contain HTML formatting. The special string %ANS% can be used within the string. If present, the plugin will put the text_answer for the trial in place of the %ANS% string (see example below).
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).
force_correct_button_press	boolean	false	If set to true, then the subject must press the correct response key after feedback is given in order to advance to the next trial.
show_stim_with_feedback	boolean	true	If set to true, then the stimulus will be shown during feedback. If false, then only the text feedback will display during feedback.
show_feedback_on_timeout	boolean	false	If true, then category feedback will be displayed for an incorrect response after a timeout (trial_duration is exceeded). If false, then a timeout message will be shown.
timeout_message	string	"Please respond faster."	The message to show on a timeout non-response.
stimulus_duration	numeric	null	How long to show the stimulus for (milliseconds). If null, then the stimulus is shown until a response is given.
feedback_duration	numeric	2000	How long to show the feedback for (milliseconds).
trial_duration	numeric	null	The maximum time allowed for a response. If null, then the experiment will wait indefinitely for a response.

Data Generated

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

Name	Type	Value
stimulus	string	Either the path to the image file or the string containing the HTML formatted content that the subject saw on this trial.
response	string	Indicates which key the subject pressed.
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.
correct	boolean	true if the subject got the correct answer, false otherwise.

Examples

Categorizing an image

Code

var categorization_trial = {
    type: jsPsychCategorizeImage,
    stimulus: 'img/blue.png',
    key_answer: 'b',
    text_answer: 'Blue',
    choices: ['r', 'g', 'b'],
    correct_text: "<p class='prompt'>Correct! The color is %ANS%.</p>",
    incorrect_text: "<p class='prompt'>Incorrect. The color is %ANS%.</p>",
    prompt: "<p>Is the color of this circle (R)ed, (G)reen, or (B)lue?</p>"
};

Demo

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