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65 lines
4.2 KiB
Markdown
65 lines
4.2 KiB
Markdown
# jspsych-single-stim plugin
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This plugin displays an image or HTML-formatted content and allows the subject to respond by pressing a key on 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.
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Because this plugin can display any HTML content, it is quite versatile. It can be used for any situation in which the response generated by the subject is a single keystroke.
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## Parameters
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This table lists the parameters associated with this plugin. Parameters with a default value of *undefined* must be specified. Other parameters can be left unspecified if the default value is acceptable.
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Parameter | Type | Default Value | Description
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----------|------|---------------|------------
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stimuli | array | *undefined* | Each element of the array is a stimulus. A stimulus can be either a path to an image file or a string containing valid HTML markup. Each stimulus will be presented in its own trial, and thus the length of this array determines the total number of trials.
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is_html | boolean | false | If the elements of the `stimuli` array are strings containing HTML content, then this parameter must be set to true.
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choices | array | [ ] | 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](http://www.cambiaresearch.com/articles/15/javascript-char-codes-key-codes) or as characters (e.g. `'a'`, `'q'`). The default value of an empty array means that all keys will be accepted as valid responses.
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prompt | string | "" | 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).
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timing_stim | numeric | -1 | How long to show the stimulus for in milliseconds. If the value is -1, then the stimulus will be shown until the subject makes a response.
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timing_response | numeric | -1 | 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 the subject's response will be recorded as -1 for the trial and the trial will end. If the value of this parameter is -1, then the trial will wait for a response indefinitely.
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continue_after_response | 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 `timing_response` 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.
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## Data Generated
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In addition to the [default data collected by all plugins](), this plugin collects the following data for each trial.
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Name | Type | Value
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-----|------|------
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stimulus | string | Either the path to the image file or the string containing the HTML formatted content that the subject saw on this trial.
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key_press | numeric | Indicates which key the subject pressed. The value is the [numeric key code](http://www.cambiaresearch.com/articles/15/javascript-char-codes-key-codes) corresponding to the subject's response.
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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.
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## Examples
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These examples show how to define a block using the single-stim plugin to achieve various goals.
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#### Displaying images until subject gives a response
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```javascript
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var block = {
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type: 'single-stim',
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stimuli: ['img/happy_face.png', 'img/sad_face.png']
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}
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```
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#### Restricting which keys the subject can use to respond
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```javascript
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var block = {
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type: 'single-stim',
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stimuli: ['img/happy_face.png', 'img/sad_face.png'],
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choices: ['h','s']
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}
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```
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#### Displaying HTML content for a fixed length of time
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```javascript
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var block = {
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type: 'single-stim',
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stimuli: ['<p>Radio</p>', '<p>Towel</p>', '<p>Match</p>'],
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is_html: true,
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timing_response: 1500,
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continue_after_response: false
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}
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```
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