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53 lines
3.8 KiB
Markdown
53 lines
3.8 KiB
Markdown
# jspsych-xab plugin
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The XAB plugin displays either an image or HTML object stimulus (X). After a short gap, the plugin displays two additional stimuli (A and B). The subject selects which of the two stimuli matches X using the keyboard.
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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* | Array of arrays. Each interior array represents the stimuli for a single trial. Each interior array can be two or three elements. If it is two elements, then the plugin will show the first element as X and as the target during the A/B portion (the second element will be the foil). If it is three elements, then the first is X the second is the target (A) and the third is the foil (B). This is useful if X and A are not identical, but A is still the correct choice (e.g. a categorization experiment where the goal is to pick the item that is in the same category). Stimuli can be paths to images, or html strings.
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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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left_key | numeric or string | 'Q' | Which key the subject should press to indicate that the target is on the left side.
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right_key | numeric or string | 'P' | Which key the subject should press to indicate that the target is on the right side.
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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_x | numeric | 1000 | How long to show the X stimulus for in milliseconds.
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timing_xab_gap | numeric | 1000 | How long to show a blank screen in between X and AB in milliseconds.
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timing_ab | numeric | -1 | How long to show A and B in milliseconds. If the value of this parameter is -1, then the stimuli will remain on the screen until a response is given.
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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_x | string | Either the path to the image file or the string containing the HTML formatted content that was the X stimulus on this trial.
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stimulus_a | string | Either the path to the image file or the string containing the HTML formatted content that was the A stimulus on this trial.
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stimulus_b | string | Either the path to the image file or the string containing the HTML formatted content that was the B stimulus 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 A and B stimuli first appear on the screen until the subject's response.
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correct | boolean | True if the subject picks the correct answer.
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## Examples
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#### Doing an exact match task
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```javascript
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var block = {
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type: 'xab',
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stimuli: [['img/happy_face.png', 'img/sad_face.png']],
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prompt: "Press Q if the face you just saw is on the left. Press P if the face you just saw is on the right."
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}
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```
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#### Matching based on a feature
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```javascript
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var block = {
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type: 'xab',
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stimuli: [['img/happy_joe_face.png', 'img/sad_joe_face.png', 'img/sad_fred_face.png']],
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prompt: "Press Q if the person you just saw is on the left. Press P if the person you just saw is on the right."
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}
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``` |