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jspsych-vsl-animate-occlusion plugin

The VSL (visual statistical learning) animate occlusion plugin displays an animated sequence of shapes that disappear behind an occluding rectangle while they change from one shape to another. This plugin can be used to replicate the experiments described in:

Fiser, J., & Aslin, R. N. (2002). Statistical learning of higher-order temporal structure from visual shape sequences. Journal of Experimental Psychology: Learning, Memory, and Cognition, 28(3), 458.

Dependency

This plugin requires the Snap.svg library, available at http://www.snapsvg.io. You must include the library in the <head> section of your experiment page.

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
stimuli array undefined Each element of the array is a stimulus. A stimulus is a path to an image file. The order of stimuli in the array determines the order of the animation sequence.
canvas_size array [400, 400] Array specifying the width and height of the area that the animation will display in. Stimuli will move to the edges of this area, so increasing the width without increasing the timing_cycle parameter will speed up the images.
image_size array [100, 100] Array specifying the width and height of the images to show. The occluding rectangle will have a width equal to the width of image_size.
initial_direction string "left" Which direction the stimulus should move first (subsequent directions will alternate). Choices are "left" or "right".
occlude_center boolean true If true, display a rectangle in the center of the screen that is just wide enough to occlude the image completely as it passes behind.
choices array of strings jsPsych.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 jsPsych.ALL_KEYS means that all keys will be accepted as valid responses. Specifying jsPsych.NO_KEYS will mean that no responses are allowed.
cycle_duration numeric 1000 How long it takes for a stimulus in the sequence to make a complete cycle (move to the edge and back to the center) in milliseconds.
pre_movement_duration numeric 500 How long to wait before the stimuli starts moving from behind the center rectangle.

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 array Array where each element is a stimulus from the sequence, in the order that they were shown. This will be encoded as a JSON string when data is saved using the .json() or .csv() functions.
response array Array containing all response information. Each element in the array is an object representing each valid response. Each response item has three properties: key the key that was pressed, stimulus the index of the stimulus that was displayed when the response was made, and rt the response time measured since the start of the sequence. This will be encoded as a JSON string when data is saved using the .json() or .csv() functions.

Examples

Displaying a simple sequence.

var trial = {
  type: 'vsl-animate-occlusion',
  stimuli: [
    "img/1.gif",
    "img/2.gif",
    "img/3.gif",
    "img/4.gif",
    "img/5.gif",
    "img/6.gif",
    "img/7.gif",
    "img/8.gif",
    "img/9.gif",
    "img/10.gif"
  ]
}