jspsych-visual-search-circle plugin

This plugin presents a customizable visual-search task modelled after Wang, Cavanagh, & Green (1994). The subject indicates whether or not a target is present among a set of distractors. The stimuli are displayed in a circle, evenly-spaced, equidistant from a fixation point. Here is an example using normal and backward Ns:

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
target_present	boolean	undefined	Is the target present?
set_size	numeric	undefined	How many items should be displayed?
target	string	undefined	Path to image file that is the search target.
foil	string or array	undefined	Path to image file that is the foil/distractor. Can specify an array of distractors if the distractors are all different images.
fixation_image	string	undefined	Path to image file that is a fixation target.
target_size	array	[50, 50]	Two element array indicating the height and width of the search array element images.
fixation_size	array	[16, 16]	Two element array indicating the height and width of the fixation image.
circle_diameter	numeric	250	The diameter of the search array circle in pixels.
target_present_key	string	'j'	The key to press if the target is present in the search array.
target_absent_key	string	'f'	The key to press if the target is not present in the search array.
trial_duration	numeric	null	The maximum amount of time the subject is allowed to search before the trial will continue. A value of null will allow the subject to search indefinitely.
fixation_duration	numeric	1000	How long to show the fixation image for before the search array (in milliseconds).

Data Generated

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

Name	Type	Value
correct	boolean	True if the subject gave the correct response.
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.
set_size	numeric	The number of items in the search array
target_present	boolean	True if the target is present in the search array
locations	array	Array where each element is the pixel value of the center of an image in the search array. If the target is present, then the first element will represent the location of the target. This will be encoded as a JSON string when data is saved using the .json() or .csv() functions.

Examples

Identical distractors

Code

var instructions = {
  type: 'html-button-response',
  stimulus: `<p>Press J if there is a backwards N.</p>
    <p>Press F if all the Ns are in the normal orientation.</p>`,
  choices: ['Continue']
}

var trial = {
  type: 'visual-search-circle',
  target: 'img/backwardN.gif',
  foil: 'img/normalN.gif',
  fixation_image: 'img/fixation.gif',
  target_present: true,
  set_size: 4
}

Demo

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Variety of different distractors

Code

var instructions = {
  type: 'html-button-response',
  stimulus: `<p>Press E if there is an elephant in the group.</p>
    <p>Press N if there is no elephant in the group.</p>`,
  choices: ['Continue']
}

var trial = {
  type: 'visual-search-circle',
  target: 'img/elephant.png',
  foil: ['img/lion.png', 'img/monkey.png'],
  fixation_image: 'img/fixation.gif',
  target_present_key: 'e',
  target_absent_key: 'n',
  target_present: true,
  set_size: 3
}

Demo

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