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:

Sample Visual Search Stimulus

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

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.

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 undefined Path to image file that is the foil/distractor.
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 numeric 74 The key to press if the target is present in the search array.
target_absent_key numeric 70 The key to press if the the target is not present in the search array.
timing_max_search numeric -1 The maximum amount of time the subject is allowed to search before the trial will continue. A value of -1 will allow the subject to search indefinitely.
timing_fixation 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.
key_press numeric Indicates which key the subject pressed. The value is the numeric key code corresponding to the subject's response.
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 JSON string JSON-encoded array where each element of the array 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.

Example