jsPsych/docs/markdown_docs/plugins/jspsych-same-different.md

jspsych-same-different plugin

The same-different plugin displays two stimuli sequentially. Stimuli can be images or HTML objects. The subject responds using the keyboard, and indicates whether the stimuli were the same or different. Same does not necessarily mean identical; a category judgment could be made, for example.

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
stimuli	array	undefined	Each element of the array is a pair of stimuli. Each pair is represented as an array with two entries, one for each stimulus. A stimulus can be either a path to an image file or a string containing valid HTML markup. Stimuli will be shown in the order that they are defined in the array. Each pair will be presented in its own trial, and thus the length of this array determines the total number of trials.
is_html	boolean	false	If the elements of the stimuli array are strings containing HTML content, then this parameter must be set to true.
answer	array	undefined	Array of strings, where each string is either 'same' or 'different'. This array should be the same length as stimuli and the answers should correspond to the pairs in the stimuli array.
same_key	numeric or string	'Q'	The key that subjects should press to indicate that the two stimuli are the same.
different_key	numeric or string	'P'	The key that subjects should press to indicate that the two stimuli are different.
timing_first_stim	numeric	1000	How long to show the first stimulus for in milliseconds.
timing_gap	numeric	500	How long to show a blank screen in between the two stimuli.
timing_second_stim	numeric	1000	How long to show the second stimulus for in milliseconds. If the value of this parameter is -1 then the stimulus will be shown until the subject responds.
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).

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	string	Either the path to the image file or the string containing the HTML formatted content that the subject saw first on this trial.
stimulus_2	string	Either the path to the image file or the string containing the HTML formatted content that the subject saw second on this trial.
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 second stimulus first appears on the screen until the subject's response.
correct	boolean	true if the subject's response matched the answer for this trial.

Examples