Stimulus

Describes each of the stimuli that were shown during an trial.

note

Each row of Stimulus table corresponds to a stimulus in a trial. Each trial can contain different number of stimuli.

Key

Field	Type	Requirement	Description
stimulus_id	PRIMARY KEY	required	Primary key of the Stimulus table. Reference to this identifier in other tables are thus named stimulus_id.

Context

Field	Type	Requirement	Description
trial_id	id	optional	Refers to the trial_index in the Response table and indicates in which trial this stimulus was shown.
response_id	id	required	Refers to the response_id in the Response table and indicates for which response this stimulus was shown.
object_id	string	optional	A stimulus is defined by a set of features. This variable is used to identify each time the same stimulus features were used.
presentation_id	string	optional	In a multitasking setting, a particular instance of a stimulus (e.g., the current letter "A") may be used by multiple tasks at the same time (e.g, in the dual N-back task). Because these are different trials, they will have different trial_id values and hence will have different rows in the Stimulus table. We use presentation_id to indicate that a given stimulus is in fact the same instance across those trials.
index_in_trial	integer	optional	Refers to individual stimuli within the sequence or set of stimuli shown during a trial.

When

Field	Type	Requirement	Description
onset	float	required	Duration between the start of the trial and the appearance of the stimulus, in seconds.
duration	float	required	Describes for how long this stimulus was displayed after its onset, in seconds.

Where

Field	Type	Requirement	Description
panel_id	string	optional	Identifier of the panel this stimulus is displayed over.
x_screen	integer	optional	X coordinates of the stimulus on the screen in pixels.
y_screen	integer	optional	Y coordinates of the stimulus on the screen in pixels.
x_viewport	float	optional	X coordinates of the stimulus on the screen expressed as a fraction of the screen width.
y_viewport	float	optional	Y coordinates of the stimulus on the screen expressed as a fraction of the screen height.

What

Field	Type	Requirement	Description
description	string	required	A human readable, compact description of the main aspects of the stimulus. The description for a given stimulus depends on the task but follows a specific template for a given task. Because of this, it looks like the description could be parsed and converted into a more structured format---however, this is not the intention; structured data will be available in other tables; here, description is for human readability and facilitates the understanding of the data.
source	string	required	Refers to the specific generator or set the stimulus belongs to.
source_type	enum	optional	A stimulus is typically created using a particular procedure/algorithm ("generator") or is sampled from a particular set ("set"). This variable indicates which of these two applies for the current stimulus.
index_in_source	integer	optional	When a stimulus is picked from a particular set (e.g., "digits1to9"), this index refers to the index within that set.
role	enum	required	Describe the role that the stimulus plays in the trial, e.g., "target".

How

Field	Type	Requirement	Description
animation	string	optional	Describes the animation used to display a specific stimulus in a human-readable format. For example, "fadeIn 3s" indicates a 3-second fade-in animation.