The role of a stimulus in a Behavioral Experimental Paradigm Condition is attributed to the object(s) which are presented to the subject in a controlled manner in the context of the experiment.
JT and AL
In an auditory oddball experiment, tones are the stimuli, which are categorized as either non-target (low frequency) or target (high-frequency) tones. The distinction of whether the stimulus is a target or non-target is qualified by the stimulus role.
Not all stimuli have more specific roles than just being the stimulus; in these cases, the stimulus is simply a generic stimulus. A stimulus may also have experiment-specific import to the subject, as reflected in playing the role of a reward or feedback.
We define a stimulus as a role so that ontologies of tones, lights, pictures, and other "things" can be imported as references to the objects which play the role of stimulus in a given experimental condition.
JT and AL
curation complete Dec 2010