Contingent Negative Variation - Main Paradigms

Main Paradigms

Walter and colleagues conducted the experiment in the chronometric paradigm. They had noticed that the electric response became attenuated, or habituated when a single stimulus is repeated. They also noticed that the amplitude of the electric response returned when a second stimulus was associated with the first stimulus. These effects were strengthened when a behavioral response was required for the second stimulus. In a chronometric paradigm, the first stimulus is called the warning stimulus and the second stimulus, often one that directs the subject to make a behavioral response, is called the imperative stimulus. The foreperiod is the time between the warning and imperative stimuli. The time between the imperative stimulus and the behavioral response is called the reaction time. The CNV, then, is seen in the foreperiod, between the warning and imperative stimulus.

Walter and colleagues also noticed that electric responses to warning stimuli seemed to have three phases: a brief positive component, a brief negative component, and a sustained negative component. They noticed that the brief components varied due to sensory modality, while the sustained component varied with the contingency between the warning and imperative stimuli and the attention of the subject. They labeled this component the “contingent negative variation” because the variation of the negative wave was contingent on the statistical relationship between the warning and imperative stimuli.

In their study, Walter et al. (1964) presented clicks or flashes, singly or in pairs, at intervals between 3-10 sec. The warning stimuli were single clicks or flashes and the imperative stimuli were repetitive clicks or flashes. The modality of the imperative stimuli was opposite that of the warning stimuli. The behavioral response was a button press which terminated the repetitive stimuli.