A gradient obtained after extinction, when the extinction stimulus is represented on the continuum along which the gradient is determined. In one type, responding is first reinforced during several stimuli along the continuum and is then extinguished during only one of them. In another, reinforcement is correlated with stimulus 1 and extinction with stimulus 2, but only stimulus 2 is represented on the continuum along which the gradient is determined (e.g., stimulus 1 is a form and stimulus 2 is a color, and the gradient is determined along the wavelength continuum).