A measure of responding in the presence of different stimuli as a function of their location along a continuum . Gradients are ordinarily determined b presenting the stimuli successively but in irregular order during extinction. The slope or steepness of a gradient is determined by how much change in responding occurs from one point on the continuum to another; the, larger the change, the steeper the gradient. The case in which responding does not change is usually be called a flat gradient, although it may also called the absence of a gradient. See also extinction gradient, generalisation gradient, inhibitory gradient, post-discrimination gradient.