1. A method of assessing neural excitation by a given stimulus based on interaction of the given stimulus and another stimulus, each stimulus applied to at least one electrode in an array located adjacent a region containing neurons subject to the assessment, said method comprising: iteratively presenting a first stimulus at increasing intensity levels until the first stimulus is perceptible thereby establishing an unmasked threshold; and iteratively presenting a sequence of a masker stimulus followed by the first stimulus at the unmasked threshold level, each iteration increasing a level of the masker stimulus until the first stimulus is no longer perceptible thereby establishing a masked threshold.