Some comments on informational masking

While informational masking (IM) has been investigated for almost a half century, only recently have there been efforts to develop a principled definition of this class of interference effects among sensory stimuli. This paper briefly review the history of IM and discusses some recent efforts toward a definition. Some experiments with tonal patterns are then described that demonstrate close associations between the effects of IM on detection and on discrimination.It is proposed that the varieties of IM revealed in recent research may not all be reasonably attributed to a single explanatory mechanism, even a fairly complex one. At the least IM effects associated with signal-masker similarity (S) are readily distinguised from those resulting from trial-to-trial stimulus uncertainty (U). A corresponding distinction may usefully be made in definitions and models, dealing separately with "s" and "u" type of IM.