Three directions in research on auditory scene analysis

Research on auditory scene analysis (ASA) began with some simple laboratory phenomena such as streaming and illusory continuity. Subsequently, research has gone in three directions, downwards towards underlying mechanisms (by neurophysiologists), upwards towards system organization (by computer scientists), and sideways towards other species (by neurobiologists). Each direction has its challenges. The downward approach sometimes takes a phenomenon-oriented view of ASA, leading to simple explanations of a single ASA demonstration, such as streaming, with no obvious connection to any larger system. Research done by the upward approach usually takes the form of a computer program to achieve ASA in a working system, often neglecting known facts about human ASA, in favor of mathematically understood principles. The sideways approach often finds that non-human animals can respond to an important sound despite the presence of other interfering sounds. However, there is no reason to believe that a frog, a fish and a human accomplish this by means of the same mechanisms. So finding out how some animal does this, while interesting in its own right, may shed little light on how humans do it. I will describe some properties of the human ASA system that should be borne in mind when manufacturing explanations.