After a discussion of the possible connections between quantum mechanics and consciousness, and an examination of the circumstances under which some properties of a macroscopic system may be described by a quantum mechanical wave function, we propose three types of experiments in which one may search for the possible existence of quantal interference in mental events.

Classical and quantal physics are fundamentally different in the way that each deals with complexity. We examine both the algorithmic and the computational aspects of this difference. Any comprehensive deterministic theory must contain a certain ineffectiveness in producing long-term predictions of the future, whereas a probabilistic theory is not so handicapped. The relevance of these considerations to chaos is discussed.