Human cognition

Overview
Human cognition is the study of how the human brain thinks. As a subject of study, human cognition tends to be more than only theoretical in that its theories lead to working models that demonstrate behavior similar to human thought. The extent to which these models can be measured as similar to, or indistinguishable from, human thought is the measure of the accuracy of the human cognition model. The terms cognitive modeling, and Cognitive architecture are sometimes used as synonyms of human cognition. Artificial Intelligence (AI) is often defined with reference to human cognition. The study of natural language understanding is the subfield of human cognition that seeks to model the way the human brain processes and understands spoken human languages, such as English language speech.

Background and history
One could argue that human cognition began with the mathematical musings of the ancient world that attempted to mathematically codify logic. Modus ponens is a simple statement from that era that says, "If one knows that A implies B (written as: A → B) is a true statement, then one knows that if A is true, then B is true." Successive application of the modus ponens principle can yield logical "reasonable" conclusions that may not be as apparent to the casual observer. For example, given the set of the following four statements: C → D, B → C, D → E, and A → B, and also given that you know that A is true, one can conclude that E is true. Is that as easily apparent as seeing that B is true? Modus ponens is the basis of the human cognition model that elicits the human-like deductive reasoning in modern rule-based expert systems.

The English mathematician Alan Turing gave us the Turing Theorem, which is the theoretical basis for John von Neumann's Von Neumann machine which, in turn, became the theoretical basis of the modern digital computer. The Turing Theorem is the statement and proof that shows that all problems that can be solved, can be solved by first building a theoretical state-space of all possible state transitions and then traversing this state space until the problem solution is found. Turing was personally interested in creating a machine that could reason like a human, and his theorem was a significant contribution toward that end. We now know that human brains are not very similar at all to modern digital computers, but Turing's and Von Neumann's work gave us the tools to get started in building computer models of human cognition.