A cognitive computer combines artificial intelligence and machine-learning algorithms, in an approach which attempts to reproduce the behaviour of the human brain.
An example is provided by the IBM company's Watson machine. A subsequent development by IBM is the TrueNorth microchip architecture, which is designed to be closer in structure to the human brain that the von Neumann architecture used in conventional computers.
The IBM cognitive computers implement learning using Hebbian theory. Instead of being programmable in a traditional sense within machine language or a higher level programming language such a device learns by inputting instances through an input device that are aggregated within a computational convolution or neural network architecture consisting of weights within a parallel memory system. An early instantiation of such a device has been developed in 2012 under the Darpa SyNAPSE program at IBM directed by Dharmendra Modha.
Criticism
There are many approaches and definitions for a cognitive computer, and other approaches may be more fruitful.