Information about the results of a process that is used to change the process itself. There are two types of feedback. Negative feedback, invented by Harold S. Black (1898-1983) in 1927 to stabilize vacuum tube amplifiers, is a circular or closed-loop causal process in which the system’s output is returned to its input, which is then compared to desired outcome in a comparator. If the desired outcome and the input deviate (i.e., if there is an error signal), then the discrepancy is corrected so that the two are equal and homeostasis is maintained. Hence, it is also referred to as deviation-reducing, error-reducing or stabilizing feedback. It is a self-regulating mechanism involved in many biological processes such EEG waves, postural control and the control of slow goal-directed movements, with Piaget even claiming that his concept of equilibration is an example of negative feedback. Positive feedback, in contrast, is when the correction is made in the same direction as the original displacement and thus serves to amplify it. Hence, it is referred to deviation-amplifying feedback. While positive feedback has been compared to a vicious circle, that has connotations of ‘misfortune’ and ‘disaster’, it is in effect the embodiment of a self-enhancing process. Thus, for example, Waddington’s concept of homeorhesis was depicted by him as a process of maintaining a balance between positive feedback (which changes the developing system) and negative feedback (which maintains its stability). Furthermore, the amplification provided by positive feedback is required for recordings of brain activity as made, for example by means of EEG and microelectrodes.
See Circular causality, Closed-loop and open-loop control, Cybernetics, Electroencephalogram (EEG), Equilibration, Feedforward, Homeorhesis, Kinesthesis, Hypothalamic-pitutiary-adrenal (HPA) axis, Motor control, Postural control, Praxis, Proprioception