Piero Scaruffi(Copyright © 2013 Piero Scaruffi | Legal restrictions )
These are excerpts and elaborations from my book "The Nature of Consciousness"
In the 1920s the German psychologist Otto Selz had a fundamental intuition: to solve a problem entails recognizing that the situation represented by the problem is described by a known “schema” and fill the gaps in the schema. A schema is a network of concepts that organize past experience.
Given a problem, the cognitive system searches the (long-term) memory for a schema that can represent it. Given the right schema, information in excess contains the solution.
Representation of past experience is a complete schema. Representation of present experience is a partially complete schema. By comparing the two representations (the complete schema that was created in the past with the partial schema that describes the current situation) one can infer (or, better, “anticipate”) something relative to the present situation. For example, a schema tells us how to cross a street. Whenever we want to cross a street, we look for (i.e., we know that there must be) a traffic light. Thanks to the schema's anticipatory nature, to solve a problem is equivalent to comprehending it, and comprehending ultimately means reducing the current situation to a past situation.
In the 1960s Marvin Minsky rediscovered Selz’s ideas: his “frame” is but a variation on Selz’s schema.
A “frame” is a packet of information that helps recognize and understand a scene. It represents stereotypical situations and finds shortcuts to ordinary problems. A frame is the description of a category by means of a prototypical member plus a list of actions that can be performed on any member of the category. A prototype is described simply by a set of default properties. Default values, in practice, express a lack of information, which can be remedied by new information. Any other member of the category can be described by a similar frame that customizes some properties of the prototype.
Technically, a frame can provide multiple representations of an object: taxonomic (a conjunction of classification rules), descriptive (a conjunction of propositions of the default values) and functional (a proposition on the admissible predicates).
Memory is a network of frames, one for each known concept. Each perception selects a frame (i.e., classifies the current situation in a schema) which must then be adapted to that perception; and this is equivalent to interpreting the situation and deciding which action must be performed. Reasoning is adapting a frame to a situation. Knowledge imposes coherence on experience.
Because it does not separate cognitive phenomena such as perception, recognition, reasoning, understanding and memory which seem to occur always at the same time, the frame is more biologically plausible than other forms of knowledge representation that treat them as independent and sequential processes. Moreover, it offers computational advantages, because it focuses reasoning on the information that is relevant to the situation at hand.
Minsky later generalized the idea of the frame in a more ambitious model of how memory works. When a perception, or a problem-solving task, takes place, a data structure called "K-Line" (Knowledge Line) records the current activity (all the “agents” active at that time in memory). The recall of that event or problem is a process of rebuilding what was active (the agents that were active) in memory at that time. Agents are not all attached the same way to K-lines. Strong connections are made at a certain level of detail, the "level-band", whereas weaker connections are made at higher and lower levels. Weakly activated features correspond to assumptions by default, which stay active only as long as there are no conflicts. K-lines connect to K-lines and eventually form societies of their own.
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