Pandemonium Model of Mind

Pandemonium? Chaos? Doesn’t pandemonium imply chaotic? – Yes, but ignore that The “pandemonium” term comes from the arena of demons metaphor or “the dwelling place of demons”

Selfridge’s Model Oliver Selfridge (1959) wrote “Pandemonium: A paradigm for learning” for the Symposium on Mechanisation of Thought Processes This took the then novel approach of suggesting that pattern recognition could be modeled as – Parallel – Connectionist – Adaptive learning

Selfridge’s Model (cont.) The Story – Once upon a time there was Pandemonium. – In Pandemonium there dwelt many very ugly and intelligence challenged (a.k.a. stupid) demons. – There was only one little hole to look out of and only one demon could look out of it. – This image demon could only paint what he saw and show it to the demons in the row standing behind him. – The demons in the next row, being of stout body and little brain, could each only recognize one type of feature. – Since there was little else to do in these cramped quarters, the feature demons got excited and jumped up and down if they recognized their feature. – The demons in the row behind them were unable to see the painted image because they were too dumb or scared to turn around and were facing the wrong way. – Each of the cognitive demons, however, were connected to specific feature demons by ropes. Based on the elasticity of the ropes, which varied, the cognitive demons would get painful tugs from their connected feature demons. – The resulting shrieks from the row of cognitive demons were louder from the demons who had more of their connected feature demons excited. – Finally, there was the grand high decision demon who really just wanted quiet. Upon hearing the calamity from the cognitive demons, the decision demon would yell out the name of the cognitive demon shrieking the loudest (with a threat to make him turn around and look at his brother demons – a fate worse than death)

Selfridge’s Model (cont.)

Selfridge showed that his pandemonium model could distinguish dots from dashes in manually keyed Morse code (1959) and 10 different hand printed characters (1960) There were two learning mechanisms – Update of link weights (rope elasticity) between feature and cognitive demons based on a hill climbing technique – Using one of the first examples of genetic algorithms to cull low valued demons and replace them with new mutated or mated demons based on the highly valued demons

Jackson’s Model In 1987, John Jackson extended Selfridge’s model His model includes demons that can cause actions in the external (outside their Pandemonium box) world and can act on other demons Rather than the static four levels, think of a chaotic arena with no obvious layering

Jackson’s Model (cont.) Demons are still connected to specific other demons through weighted links One or more demons still serve the purpose of being sensory image demons However, a dynamically changing set of demons is “on the field” performing their task and, consequently, exciting associated demons in the stands The demon in the stands that yells the loudest gets to come down to the playing field displacing one of the demons already on the field

Jackson’s Model (cont.) The learning mechanism is slightly different than Selfridge’s – Some links are built in – Others are created How?

Jackson’s Model (cont.) The creation of links between demons is an ordered Hebbian scheme – Based on the gain, all demons on the playing field together have their link strengths adjusted – Demons on the field get stronger adjustments to newly arriving demon than vice versa Demon on the playing field Newly arriving Demon

Jackson’s Model (cont.) The gain has an important part to play – Gain is the system’s assessment of how well it is doing. If everything is going well, the gain will be positive and high, otherwise is could be negative – This means that demons tend to reappear on the playing field together if they are associated with improved conditions Demon on the playing field Newly arriving Demon

Jackson’s Model (cont.) Calculating the gain is the manner in which this system determines if it is meeting its goals or not This is done by the sub-arena The sub-arena also takes care of – Low-level sensory input – Performing actions instigated by demons on the playing field

Jackson’s Model (cont.) Jackson also has the notion of abstract concepts or “concept” demons – Conglomerations of demons that have become highly associated into a single demon (think chunking) – The original singleton demons remain around to do their thing – Original specifications of concept demons were vague – mainly because Jackson didn’t know how to do them

Pandemonium in IDA IDA uses Jackson’s version of the Pandemonium model to learn associations between codelets The metaphor of an arena is combined with the theater metaphor so that the spotlight of “consciousness” shines on coalitions of codelets on the playing field

Associations Association strengths are updated in the manner of Jackson’s Pandemonium model except that codelets not in the spotlight get very weak association updates Codelets in the spotlight get full association updates Associations also decay over time so that associations that are not reinforced die away

Associations (cont.) Some associations are built in a priori Others are learned The strength of the associations is used to determine how coalitions are created

Gain Gain is calculated using codelets that are designed to recognize particular environmental or internal states These codelets are considered emotion codelets – States recognized by these codelets elicit an emotional response manifested as changes to the drives of the system and the gain

Summary The result is that codelets become strongly associated if they elicit positive emotional responses Coalitions, which form the contents of consciousness, change over the course of a run