The versatile machinery of symbol-manipulation also provides a basis for structured 
representations (Marcus, 2001). Computer programs, for example, routinely use tree 
structures, constructed out of symbols that are combined via operations over variables, 
to represent a wide variety of things (such as the hierarchical structure folders or 
directories). 

Likewise, the the machinery of symbol-manipulation allows to keep track of properties 
of individuals as they change over time (e.g., in the form of database records). These 

 

 

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THE NEXT DECADE IN AI / GARY MARCUS 

capacities too seem central to human language (as in recursive sentence structure) and 
in our knowledge of individual people and objects as they change over time (Marcus, 
2001). (Chapter 5 of The Algebraic Mind gives a range of examples that lie outside the 
scope of eliminative connectionist models, many resting on the persistence of entities 
over time.)
The Next Decade in AI-