Interview with Prof. Stevan Harnad

Abstract

As Alan Turing showed in his epochal work, computation is formal symbol-manipulation—reading and writing symbols based on rules that operate only on the arbitrary shapes of the symbols (whether 0’s and 1’s or the words of a natural language) not on their meanings. So where does the meaning of symbols come from? My version of this impasse was the Chinese-Chinese dictionary-go-round: How can one learn the meanings of Chinese words from a Chinese-Chinese dictionary alone? Everything is defined there, but the definitions are meaningless unless you already know what some of them, at least, mean. How to “ground” the meanings of those symbols, so the rest of them can be defined and described through words alone? That is what I dubbed the “symbol grounding problem”. The natural candidate for grounding symbols is direct sensorimotor interaction with the things the symbols refer to, so that the grounded symbol system can recognize manipulate and name them, autonomously.... These are sensorimotor and robotic capacities... To categorize is to do the right thing with the right kind of thing. The focus of my research has since been on how we acquire categories... Symbol grounding is also the necessary condition for the evolution of language, but language has to be grounded in the capacity to acquire some categories, at least, directly, through the senses, rather than indirectly, through language...