Research Issues

I dream, if a computer could understand language, as humans do. No more than a dream, at least up to now. At present, computers cannot see meanings. Since language understanding is to obtain meanings from a sentence, nothing can be understood without meanings. In these days, elaborate computer programs can correctly deal with grammars, and can even play language games with us by juggling words. But still they never understand languages. It is impossible; until, at least, they can handle meanings.

What, however, is a meaning, in the first place? Although many studies are trying to describe meanings (or `semantics') by symbolic systems, they do not tell us what is understanding. Even if we made a program to convert from a symbolic system (language) to another symbolic system (semantic representation), we couldn't say the program understands something. Some other studies try to emulate semantic behavior in language by using statistics and thesaurus, achieving a higher precision of natural language processing. However, it is far from understanding language.

One approach to know meanings is to investigate how a meaning is handled by human beings. We know it happens nowhere but in the brain, the seat of the thought, memory and consciousness. The brain, which can understand a sentence, is able to associate the sentence with the brain's surrounding world, sensory input and experience. This association should be a meaning, what the current computers don't have. The way of making associations is unique to the architecture of the brain; it is worth pursuing in order to achieve the dream.

Due to the high complexity of the brain, the physiological analysis of the brain does not reach the representation and handling of meanings. The long history of brain science has succeeded to elucidate shallow parts of the brain function, such as sensory analysis and motor control mechanisms. Recent studies enlightened more deeper parts of the animal brain, such as place-coding in the rat hippocampus. However, since the meanings and languages are in the deepest part in the human brain, our knowledge is too little to see the mechanism.

I'm trying to solve this from a viewpoint of our starting point, language. Language is an expression of a meaning in the brain, which has evolved along with the human beings over thousands of years. Structures, constructions, and contents of sentences are all the reflection of the brain mechanism of meanings. It is said that the language also reflects cognitive frameworks. Language gives us both requirements and clues to the meanings in the brain; they can be the key to solve the mechanism of meanings.