Book Review : Well-Chosen Words on Linguistics : Words in the Mind: An Introduction to the Mental Lexicon by Jean Aitchison (Basil Blackwell: $15.95, paper; 229 pages)

Use of language is perhaps the most distinctively human skill. We do it effortlessly and without thinking much about how it is done.

But this is no small feat. The average adult has a vocabulary of between 50,000 and 250,000 words and can put them together in novel ways at a trice. We are able to speak and understand as many as five words a second.

Every day each of us hears sentences we have never heard before. We convey practical information, emotions, insights and ideas and everything in between. How is this done? How are all those words stored in the brain so efficiently that they can be retrieved for speaking or for understanding so quickly? How is the mental dictionary arranged?

In recent years, many linguists have tackled these questions and others related to them, and while the answers are far from in, enough information has been gathered to make some good guesses.

Clear, Thoughtful, Speculative

In “Words in the Mind,” Jean Aitchison, a linguist at the London School of Economics, makes this body of scholarship available to interested lay readers. It is a fascinating book, clear, thoughtful, speculative, yet grounded in facts and experimental observations.

Aitchison tells us what is known and what is not known about how we speak. She weighs the evidence, discarding some ideas and embracing others, presenting the arguments pro and con all the while. From the start, I was captivated.

There are two parts to speaking, Aitchison tells us, words and syntax, which she likens to bricks and mortar in putting up a building. (Her analogies throughout the book are first-rate.) Words are the bricks with which we build sentences, and syntax is the mortar that holds them together in a comprehensible way.

Linguists have traditionally viewed syntax as the hard part of language, and they have considered words--vocabulary--as a secondary matter. Aitchison turns that view upside down. Learning a few dozen rules of syntax, she says, is as nothing compared to the ability of adults to store in memory, discriminate, characterize and retrieve tens of thousands--even hundreds of thousands--of individual words with amazing speed.

“Words are not just stacked higgledy-piggledy in our minds, like leaves on an autumn bonfire,” she writes. “Instead, they are organized in an intricate, interlocking system whose underlying principles can be discovered. . . . The large number of words known by humans, and the speed with which they can be located, point to the existence of a highly organized mental lexicon.”

But, obviously, language researchers cannot look directly into the brain to discover what this organization is.

The data for linguists consists of experiments, many of them cunning, on how people remember words, how they forget them, how they learn them, how they manipulate them and how and why they mistake one word for another.

One thing is certain: the mental lexicon is not like the unabridged dictionary on your shelf. Words in the mind are not stored alphabetically, though, Aitchison notes, “People tend to recall the beginnings and ends of words they cannot otherwise remember.”

Further, she says, “Certain features of a word are more prominent in storage than others, and people home in on these when they are selecting a word. Above all, people seem to know about the beginning, to a lesser extent the end, and the general rhythmic pattern.”

Aitchison shows that a dictionary model for the mental lexicon is much too rigid, starting from the fact that most words themselves are not clearly and absolutely defined in our minds.

There are a few words, such as bachelor , whose meanings are essentially fixed. A bachelor is an unmarried adult male. But the meanings of most words are much more amorphous. Aitchison describes an experiment in which subjects were asked to label various items of pottery as a vase, a cup or a bowl.

Basically, this has to do with shape and whether or not the item has a handle. But, she reports, “A bowl remained a bowl if it was full of mashed potatoes but tended to be relabeled as a vase if it contained flowers, and a cup if there was coffee in it.”

Furthermore, our use of words admits of great flexibility. “ Headache pills demolish headaches, fertility pills produce fertility and heart pills aid the heart.”

These findings are reinforced at every level of research into the organization of our linguistic abilities. “The mental lexicon is not a fixed dictionary with a set amount of information about each word, but an active system in which new links are perpetually being formed,” Aitchison says.

Aitchison leads us by the hand through many of these efforts, pointing out their strengths and weaknesses with admirable clarity and no small humor. Each chapter ends with a very good summary that ties together and reinforces the preceding pages.

Her conclusion is that the mental lexicon is dynamic, akin to “complex electric circuitry, in which current flows backwards and forwards between particular points.”

But she concedes that much work is yet to be done.