Illustration: Larry Jost

Clued In to the Brain

When Dr. Fill, a crossword-solving program, took on the six hundred contestants in this year’s American Crossword Puzzle Tournament, its creator predicted it would finish among the top fifty. Seven expert-level puzzles later, it placed one hundred forty-first. Dr. Fill’s less than stellar performance highlights the complexity of the processes that go on in a human brain as it is solving a crossword. For someone like Raymond Nickerson, G65, who is both an avid crossword puzzle solver and a research professor of psychology at Tufts, those processes provide a glimpse into how the mind works.

Nickerson examined the subject in an essay published last year in the journal Psychonomic Bulletin and Review. “It occurred to me,” he says, “that crosswords intersect with a great number of things that I’m interested in, particularly reasoning and memory.” For example, he says, “in problem solving, we tend to assume that we have found the solution, and once we do, that it’s the only solution to be found. Typically, we don’t think further about the problem and discover that there may be other solutions.”

The same happens in puzzle solving. If we’re looking for a noun, we don’t think to look for a verb. And if we find a noun that fits, we don’t explore other possibilities. “That’s somewhat characteristic of the way we solve problems in general,” Nickerson says.

As much as science has uncovered about the mind, mysteries abound. Little is known, for example, about how we search our memories. In a crossword puzzle, there are a variety of clues for each word: definitions (some more subtle or tricky than others), the length of the word, and perhaps some letters filled in by intersecting clues. Seasoned solvers also look for hints contained within the clues—question marks or abbreviations—and they know that a clue and its answer are usually expressed in the same part of speech.

And yet, Nickerson says, we have no idea how each brain goes about the process of combing its database of knowledge to find an answer. Quick, think of a four-letter word ending in bt. Most people can produce the word debt almost instantly. “How did you do that search?” Nickerson asks. We can look for words by meaning, by partial length, by observing letters in certain positions, by visual cues, by auditory cues, or by some combination of those. But, he says, “it seems unlikely that a search of my entire lexicon, or anything close to that, is required.”

For that matter, do we even search for words at all? It might be easier to search our memory on the basis of letters, syllables, phonemes (units of sound that distinguish one word from another) or morphemes (meaningful linguistic units of a word).

Sometimes the answer is stuck on the tip of your tongue. Often, Nickerson writes in his journal essay, “I am not immediately able to call the target to mind, but I have a strong sense that I will be able to do so with the help of additional clues or, perhaps, just with the passage of time. Author of ‘The Ugly Ducking’ would evoke that feeling for me.”

Will Shortz, the puzzle editor of the New York Times, agrees that sometimes the best strategy for when you’re stumped is to leave the puzzle and come back later. “Perhaps the brain works subconsciously on problems in the interim,” he writes in a piece titled “How to Solve the New York Times Crossword Puzzle.” “A fresh look at a tough puzzle almost always brings new answers.”

This phenomenon is, of course, not limited to crossword puzzles. In psychological terms, Nickerson says, the creative problem solving that continues below the level of awareness—an example would be the dream that supposedly gave Dmitri Mendeleyev the insight for his periodic table of elements—is known as incubation.

Both the scientific literature and popular media have looked at the idea that mental gymnastics such as doing crossword puzzles keep the brain agile and can help ward off dementia and Alzheimer’s disease. Last year, for example, an observational study conducted by medical researchers of 101 elderly New Yorkers found that “late life crossword puzzle participation, independent of education, was associated with delayed onset of memory decline in persons who developed dementia.”

“I tend to believe it, because I want to believe that doing crosswords is a way to postpone the ravages of time,” Nickerson says. “In the meantime, whether it works or not, it’s still pleasurable.”

HELENE RAGOVIN is a senior writer in Tufts’ Office of Publications, editor of Tufts Dental Medicine, and a crossword fan who always has a puzzle in progress.