Thank you for an outstanding issue with many intriguing articles. In “The Engine of Memory,” by Donald G. MacKay, one anecdote triggered a long-forgotten memory of my own. When Henry Molaison, MacKay's famous subject, replied “compass” when the answer was supposed to be “protractor,” he may have been answering correctly, depending on what was taught in school.

In the early 1950s, when I was in elementary school in Louisiana, we were asked to bring in some math supplies, which included a “compass.” I duly returned to school with a device for finding true north, only to produce a roomful of giggles. Everyone else had brought a protractor, which is what was expected when a “compass” was requested.

So not only do we have to be careful when selecting items to be used to test brain function, we also need to be aware of regional vocabularies!

Jill O. Goodwin
Alpine, Tex.

I am an avid reader of this valuable magazine and would like to see it keep its high quality indefinitely.

The Engine of Memory” particularly interested me. I'm a Ph.D. biochemist approaching my 50th birthday, and I am very keen on keeping my memory young. I was eager to make plans to follow MacKay's suggestions for maintaining memory. But I believe I found a logical error in the author's reasoning.

MacKay writes: “In Henry's case, this hippocampal maintenance system was defunct. Henry had no way of rejuvenating depleted memories through experience and relearning—leading to his accelerated decline.” If so, then, logically, Henry's memory decline should be across all the memories: infrequently used words as well as frequently used words and familiar but irregularly spelled words as well as regularly spelled words—not just the infrequently used and irregularly spelled words, as observed.

Therefore, although MacKay's conclusion could still be true that refurbishing old memory via a functioning hippocampus is necessary to form the memory anew, I do not believe it is a logical outcome of his observation of Henry's word-finding difficulties.

Yuan Chang
via e-mail

MACKAY REPLIES: Regarding Yuan Chang's letter, frequent use of a word prevents memory degradation, independent of the hippocampus, whose role is limited to creating new memories and re-creating memories that have become degraded because of aging and infrequent use. Because use prevents loss, it follows that neither you nor I nor an amnesic such as Henry could ever lose our memory for the meaning or spelling of a frequently used word such as “he”—which we produce and encounter many millions of times over our lifetime. Only memories for words that people use rarely and not recently—say, “sanguine”—are vulnerable to total degradation from aging.

When memory degradation does happen for rarely used words, older adults with unimpaired hippocampal mechanisms can relearn their meaning, spelling or pronunciation when they subsequently encounter them. But Henry could not relearn infrequently used information that became degraded in his later years, because his hippocampal system for creating memories to replace damaged ones was defunct. As a result, as Henry aged, more and more of his infrequently used words became unusable, at a faster than normal rate, relative to people of the same age who have intact hippocampal mechanisms and can therefore relearn and continue to use rare words, a process that reduces the overall extent and rate of memory degradation as aging progresses. Continued learning, use and encounters with rare words, spelling and other types of information therefore hold the key to maintaining your memories with aging.

Regarding Jill O. Goodwin's letter, when analyzing the hundreds of spectacular word substitutions that Henry produced in our experiments, my laboratory always ensured that they were genuine errors rather than acceptable regional variants related to Henry's Connecticut education and dialect.


Our cat Sammie, a female tortoiseshell, demonstrates on many occasions that she can think abstractly, like the animals described in “Categorically Smart,” by Andrea Anderson [Head Lines]. We have a toy basket for our two cats, which contains around five dozen cat toys, always well mixed. In that assortment there are six small balls and six pillow-shaped toys of various colors, sizes and textures. There are also about half a dozen micelike toys in two distinct variations. The remaining toys are one-offs.

About once a month, Sammie will go to the basket in the middle of the night and begin categorizing (pun intended). The next morning, we'll find all the balls, all the mice or all the pillows scattered on the floor. She never mixes types, nor does she include any of the singletons.

This behavior is spontaneous and began (and continues) without any encouragement from us. In fact, we tend to discourage middle-of-the-night cat romps. We're asleep when she goes to work and only learn of her activity the next morning. If that isn't conceptual thinking by an animal, I don't know what is!

Richard Beard
Greeley, Colo.


I was extremely disappointed with Simon Baron-Cohen's answer to the boy with Asperger's [Ask the Brains]. He did not refer in any way to the differences between autism and Asperger's, as if Asperger's is merely a different name for autism. But there are many important differences. People with autism may “have difficulty integrating complex ideas,” as he asserts, whereas people with Asperger's are actually exceptionally good at doing that. People with autism have difficulty speaking in general, but those with Asperger's speak very well—their problem is their lack of social skill and inability to use or understand pragmatics. It's too bad you couldn't find a “brain” whose field is Asperger's rather than autism.

Naomi Goldblum
via e-mail

As a person with Asperger's, I can say that many of the things Baron-Cohen wrote ring true to me. I like his use of “autism spectrum condition” (ASC) rather than “autism spectrum disorder.” Although it really doesn't make a bit of difference to me, and I would suspect that many other Aspies might feel the same, calling our state a “condition” instead of a “disorder” could in some small way help change how neurotypical people view us.

That is not to say that difficulties for those with ASC are completely the result of societal views and expectations. There are any number of different ways that ASC can affect a person adversely. For instance, some of the sensory peculiarities that many with ASC have can cause varying levels of trouble depending on how they affect an individual. I have learned to keep a pair of earplugs on me at all times for when sounds become too intense or when I'm in an area where I find certain kinds of sounds irritating.

Of course, one thing to consider with ASC is that there are a large variety of ways it can manifest. Try looking up the different symptoms (though to complement the change of ASD to ASC, they might be better called “tells”) of autism and Asperger's, and you'll wind up with a list as long as your arm. Still, if their differences can be accommodated, people with ASC can become a valuable asset rather than a burden.

I am reminded of an article I read a while back about a tech company that made it a point to hire a number of people with ASC. They would let them sit at a computer all day, churning out code. Set up the right conditions for these employees, and it's almost like having a bank of computers in the building that write code on their own.

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