When Dec 25th Isn’t Christmas Day

In celebration of the holiday season, Sci went looking for something seasonal. But referring constantly to things like how many calories we eat around this time (Sci is no exception) is really a downer. So this season, Sci decided to find out what would happen if you plug the word “christmas” into pubmed.
It turns out there are a lot of people named Christmas.
But Sci ALSO came across this study, which she found to be a really really cool phenomenon of SCIENCE! And so, as her holiday gift to you today, she presents you with this:
ResearchBlogging.org Cappelletti et al. “A case of selective impairment of encyclopaedic numerical knowledge or ‘when December 25th is no longer Christmas day, but ’20 + 5’ is still 25′” Cortex, 2006.
One of the things Sci finds interesting about this paper is the idea that the brain distinguishes between two “types” of numbers. Numbers that…are numbers, and numbers that MEAN something.


When is a number more than just a number? When it’s an encyclopedic number. This is when numbers acquire additional meanings beyond just a quantity. This is a little bit of a fuzzy definition, but suffice it to say that “3 coins” is a number, but the “third page” is an encyclopedic number. These numbers also tend to have nominal use as identifiers, for example of things like movies (“2012”) or dates like your birthday, or Christmas. These are nominal number assignments, where a number is associated with an additional meaning, and so they also involve additional information. This also works for any number that you can’t use COUNTING for, but for which you have to access additional information, like how many molecules are in a mole. These are cardinal encyclopedic numbers, which are quantifiable numbers, but associated with different aspects of remembering them rather than doing the math.
But there’s not a lot of knowledge on how these numbers are processed, and whether primary numbers (being able to count that a horse has four legs or figuring out 7+5) are processed differently from encyclopedic numbers. We know that the parietal lobe of the brain is involved in processing things like quantity. And it seems that while normal numbers require just numerical memory, encyclopedic numbers require both numerical memory and a good amount of language memory as well. It used to be thought that if you had language memory, and numerical memory, you should have no problem with encyclopedic numbers.
But could there be more to it?
The patient suffered a “traumatic assault” (not sure what happened and they didn’t elaborate), and the resulting damage resulted in classic temporal love epilepsy, which gave him seizures. Interestingly, after that, the patient complained that he had no memory for things like dates anymore. He couldn’t remember telephone numbers or PIN numbers, and I’m sure he got crap from his significant other when he entirely forgot their birthday. So they took him in and started a battery of tests.
The guy appeared to be fine, though not the smartest bulb by any means. His memory functions were NORMAL. He appeared to pass all the tests involving semantic knowledge, he had no problem recalling the meaning of words. Where he began to trip up was when they asked him to relate his autobiography. He lost a lot of points on tests by being unable to fill in the numerical information.
But when he was given a basic math test, the patient was fine. He could do complicated multiplication problems (though nothing beyond that due to a low level of education). So what was going on?
The problems really emerged in his tests for encyclopedic memory. He could answer normal, relatively difficult questions, but was unable to remember names and answers that involved NUMBERS, particularly encyclopedic numbers. For example, when asked what day was Christmas Day, he’d be unable to say “Dec. 25th”‘ but he was just fine when answering “what is 20 + 5”. This was entirely due to memory loss, not an inability to understand the questions. In many cases, like “how many people are on a football team”, he could DESCRIBE the answer just fine, but was unable to name the numbers involved. He could describe the plot of “Oceans 11”, but couldn’t remember the title.
But the final question was whether this problem was a difficulty in RETRIEVING the information that Dec 25th = Christmas, or an actual loss of the information itself. To find this out, they had him perform a task that included “priming” information, vs information that is non-priming. For example, “Santa” would be a prime to your encyclopedic memory to say “Dec. 25th” when asked what date Christmas was. The patient showed a major difference here, where the “priming’ gave him no advantage in remembering the number compared to non-priming information. In contrast, controls who took the test remembered dates father when they were “primed” with information that aided them in retrieving the encyclopedic number. They also administered tests asking him to recognize encylopedic numbers. The results of all the tasks made it pretty obvious that what the patient suffered was a LOSS of the encyclopedic imformation, as opposed to an inability to retrieve it.
Further studies also showed that the patient was unable to remember NEW encyclopedic dates. He could remember normal numbers, but not numbers associated with things like dates that meant something.
The interesting thing about this is that previous studies show that numerical knowledge AND language processing knowledge are necessary for encyclopedic numbers. He still had both language processing and numerical knowledge, and did fine with just the numbers themselves. But just because they are both necessary, doesn’t mean they are SUFFICIENT. In this case, they were not sufficient at all, implying that there is something else at work, which this patient is missing, that is also necessary to allow for encyclopedic knowledge. What it is, we don’t know yet. But the patient DID do better with encyclopedic memory when he had PICTURES (like, say, Santa or Christmas trees), to jog his associations. To Sci, this means the information probably wasn’t lost (though she’s disagreeing with the authors here), but that the normal routes of processing were impaired, andCAPPELLETTI, M., JANSARI, A., KOPELMAN, M., & BUTTERWORTH, B. (2008). A case of selective impairment of encyclopaedic numerical knowledge or ‘when December 25th is no longer Christmas day, but ’20+5′ is still 25’ Cortex, 44 (3), 325-336 DOI: 10.1016/j.cortex.2006.07.005 that another route might exist via visual stimuli.

7 Responses

  1. I agree with you that these results are far from showing that information is gone and instead suggest that a particular set of connections is lost. It reminds me quite a bit of optic aphasia and the connectionist modelling work that David Plaut has done. Also, the increased efficacy of pictorial primes doesn’t even need to point toward a crucial modality difference because pictures are almost always richer stimuli – worth 1,000 words as they say.

  2. once you get started with providing cues for memories, you’re moving into new territory. free recall vs cued recall is an interesting topic in itself.
    i do find it interesting that such memories were only affected when numbers were involved. i’m wondering how much numeric association is required as a threshold- as in, phone numbers vs the score of yesterday’s hoops game vs your 5th birthday in the year 19xx vs your best friend’s first name.
    definitely lots of info missing here, but an intriguing case!

  3. once you get started with providing cues for memories, you’re moving into new territory. free recall vs cued recall is an interesting topic in itself.
    i do find it interesting that such memories were only affected when numbers were involved. i’m wondering how much numeric association is required as a threshold- as in, phone numbers vs the score of yesterday’s hoops game vs your 5th birthday in the year 19xx vs your best friend’s first name.
    definitely lots of info missing here, but an intriguing case!

  4. Classic temporal love epilepsy? Sounds awesome! Just replace epilepsy with ecstasy and you’ve named yourself a new cocktail!
    I friend of mine had a seizure, and for a day or so afterwards couldn’t say certain numbers (especially distances like twenty metres), but he could hold up the right number of fingers. It was unbelievably frustrating for him.

  5. I’m just the opposite. I remember phone numbers and birthdays of childhood friends that I haven’t seen in over 30 years.
    Over all, I don’t have a phenomenal memory or phenomenal mathematical skills.

  6. I stumbled across this page looking for information as to why I have very little ability to remember numerical data.
    I can’t do birthdays (except mine) at all, use a riddle to remember my wife’s, I learned my ATM pin by using a touch-tone phone for the sound, then remembering sound and the motion, I also can’t remember that Christmas is the 25th, though I know with certainty is must be one of 24, 25 or 26. Overall it’s quite inconvenient.
    If there are more links, or information you can post regarding this topic it would be much appreciated.

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