In August, I was shopping at a local store. After filling my cart with various items and checking out, the bill came to $88.88.

What an interesting coincidence of numbers, I thought.

And, because I have way too much time on my hands and tend to ponder odd things a lot (just ask my wife, kid and friends), I thought about it a little more.

I bought 44 items. Four plus four is eight.

And it was August - the eighth month of the year.

And the year ended in "8."

The time I checked out was 11:32:51. If I add "11" to "32" and subtract that sum from "51," I get "8."

I bought eight bottles of soda.

I bought a bag of potatoes - there are eight letters in the word "potatoes."

This was weird stuff.

But wait - there's more.

The next day, I returned to the store to pick up a few more household items. The bill came to $33.02.

Add the numbers together and you get … eight.

Did I tap into some cosmic force built on the number 8 that affects life and living as we know it?

Had I uncovered some unknown mathematical constant that, properly interpreted, links all things, all events, all people to the power of 8?

Look out, Da Vinci Code. Take a back seat, Bible Code. We now have the Darnay Code.

Or not.

A little online research shows the "mystic" pattern of eights I've "discovered" is nothing more than one part coincidence and one part human nature.

Mathematically speaking, the chances that I would, at some point in my life out of all the times I've purchased something in a store, end up with a receipt that totals $88.88 is actually quite unremarkable. It's like flipping a coin hundreds of times and getting a streak of, say, eight heads in a row. Do something enough times and you'll get some interesting outcomes.

Calculate the irrational number Pi to enough decimal places and you start seeing interesting patterns of numbers. For example, places where the pattern "12345" shows up or your birth year.

We find things like an $88.88 receipt unusual because we remember that occurrence but tend to ignore all the times the receipt totals were not unusual (like $12.33 or $8.61 or $23.07).

This is called "availability bias." We tend to give more importance to things we remember or note than to those things that we choose not to remember or seem common.

An example of this is given in Leonard Mlodinow's book, "The Drunkard's Walk: How Randomness Rules Our Lives."

He asks which is greater: The number of six-letter words in English that have "n" as the fifth letter, or the number of six-letter words in English that end in "ing"? Most people will say the words ending in "ing" are greater - even though the two choices describe the same thing.

This is because it is easier to think of words ending with "ing" than generic six-letter words with "n" as the fifth letter.

How many times in a day do you get a receipt for some purchase? Gas, meals, grocery shopping, book store, clothing store - all those daily activities generate receipts. Multiply these daily receipts by the number of days in your life you've been able to generate receipts. You're looking at thousands, if not tens of thousands, of receipts.

It would be far more unusual to not end up with an $88.88 receipt in all those instances.

But that's not how we humans remember things.

Or look for things.

Humans, by nature, are pattern seekers. We see shapes in clouds, images in abstract art. It's believed to be an evolutionary survival thing: Seeing striped patterns helped early humans avoid dangerous animals lurking in bushes, for example.

So, by noticing that my $88.88 bill came in August, which happened to be the eighth month of the year, I found a pattern. And, in finding that pattern, I started looking for other examples of that pattern - even to the extent of trying to manipulate numbers in such a way that the results would equal eight and thereby reinforce the pattern. A pattern that is meaningless by all logical and mathematical measures, but meaningful to me only because I have created meaning in the pattern I found.

All this is one reason why some people see conspiracies in coincidental occurences or something sinister in repetitive number patterns related to the Sept. 11, 2001, terrorist attacks or supernatural secret code patterns in books and writings.

To learn more about coincidence, pattern seeking and other aspects of human nature, you might want to check out the following Web sites:

What Is Availability Bias?

www.wisegeek.com/ what-is-availability-bias.htm

A brief explanation of the topic with some related links.

Coincidence: Remarkable Or Random?

www.csicop.org/si/9809/coincidence.html

A good explanation of why coincidence is not as uncommon as you might think.

Understanding Uncertainty

http://understandinguncertainty.org

Good insights into why surprising things happen.

Theory of Physics Explains Human Patterns

www.dukenews.duke.edu/2007/06/constructal.html

Interesting research into pattern seeking in humans.

Snopes: 9-11 Coincidences

www.snopes.com/ rumors/coincidence.asp

www.snopes.com/ rumors/elevens.asp

Excellent refutations of supposed coincidences involving people, numbers and secret conspiracies related to the Sept. 11, 2001 terrorist attacks. A good real world primer on availability bias and how pattern seeking can produce just about any result you want.

20 Most Amazing Coincidences

www.oddee.com/item_ 82923.aspx

A fun page, if nothing else. From James Dean's cursed car to the bullet of destiny, read about what appear to be strange coincidences.

(Keith Darnay is the webmaster and designer for bismarcktribune.com. His Web site, featuring this column going back to 1995, is at www.darnay.com.iec.)