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Assumptions have a Sell By date


We can't expect to innovate new products, services, techniques, etc. without challenging our assumptions. Have some of your assumptions "gone off"? How frequently are you checking? In other words, do you have a plan in place for regularly sniffing the milk? I swear that half my battles at Sun were about questioning assumptions... many of which had been around long enough to be science fair projects.

When you're stuck with the inertia of outdated assumptions, you're stuck with incremental (not revolutionary) improvements. The Head First books, for example, would never have happened if we hadn't been able to convince Tim O'Reilly that typical programming books were based on an assumption that was just plain wrong.

We all talk about challenging assumptions, but what does that really mean? Because if we don't go deep enough--deep enough to get to the foundation on which all subsequent assumptions are based--we might as well not waste our time. Here's a typical scenario:

Fred: Let's challenge our assumptions here people... are we certain that customers won't like this?

Jim: Yes.

Fred: How do we know? Where's the data?

Jim: It came out clearly in focus group testing.

Fred: But how recent were those focus groups?

Jim: Very recent--less than a year ago.

Fred: But what did they actually test?

Jim: They tested this exact feature.

Fred: OK, then let's move on. Tell engineering to cut that from the spec.

There's a textbook example of challenging an assumption, without challenging the assumptions below. The underlying, unchallenged assumption here is that focus groups work (when we know focus groups are notoriously unreliable for many things).

It's assumptions all the way down.

A few tips:

1) List them.
Yes, that's a "duh" statement, but seriously... how many times do you actually SEE assumptions explicitly called out?

2) Give them a Sell By date.
Slap a date on these puppies and have a system in place for knowing when to sniff them! Whether its a database or spreadsheet or just a big chart on the wall that y'all agree to review once a month or quarter or whatever, the point is to guarantee that you really WILL sniff them all on a regular basis.

3) Challenge them all the way down.
Question something and then question what it's based on, and then what that is based on, and so on... until you get to the bottom. And when you hit bottom, keep questioning until you're absolutely positively sure it's the bottom.

4) When you challenge an assumption, make it fight for its life.
Put it on trial. Force it to defend itself. Be relentless. Be skeptical. Be brutal.

These are all rather obvious tips, yet so often overlooked. But simply listing and challenging our assumptions on a regular basis isn't the biggest problem.

The really big problem is the assumptions which are so ingrained that we don't even know they're assumptions. They become an accepted Law of Physics, as good as gravity.

It does little good to list (and date) our assumptions, if the most crucial ones--the ones that could lead to the biggest innovations and breakthroughs--never make it to the list. It's not enough to say, "So, what are our assumptions here?" We have to ask--and keep asking--"So, what are we accepting as fact and not questioning as an assumption?" In other words, "What are our hidden assumptions? What do we believe implicitly?"

It's not enough to "sniff the milk." We have to recognize that some of the things which we believe are part of the fabric of our universe might just be milk in disguise.

And while I'm using Fundamental Laws of Physics as a metaphor for the things we believe implicitly about customers, products, etc. it seems that even the real laws of physics need a sniff from time to time.

UPDATE: but the universe appears to persist. Or does it? Assumptions all the way down... ; )

Posted by Kathy on August 21, 2006 | Permalink


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That's an amusing Discover article to link to on the same day that this press release came out. :)

Posted by: Jocelyn | Aug 21, 2006 4:00:59 PM

And never assume you learn anything from a focus group!

Posted by: John Dodds | Aug 21, 2006 4:05:02 PM

Jocelyn: that's too good. too too good! I'm updating the post. I'm also reminded of my father's Life magazine with an ad that says, "Four out of Five doctors recommend [insert brand] cigarettes." And don't get me started with what we're supposed to be eating. Carbs, protein, and fat all take turns being bad, then good, then bad, then good, then...

John: You obviously only skimmed the post and did not read that part carefully. Bad, bad John. No cupcakes for you ; )

Posted by: kathy Sierra | Aug 21, 2006 4:38:00 PM

Challenging assumptions? That can be hard.
Convincing other people to challenge their assumptions? Whoa!

I'm convinced that there is a certain brain wiring that means that some people are comfortable with, and have an aptitude for, testing the assumptions about a particular decision.
I'm also convinced that it's a relatively small percentage of people who have that cerebral wiring. For the rest the whole idea is at best uncomfortable - at worst it's just plain blasphemous.

I read some material once that talked about the roles required to have an effective team. One of those roles was someone who was described as "the pessimist". Which seems like a perjorative description. Unfortunately, it seems that's how most people feel about anyone who consistently tries to do assumption checks.

The suggestions that you've made will help that situation - as long as you can overcome (what seems to me to be) the fundamental hurdle that you will seldom find a critical mass of people in a group that will accept that this is a "Good thing to do".

There was a great line in the film "The American President" - Michael Douglas was joking around and told his staff that his girlfriend was "questioning their loyalty!". And under his breath, Michael J Fox said "I question it all the time"

Posted by: omni | Aug 21, 2006 5:37:13 PM

But...is it REALLY safe to assume that it's beneficial to challenge assumptions?

Posted by: Sean C. | Aug 21, 2006 6:34:10 PM

I totally agree that we must always challenge assumptions. Otherwise assumptions soon grow to beliefs and at one day one can not differentiate it from a fact.

How do you improve the throughput of a software system. Optimization, redesign, refactoring, migration to another platform..... ???

When was the last time you saw, thought or recommend your customer to upgrade their hardware for better throughput? Have you not assumed that customer would think your software had a problem?

I have recently seen some companies challenging those assumptions. I was shocked to know that by using Solaris 10 compiler(C++) with a new line of servers from Sun, their software is performing at almost 10 times (you read it right, almost 1000%) better.

How much are you or your customers are ready to pay for such an improvement? Again challenging the assumption, the price is just about the cost of hiring 4 junior software engineers for a month in California.

Posted by: Murali | Aug 21, 2006 7:38:09 PM

omni: I must do a better job of remembering this... one of MY assumptions (that I need to work on) is that most people DO think it's a Good Thing to do, even if it takes a little prompting. That not everyone really sees it that way might be why I missed off so many people in those meetings ; )

Sean: Is it really SAFE to challenge assumptions? For me, the real question would be, "is it really safe to NOT challenge assumptions?" And I have a hard time answering with anything but "no." I didn't say that you won't have assumptions -- and you certainly cannot prove all your assumptions before you test them, for example. But... if we don't keep challenging them to see if they still make sense (and even THAT assumes that they once did--which might not be true!), where does that leave us? I think it's far riskier to NOT challenge our assumptions and try to unearth the assumptions we've already accepted as "fact".

Murali: Excellent point -- and anything that gets a company to be more honest with customers--good or bad-- is a plus.

Posted by: Kathy Sierra | Aug 21, 2006 9:04:18 PM

Challenging assumptions? No way - takes too much time.

I´m working in the energy business. About three years ago I came up with a simple formula on how to guesstimate the energy consumption of a prospect based on data that can be easily gathered from other databases.

I had exactly one chance to rethink the approach in the last three years and I did only do a finer consideration of industry branches, because - there was no time for radically different and untested. It´s obvious that my method has flaws but when I´m told to get 1000 new prospects for the next mailing by tomorrow I´m stuck with doing what I always do.

Maybe lowly marketing assistants are not the right audience for this blog entry.

Posted by: Michael Herzog | Aug 22, 2006 1:05:50 AM

Kathy - you assume I like cupcakes! Just to clarify, I was reaffirming (having particpated in some and viewed others) that focus groups in particular are the source of some very dubious assumptions.

Michael - change companies, bosses who see mailing 1000 random prospects as superior to focussed analysis of the most valuable customers are holding you back.

Posted by: John Dodds | Aug 22, 2006 2:59:20 AM

I've been reading books about Theory of Constraints recently, and in particular "Thinking For a Change: Putting the TOC Thinking Processes to Use" by Lisa J. Scheinkopf ISBN:1574441019, (but see books by Eliyahu Goldratt for the source of these ideas). Finding and challenging assumptions is pretty central to these thinking tools, but then it is also pretty central to Lateral Thinking - see most of Edward de Bono's books, for example "Po: Beyond Yes and No" ISBN:0140137823. These tools help you move forward after you have challenged the assumptions, mostly by giving useful structures one can apply to the thinking process, which help communicate where you are going with an idea. Thus you *might* avoid the suggestion that to challenge assumptions is negative.

Posted by: hgs | Aug 22, 2006 5:33:42 AM

In my spare time I write science fiction. Written science fiction almost always involves the questioning of some assumption.

"What if this wasn't what you thought it was...?"
"What if there was another way...?"
"What if...?"

Keep writing this stuff long enough, and questioning assumptions becomes an ingrained reflex. I would also recommend that you read SF in order to exercise this ability.

BTW, here are some hidden assumptions that have been bugging me:

1. "Men's underwear is supposed to be uncomfortable."
(Why? Because men fear they might be called sissies if they asked for underwear that didn't itch, scratch or squeeze? There's a huge unexplored market here.)

2. "Women are bubble-headed idiots."
(Many, many TV commercials seem to be based on this assumption.)

3. "Old people are not interested in computers."
(Why aren't you trying to sell computers to people over 60? Is it because you think old people don't have the time, or the money, or the brains?)

4. "Car owners don't care about air pollution."
(I'm not going to buy a car until I find one that doesn't run on gasoline. Period.)

5. "Everybody just loves cigarette butts!"
(Smokers live in a fantasy-land where cigarette butts spread joy and flowers if you drop them on the ground. If someone came up with a proper technology for the disposal/disintegration of cigarette butts, the world would become a more beautiful place...)

Posted by: A.R.Yngve | Aug 22, 2006 5:53:37 AM

You're right, focus groups are often useless. What's the best alternative?

Posted by: JK | Aug 22, 2006 7:02:16 AM

Hey Kathy! I Love your blog. You're a terrific inspiration, and please don't change a thing.

Mark this one up in the "wisdom of a child" category. Every times I give my 4 year old Son A.J. an answer, his immediate response is "Why?" Usually after the 3rd or 4th answer to his "why" he's satisfied. By that time - we've gotten to the heart of the matter.

Wen I take my assumptions and keep asking "why?"... I'm often surprised by the final answer. Often for me it's some derivative of "because I said so" (with my Son) or "because my boss said so." (at work). Those are the perfect assumptions to challenge.

Posted by: Bill P | Aug 22, 2006 8:32:05 AM

Generally speaking, stereotypes suck and stereotypes lead to assumptions, and assumptions are the mother of all screw ups.

Posted by: claudiu | Aug 22, 2006 8:46:57 AM

One of the most effective assumption-busting activities I've found is blogging. Not only does the writing often force me to become more aware -- and explicit -- about my assumptions, others' comments sometimes help expose hidden assumptions.

A few other interesting examples of assumptions come to mind.

In The Tipping Point, Malcolm Gladwell tells the story about how Coca-Cola decided to go to market with New Coke based (in part) on the result of blind taste tests in which people drank sips of different formulas, presumably based on the erroneous assumption that what people most enjoy by the sip, they will most enjoy by the can (or bottle). Of course, as Read Montague demonstrated in his experiments on neuromarketing, blind taste tests may have other shortcomings, at least when it comes to heavily marketed products such as soda.

Yochai Benkler, in his book, The Wealth of Networks: How SOcial Production Transforms Markets and Freedom, invokes the wisdom of Stephen Jay Gould in observing "humnan societies exist in a series of punctuated equilibria". Individuals, organizations and societies have variable openness to challenging assumptions at different times, and while there may be some entities which are more generally predisposed toward a willingness to challenge assumptions, I believe it is something that anyone can practice (and learn).

The wisdom of Mark Twain was recently invoked by Al Gore in An Inconvenient Truth, a slight variation of which may be applicable here: "It is difficult to get a person to challenge his/her assumptions when his/her salary depends on them."

Finally (for now), of the Four Agreements proposed by Don Miguel Ruiz, I find "Don't make assumptions" to be the most consistently challenging ... as a rather pedestrian example, I don't know how I would be able to drive a car -- or walk near moving cars -- if I weren't willing to assume some amount of attention and rationality on the part of [other] drivers.

Posted by: Joe McCarthy | Aug 22, 2006 12:17:03 PM

Yes I agree with you, assumptions like to be challenged on a regular basis. I find your second proposal for checking the peopele frequently and continuously, is a very reasonable one.

Thank you for sharing your thoughts with me !

Posted by: Maria making pictures | Aug 22, 2006 1:58:10 PM

God!!! Kathy this piece is wonderful. Could it be printed by someone and sent to every candidate for the November elections. Maybe Just Maybe one of the thousands of candidates will actual check their assumptions. I'm doubtful in most cases oly the first three letters apply.

Posted by: Roger Wilks | Aug 22, 2006 10:10:50 PM

Sometimes assumptions are so ingrained in us that it becomes fighting the "establishment." It takes that rare breakout soul, the person who can stand up against the crowd and risk it all to actually make things happen.

This is why we both need corporate America and the small shops. It is also the beauty of the blogosphere.

The wiki I use to teach my students is an example. I thought wikis made sense in the classroom and did it. I didn't know that many people thought that children are not "responsible enough" to handle wikis. (They are wrong.)

The other day, I had someone in Boston call me, after our wiki was mentioned in the Boston Globe and ask, "Why aren't they doing this up here and you're innovating in the classroom in the tiny town of Camilla, Georgia.

My response was that I didn't know I wasn't supposed to be able to innovate.

The blogosphere helps us challenge assumptions more than ever as tiny pockets of innovation spring up because people (like myself) are so out of the loop, they don't know they aren't "supposed" to be able to do something.

I think the blogosphere is a great partner to assumption challengers.

Thank you for another great post!

Posted by: Vicki Davis | Aug 22, 2006 10:11:03 PM

omni wrote:

"I read some material once that talked about the roles required to have an effective team. One of those roles was someone who was described as "the pessimist."

Sounds similar to Belbin's "Monitor Evaluator" team role:


Posted by: Milan Davidovic | Aug 23, 2006 8:23:15 AM

Reminds me of a book I recently read:


Posted by: Mohamed Jamal | Aug 23, 2006 10:35:20 AM

Great post. There is a book by Betty Edwards called "Drawing on The Right Side of the Brain" that does a good job of explaining how the left side of the brain is built to quickly make assumptions and assign symbols and names to objects (that include inherent assumptions). Both skills are very useful for dealing with lots of information and "solving" problems quickly, but in a very real way they limit our vision when we're looking for truly creative solutions because we don't even realize what we are assuming. So the trick is to shift over to the right side of the brain which isn't wired to make assumptions. Your 4 tips are a good way to do that. Betty made some additional suggestions in her book. Here is a post about a few of them if you are interested: http://www.seedsofgrowth.com/have-you-tried-turning-it-upside-down

Posted by: Dave Free | Aug 23, 2006 11:26:23 PM

Hi Kathy. Once again an amazing post :)

I believe that an important aspect of being a good designer is asking "Why not do it this way?". For example, to design a new cell phone we shouldn't be thinking "Let's design the buttons and the menu". Instead, we could take a step back and think "do we really need all those buttons and that 10 level menu?". I've written more about this in How Attention Shapes Interaction Design, including a cell phone that actually pays attention to what the user is doing, and responds accordingly.

Posted by: Jim Meyer | Aug 24, 2006 1:10:29 AM

One way to force assumptions into the open is to build a model of the system under discussion. Obviously, this isn't appropriate in all situations, but when it is, a modeling technique like Discrete Event Simulation or Systems Dynamics requires that you make your assumptions explicit, or the model won't work.

Posted by: Steve Shervais | Aug 24, 2006 12:00:56 PM

I was watching "8 Simple steps" on the telly sometime back. A quote from the series.

"When you assume you make an ass out of you and me."

How very true.

Posted by: Balaji M | Aug 25, 2006 5:26:35 AM

keeping an open mind is sometimes the most difficult of tasks.

Once we believe something to be true, we tend to collect evidence to support our belief and ignore evidence against it.

It is easy to question the past, but what about our vision of the future.

Posted by: Allan Wallace | Aug 26, 2006 6:34:55 PM

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