Should user behavior dictate design or design dictate user behavior?
Usually its a blend - where you design for an expected use case and behavior - but then involve users early enough in the process to understand how they will choose to use it. The best example I can give you is how a custom architect works:
They get a design program from the client (ie a functional spec)
They then produce a design
The client gives them feedback on the design
The revised design gets built
Then the Client lives in the house and uses the spaces as THEY see fit.
Much has been made of Steve Jobs' and Jonathan Ives' singular visions for the iPod and iPhone - but its important to recognize that NEITHER product was revolutionary. Each was actually an evolutionary design product vs. what was in the marketplace. (heck that's even true of the original Mac UI and Mac Personal Computer).
There were plenty of MP3 players in the market before the iPod. So Ives and Jobs could - and did - study how users used them, what worked, what didn't, what users liked, what users were trying to do but could not.
So in so many ways, both for the iPod and iPhone, some of the most iconic "revolutionary" products out there - there was no revolution. USERs dictated the design and they were evolutionary rather than revolutionary designs
As Dimitrios pointed out, the designs Ives and Jobs came up with resonated emotionally. but that emotional response was the USER dictating how things should be - through his/her emotions
To my understanding, anything new invented all throughout the history was to make Human's Life easy and better. Human's in your case is the User.
Your Question is similar to two sides of the same Coin.
a) Design Dictates the User Behavior
This happens when you have invented something which has never existed before. In this case you can dictate the "User" to some extent or over a period of time because this is when the people start using your product. After a period of time, use start bring in new ideas in the product, this is where we need to look into the other side of the coin.
b) User Dictates the Design
Design is always a set of ideas, when implemented makes
products more user friendly for the "User" to use them.
Earlier, we used to have computers which were so big and over a period of time, the demands of the "Users" have increased which led to the innovation of Laptop and now smartphones.
That's why it’s always said that the CEO of any company need to have those futuristic thoughts or ideas to make products as user friendly as possible.
So, I think it depends upon whether you are an inventor or an implementer of an existing invention.
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