Nov 1, 2015   #Jeff Raskin 

Yesterday, I drove an automatic for the first time. When driving a manual shifter, my brain is on auto pilot - I’m seldom aware of my gear shifts and footwork. When I drove the automatic, all of this suddenly needed to be consciously done. So there was a bit of struggle I experienced with a supposedly simpler system. Bleh! The automatic drive is not intuitive.

Now, wait a minute. We know that folks who shift (ahem!) from automatic to manual face a harder struggle. In the software world, there is a similar hurdle faced by folks shifting between operating systems, and yet we see wars of the kind “my OS is more intuitive than yours”. What do people mean when they say something like that?

Jef Raskin came up with a suggestion that addresses this use of “intuitive”. In, what is in my opinion, a very important article in HCI, he declares that “intuitive equals familiar”. Whenever people talk about some control system being “intuitive”, we simply replace the word “intuitive” with “familiar” and we won’t be far off from what they actually mean. “In-tuit” can be interpreted as what comes without teaching - is “untaught”. This fits with “tuition” being the word for being taught.

In my case, my declaration would read “The automatic drive is not familiar (to me).” Of course it isn’t, and that perfectly well explains my initial struggle with it. The rewrite immediately clarifies what I actually meant, and as a bonus points out that my judgement has been needlessly generalized. Using “familiar” instead of “intuitive” has helped me correctly attribute my judgement to be about myself rather than be about the system I’m talking about. I’ve been using Raskin’s theorem, as I prefer to call it, successfully for many years to keep my eyes on the ball whenever it comes to design, and taking away much of the mysticism that surrounds “intuitive interface design” in software, as though it were an exclusive insight shared by a few select sages of the field.

Depth of familiarity

What about the design of the iPhone “momentum scroll” interaction? None of us have ever seen anything like that in an interface to a computing device at large. We were more used to scroll bars everywhere, and yet I don’t think that anyone would disagree with the statement that momentum scroll is “intuitive”.

To resolve this, we need to break down our experiences into various depths of familiarity -

  1. Recent cognitive familiarity. This is about what we’ve experienced recently and is still fresh in our experiential memory. Fresh enough to just reuse whatever we did in our recent experiences without thinking twice about it.

  2. Invested cognitive familiarity. As we grow and school, we put in a lot of cognitive effort into learning certain “technologies”. This includes the ability to read, write and speak in one or more languages, the ability to use pencil and paper as tools that help us think, an artist training to paint using brushes and oil paints, the decimal place value system, and so on.

  3. Physical familiarity. We learn to walk, to use our hands to move and manipulate objects much before we consider computers and we learn this when still very young. We’re, to a good extent, also biologically wired to learn this stuff early.

  4. Evolutionary familiarity. We’ve genetically evolved to adapt to our environment. Any situation that falls in the domain that we’re evolved to adapt to will feel very familiar to us. Examples include face recognition, identifying and tracking eyes in other humans and creatures.

Recent cognitive familiarity can change quickly. Invested cognitive familiarity likely decays only after long periods of disuse. Physical familiarity is essential for our existence and likely lasts us through our lifetime, and evolutionary familiarity can be sustained across several generations.

Momentum scroll, I think, falls in the area of “physical familiarity”. We’re used to seeing things move for a while after we give them a push, and eventually stop due to friction. So even though we haven’t seen a computer interaction like that before - i.e. we don’t have recent or invested cognitive familiarity with it - we’re more deeply familiar with it through our interactions with real world physical objects. This correspondence doesn’t have to be literal, which permits us to momentum scroll through “infinite lists”.

One way to test this explanation would be to make the scrolled object move in the direction that is opposite to the direction of the finger movement, and then test with fresh minds which version they find easier. I’m willing to bet that it is easier for folks to pick up when the direction of movement is aligned with the direction of swipe, though I also think that given enough time and effort, people do have the capability to learn the opposite movement to the point of effortless use as well. We may all find pencil and paper easy to use, but easily forget the sheer effort a kid needs to make and the many years it takes before sufficient mastery of these “simple” tools is attained.

“3D touch”

In the iPhone 6S, Apple introduced force sensitivity as another dimension of interaction, calling it “3D touch”. A light touch on an app icon now reveals quick actions to perform or quick status reports. A heavier push+hold may show more information. This is cool!

When I tried the force touch interactions, I had to experiment quite a bit before forming a reasonable mental model about what I can expect apps to perform. In this case, unlike momentum scroll, I think Apple tapped into another level of physical familiarity, but is banking on our ability to learn quickly with a little investment on our part.

What might be an example of an interaction using force sensitivity that might actually feel “intuitive”? We’re familiar with applying force on a stamp to get it stuck on to an envelope. So if Pages adds an interaction where you push harder on an image to cause the image to be stuck relative to the page position instead of moving along with the text, that might (I’m only guessing) create an “of course it works that way” feeling.

Paper and the iPad Pro

One of my favourite apps is Paper and I can’t wait to try it out on the iPad Pro. Many years ago, I’d wished for an iPad that had a Wacom tablet-like precision and utility of a pen-based interface and I’m happy to see it has come into reality, at least as far as the descriptions I read about the iPad Pro. I love physical pencil/pen/paper - both for writing and doodling. So I expect that the iPad Pro will tap on my invested cognitive familiarity.


We might wager that the deeper the level of familiarity that we’re reaching into, the more “intuitive” our design will feel to users. So what kind of an interface might exploit evolutionary familiarity?

Diet control is a serious problem for many folks. We have a tongue that doesn’t seem to be able to resist sweet and oily things. In today’s urban life style, too much sugar/calories/fat is a no no.

(Warning: Brace yourself for some wild hand waving and imagination here!)

Consider a tongue “sleeve” connected to a food monitoring system that can give pleasurable culinary sensations when we eat stuff that is supposed to be good for our health and unpleasant sensations when we eat things that aren’t. What if bitter gourd juice can be made to taste mildly sweet, and anything with refined sugar made to taste bitter? Would you have much difficulty using such a system to control your diet? I don’t think I would find it hard at all, and guess I would be able to use it effectively from day one.

The tongue is not the only factor since smells also affect our attraction to food, but I think you might get the point here without me going any further.

Value to design process

Identifying these depths of familiarity is, I think, a useful tool to bring into the product design process. We can now evaluate which depth level we’re operating at when we’re designing an interaction. The breakthroughs happen when we dive really deep, as happened with the touch interface design introduced in the original iPhone.

Now go and make stuff that taps deeply into our evolutionary familarity.

PS: I focus largely on Apple products in this post and might come across as a fan boy, which in some ways I am. This is not to discount the work done by so many giants preceding these products, but merely to present relatable examples for what I’m talking about.