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Designing Interactions

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Psychological Principles

3:05 with Hope Armstrong

There are several laws in Interaction Design. These psychological principles help guide designers to make intuitive user interfaces. We'll look at three popular laws: Hick's, Fitts's, and Tesler's.

The field of interaction design consists of several psychological principles. 0:00
In this video, we'll take a look at three laws, 0:05
Hick's Law, Fitts's Law and Tesler's Law. 0:09
Hick's Law states that the more choices a person is presented with, 0:14
the longer the person will take to reach a decision. 0:18
It was defined by psychologist William Edmund Hick. 0:22
Applied to design, 0:25
this means user interfaces should be created with simplicity in mind. 0:27
Make content interactive and provide categories, sorting, filtering and 0:32
sections to allow the user to narrow down what they'd like to see. 0:38
This reduces cognitive load and makes it easier to use the products. 0:43
Next up is Tesler's Law. 0:48
It was articulated by Larry Tesler, 0:51
a computer scientist who works in the field of human computer interaction. 0:53
It states that for 0:58
any system there's a certain amount of complexity that cannot be reduced. 0:59
While Hick's law states user interfaces should be simplified, Tesler's law 1:04
knows that there's a certain point where a product cannot be simplified any further. 1:09
Let's imagine an ecommerce shop. 1:15
You can simply visit the website and add products to your card, that's easy. 1:18
There's no need to enter any billing or shipping information yet. 1:23
But when you're ready to check out, 1:28
the store will need payment and they'll need to know where to ship the order. 1:30
Okay, so that's where the inherent complexities lie. 1:35
But even so, several decisions can be shifted to a back-end process, and 1:38
it's up to you as a UX designer to identify these opportunities. 1:43
Perhaps as the user enters their address the system offers recommendations 1:48
to auto-complete the street name, city, state and zip code. 1:52
Even better, this serves a dual purpose of ensuring the address is validated. 1:58
There can also be an option to create an account, 2:03
which would save the previously entered information for next time. 2:06
The last law we'll look at is Fitts' Law. 2:10
Coined by psychologist Paul Fitts, it states the amount of time required for 2:14
a person to move a pointer to a target area 2:19
is a function of the distance to the target divided by the size of a target. 2:22
Now, that's a lot of logic to make sense of. 2:28
To put it in simpler terms, a target area that's small and far away 2:31
will take the user more time to interact with than one that's larger and closer. 2:37
It sounds like common sense, but 2:42
it's laws like these that help inform design decisions. 2:44
This is just a sampling of the laws you will encounter in the field of 2:48
interaction design. 2:51
If you're hungry for more, check out the teacher's notes. 2:53
May these principles guide and inspire you in your next project. 2:57
In the next video, we'll look at sensation and perception. 3:01