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The field of interaction design consists
of several psychological principles.

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In this video,
we'll take a look at three laws,

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Hick's Law, Fitts's Law and Tesler's Law.

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Hick's Law states that the more
choices a person is presented with,

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the longer the person will
take to reach a decision.

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It was defined by psychologist
William Edmund Hick.

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Applied to design,

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this means user interfaces should
be created with simplicity in mind.

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Make content interactive and
provide categories, sorting, filtering and

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sections to allow the user to narrow
down what they'd like to see.

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This reduces cognitive load and
makes it easier to use the products.

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Next up is Tesler's Law.

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It was articulated by Larry Tesler,

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a computer scientist who works in
the field of human computer interaction.

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It states that for

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any system there's a certain amount
of complexity that cannot be reduced.

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While Hick's law states user interfaces
should be simplified, Tesler's law

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knows that there's a certain point where a
product cannot be simplified any further.

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Let's imagine an ecommerce shop.

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You can simply visit the website and
add products to your card, that's easy.

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There's no need to enter any billing or
shipping information yet.

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But when you're ready to check out,

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the store will need payment and they'll
need to know where to ship the order.

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Okay, so that's where
the inherent complexities lie.

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But even so, several decisions can be
shifted to a back-end process, and

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it's up to you as a UX designer
to identify these opportunities.

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Perhaps as the user enters their address
the system offers recommendations

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to auto-complete the street name,
city, state and zip code.

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Even better, this serves a dual purpose
of ensuring the address is validated.

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There can also be an option
to create an account,

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which would save the previously
entered information for next time.

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The last law we'll look at is Fitts' Law.

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Coined by psychologist Paul Fitts,
it states the amount of time required for

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a person to move a pointer
to a target area

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is a function of the distance to the
target divided by the size of a target.

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Now, that's a lot of
logic to make sense of.

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To put it in simpler terms,
a target area that's small and far away

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will take the user more time to interact
with than one that's larger and closer.

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It sounds like common sense, but

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it's laws like these that
help inform design decisions.

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This is just a sampling of the laws
you will encounter in the field of

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interaction design.

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If you're hungry for more,
check out the teacher's notes.

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May these principles guide and
inspire you in your next project.

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In the next video,
we'll look at sensation and perception.