The User, The individual

Ockam, Hicks & Fitts 

Ockham's Razor

Ockham's Razor is the 14th century principle by William of Ockham, which translates to: Entities should not be multiplied unnecessarily. Keep it simple both for the design and the information.

Fitts' Law

In 1954 Paul Fitts proposed the theory that the time required to move to a target is a function of the distance to the target and the size of the target. This law has become  a basic in the field of human-computer interaction. Constrain distance between pointable elements and increase the size of the element.

Hick's Law

Hick's Law, is named after psychologist William Edmund Hick. It deals with response time and the amount of options.

It states that the time it takes an individual to make a selection increases as the amount of options increases.
Tests have shown that when an individual has too many choices the result can be that they make no choice at all.

Customers given too many choices are 10x less likely to buy  Sheena Iyengar

Limit the amount of options you give to the user to complete a task