The interdependence of living things for sustainable design
Designers need to understand the issues that will affect the environmental condition of the planet as well as the interconnected social and economic systems that we need to sustain.  An evolving area.

The human condition, for global design
Products that are designed for a global market place need will need to be informed by information on cultural variation: culturally appropriate colours, logos are only a few basic examples.

The way people relate to one another, for the design of connected systems
Connectivity is now a part of many design problems: designing services for delivery through the internet is where sociological knowledge will help inform the problem.

The way the mind works, for the design of human computer interactions
Much has been written in cognitive psychology about how an individual interacts with machines – these studies formed the basis of human computer interaction.

The way the body works, for the design of physical man-machine systems.
Consider this constraint include what the person is doing as well as the things they are using. eg keyboard design

The sizes of people, for the design of physical objects

See: Tilley,A. & Henry Dreyfuss Associates (2001)
The Measure of Man & Woman: Human Factors in Design, Revised Edition I Wiley Publishing, Indianapolis,