Perception is what the user see's and feels when they are using a HCI. To help us see, feel and use a HCI designers use colors, patterns and objects.
Colour can determine if the user should be careful or not, or if the user need to take action within the HCI, or it can also tell the user that there is nothing to worry about. Designers use color to help users use HCI's. It is natural for us as humans to think that red means dangerous, yellow means be careful and green means that everything is fine, and designers use this to their advantage and to help us make HCI's more easy to use.
As well as drawing attention to users and notifying users, color is also used in HCI's to improve navigation. By using colors consistently it can help users to navigate to find the right information.
Patterns are also used in HCI to widen the users experiences of using the HCI. Designers use many different patterns and ideas to make HCI's easier to use.
Designers use proximity to make items and windows appear closer then others. An example of this is if you have 2 windows open in an operating system you are actively using 1 window, this window will appear closer then the other window.
Designers also use continuity to indicate to users that something is working or thinking, an example of this is when you are uploading a photo to Picassa via an android phone, a bar will appear with a pattern inside moving left to right indicating that the computer is continuously working at the moment.
Designers also use similarity a lot, for example on an IPhone, if 2 apps are similar and work together or the user needs to use both applications to produce a product or result then the icons for the applications will look very similar.
HCI designers also use objects to help users to interact with HCI's. They quite often use 3D shapes to help users to interact with HCI's. Instead of using 2D shapes which can be seen as boring they use 3D versions of the shapes, these could be arrows or just normal shapes, but 3D makes objects look more interesting meaning the user would be more happy using the HCI because it's more interesting. 2D objects are also widely used in HCI's because of how easily recognizable they are. Many different objects are used in HCI's such as squares, circles and arrows. The human brain can process 2D shapes very quickly meaning that users can interact with very quickly when the shapes are in the form of interactive material or hyperlinks.