There are many elements of Interaction Design: it requires a user-centered mindset and also knowing some parts of cognitive psychology (like how mental models work, and what are the affordances). We should take into account how the human mind works, for example:
- what are the limitations of our visual perception
- how we remember things
- how can we reduce the cognitive load
- how to support the way we consume information (e.g. with progressive disclosure)
- how to manage the user errors
- how can we maintain the users' attention.
It is also important to know the most common user interface patterns.